Spinoff : general ABS discussion

[Rebelrocker]

It seems there is no ABS system on the cars in this test patch, only anti lock brakes. This can be seen when braking with left wheels on grass, right ones on tarmac.

A real ABS system doesnt make the car nervous and make it turn due to traction differences, this is what ABS was developed for in the first place, anti lock is just a part of it.

Nice work so far tho i like it:)

[xaotik]

A real ABS system doesnt make the car nervous and make it turn due to traction differences, this is what ABS was developed for in the first place, anti lock is just a part of it.

You're probably thinking about modern stability control (ESC) systems that contain ABS. ABS stands for "anti-lock braking system" and as that, that's all it normally does. Newer electronic aids added to cars in the form of ESC contain ABS as a part of them, not the other way around.

[Rebelrocker]

Nah, ESC is just for preventing loss of car control by messing with with the cars brakes even if you dont want to etc. ABS systems work by not letting a wheel move slower than other wheels, moving the brake pressurr away from the wheels that move slower or want to lock up. This is why you feel the vibration at the pedal.

A ABS car with 2 left wheels on ice and 2 on tarmac wont stop fast, but it stops straight, a bit like a differential

[de Souza]

I'm with xaotik and perhaps you mean EBD - Eletronic Braking Distribution?

As far as I know ABS is just anti-lock and will screw things when tyres have different grip levels.... I reckon an ABS braking test made by a brazilian maganize ages ago with a Fiat Tempra, one of the tests was to brake with left tyres on dry tarmac and right tyres on wet tarmac, resulting in loss of control. Also on irregular surfaces the braking distance was much longer than without ABS.

I might be talking rubbish though. :tilt:

[bbman]

I remember when I had to do my mandatory driver safety training, there was an A-Series Merc (before the facelift), which stopped straight on uneven surfaces, developed just a slight wiggle... I don't know if the first A-Series already had ESC, it was before ESC was declared the nonplusultra of safe driving...

[vrooom]

ABS is what let you STEER while you BRAKE HARD around obstatles such as a crashed car or dead person on road instead of locked up wheels and skidding into it.
they make your braking distance longer due thier on/off/on/off nature instead of grabbing the disc brakes and locking up the wheels, reducing the chance of skidding into stuff. That why it gave vibration on the pedal.

That all to it.

Hope you understand me.

[Rebelrocker]

It seems the common misconception really is common. here's some ABS reading.

http://www.nr1.lt/NR1-Discovery/Brakes/ABS/abs.html

Bosch also, who produces seems to agree with me

http://www.bosch.com/assets/en/company/innovation/theme03.htm

[NightShift]

I don't know if the first A-Series already had ESC, it was before ESC was declared the nonplusultra of safe driving...

If I'm not mistaken, the A Class was the first production vehicle in Europe to feature ESP, that was because the sorry excuse of a (posh) car failed the elk test.

As a result of this unfortunate event (which surfaced after the aforementioned sorry excuse had already entered production), Mercedes had to recall all the vehicles to fit ESP, while IIRC the newly produced cars also had modified suspensions.

Subsequently, all the posh moms could feel safe to show off their glorified shopping cart when bringing their kiddies to the kindergarten on a leather upholstered baby seat.

[Syfoon]

ABS is what let you STEER while you BRAKE HARD around obstatles such as a crashed car or dead person on road instead of locked up wheels and skidding into it.
they make your braking distance longer due thier on/off/on/off nature instead of grabbing the disc brakes and locking up the wheels, reducing the chance of skidding into stuff. That why it gave vibration on the pedal.

That all to it.

Hope you understand me.

ABS cuts stopping distances, not lengthens them.

Remember, your tyres don't grip if they're locked up. If they don't grip, you don't have any friction/rolling resistance, so you don't slow down.

Locking up is sliding. Sliding when stopping is bad.

I thought everyone knew this :really:

[vrooom]

ABS cuts stopping distances, not lengthens them.

Nope you got it wrong. :really: manafuctor go around this 'problem' by installing bigger brake discs.

[ColeusRattus]

ABS cuts stopping distances, not lengthens them.

Remember, your tyres don't grip if they're locked up. If they don't grip, you don't have any friction/rolling resistance, so you don't slow down.

Wait what? Do cars levitate as soon as they lock their tyres? While it is true that a skidding tyre isn't using its MAXIMUM potential to brake, it still is a very efficient way to stop. Only you can't steer while skidding to a halt.

[MikeB]

Gee, it gets so boring to read the same arguments about what ABS is and what not on every single page again...

[Syfoon]

Nope you got it wrong. :really: manafuctor go around this 'problem' by installing bigger brake discs.

In most of road grip conditions ABS system lets you to decrease braking distance.

So you're saying you slow down quicker and within less distance if you stamp on the brakes, lock up the brakes and slide down the road?

You're on drugs fella.

Wait what? Do cars levitate as soon as they lock their tyres? While it is true that a skidding tyre isn't using its MAXIMUM potential to brake, it still is a very efficient way to stop. Only you can't steer while skidding to a halt.

Perhaps my usage of the word "any" was incorrect :p

[Shotglass]

It seems there is no ABS system on the cars in this test patch, only anti lock brakes.

because thats what abs is and stands for

A ABS car with 2 left wheels on ice and 2 on tarmac wont stop fast, but it stops straight, a bit like a differential

no it wont... not unless you steer against the car turning away from the slippery stuff

[Michel 4AGE]

no it wont... not unless you steer against the car turning away from the slippery stuff

That shouldn't be the case in a more modern/new car with a proper wheel-independant ABS system. Todays cars have much better ABS controllers (much like the engines ECU) with much higher pulse rates and often work in conjunction with ESP. Older cars with 2-channel ABS however need driver input like you said..

[Rebelrocker]

because thats what abs is and stands for



no it wont... not unless you steer against the car turning away from the slippery stuff

I must say your stament is ridiculous sorry. If you would take the time to atleast read what bosch has/is been implementing on cars for ages you would know.

Its absolutely absurd that you come with those stamements that have no basis on anything.

Do you disagree with bosch that impements ABS in many German cars for example, they state the following:

Situation 1: With ABS, your car stays on track - even on a road surface that is icy on one side

Now there is always marketing tricks and all that, but saying that bosch is faking is just far fetched in my opinion.

Here in Finland we have safe driving/slippery training that is mandatory after 2 years of having a license. In this test we are braking with both ABS and without ABS, on the same car.

And i assure you braking without ABS on uneven surface takes loads of brake pumping and correcting the car, whereas if the ABS line is connected and operational you can just stomp the brake and think about what you like the most:)

This stuff is quite simple car knowledge, i realize im not discussing in a mechanic forum, but im sure many of you have experience in both ABS and non ABS cars first hand.

Wait what? Do cars levitate as soon as they lock their tyres? While it is true that a skidding tyre isn't using its MAXIMUM potential to brake, it still is a very efficient way to stop. Only you can't steer while skidding to a halt.

It is true while you have a surface that is solid you stop faster by not completely locking the wheels. But on uneven surfaces like Sand, Snow or any loose stuff you'd want to "dig" the wheels in it, which ABS will not allow.

I must once again resort to quoting stuff im sorry but Wikipedia mostly from several sources states for example:

"In gravel, sand and deep snow, ABS tends to increase braking distances. On these surfaces, locked wheels dig in and stop the vehicle more quickly. ABS prevents this from occurring. Some ABS calibrations reduce this problem by slowing the cycling time, thus letting the wheels repeatedly briefly lock and unlock. The primary benefit of ABS on such surfaces is to increase the ability of the driver to maintain control of the car rather than go into a skid — though loss of control remains more likely on soft surfaces like gravel or slippery surfaces like snow or ice. On a very slippery surface such as sheet ice or gravel, it is possible to lock multiple wheels at once, and this can defeat ABS (which relies on comparing all four wheels, and detecting individual wheels skidding). Availability of ABS relieves most drivers from learning threshold braking".

Source wikipedia

Nope you got it wrong. :really: manafuctor go around this 'problem' by installing bigger brake discs.

This is probably sarcasm from you, but locking wheels has been easy ever since they invented disc brakes, the trick is not to overheat them.

Sure you can get your Cortina/Taunus or even a Cadillac to lock its wheels, trick is, what are you going to do when you stop from lets say 200kph, or stop from 100 or so several times during a hot summer.

Its about cooling and brake feel, everyone can make brakes oversensitive. Making them reliable at all times is a different story.

Sorry fellas for posting like a madman, but i enjoy a good discussion, and Live For Speed has the best Tyre model ive seen yet anyway, so its close to my "heart" heh.

[S14 DRIFT]

It's already common knowledge that ABS was designed to allow drivers to remain in control on their vehicles in emergency stops. It was not designed to reduce stopping distances . However, this is a bi-product of both poor driver skills, badly maintained cars (tyres, pressures etc) and roads which aren't always in the best of condition. Generally for 90% of drivers, ABS will stop you faster.

[Stang70Fastback]

no it wont [stop straight]... not unless you steer against the car turning away from the slippery stuff

Obviously you aren't speaking from experience.

Either that or you really should have your ABS systems checked out. That's the WHOLE POINT of ABS, lol.

[Shotglass]

Obviously you aren't speaking from experience.

i am speaking from experience
and as others have said its perfectly normal behaviour for a 1 or 2 channel abs which is exactly what lfs simulates

Either that or you really should have your ABS systems checked out. That's the WHOLE POINT of ABS, lol.

1) youre using lol as punctuation
2) the whole point of abs is to keep the car steerable not to make it brake straight with a dead person on the wheel

[Pellick]

Seems you guys have finished discussing this topic, but I'd just like to add my opinion on wether ABS reduces stopping distance or not. When I took driving lessons I was taught that "on/off" braking (stomping the pedal repeatingly) will give you a shorter braking distance than full lock up because the tyres do give maximum braking efficiency for a short moment before they start to slide. You'll feel this if you try it on a slippery surface. The ability to steer while braking is an added bonus to this technique. This is as most of you know what ABS does, just a lot faster than you can do with your foot.
Constant optimum pedal pressure (guessing it's called threshold braking) of course gives even shorter stopping distances but it's harder to do right.

In all my old cars without ABS I always used the stomping technique to stop faster on snow and ice, and I have yet to have a real crash (knock on wood).

[xaotik]

Pellick, for what it's worth the term for what you describe is "cadence braking."

[Pellick]

Hey, thanks! Didn't know it even had an English name :)

[DragonCommando]

Nope you got it wrong. :really: manafuctor go around this 'problem' by installing bigger brake discs.

Thats the second time I've seen someone say that.

Please tell me how bigger brake disks are going to do anything if the current brakes already use up all the traction the tires can give?

Simple answer, THEY CAN'T.

[Not Sure]

Unless they're MAGIC :shhh:

[emreerokyar]

Wait what? Do cars levitate as soon as they lock their tyres? While it is true that a skidding tyre isn't using its MAXIMUM potential to brake, it still is a very efficient way to stop. Only you can't steer while skidding to a halt.

taken from wikipedia:

Dry friction resists relative lateral motion of two solid surfaces in contact. Dry friction is also subdivided into static friction between non-moving surfaces, and kinetic friction (sometimes called sliding friction or dynamic friction) between moving surfaces.

i don't get why i didn't see anyone else saying something about this fundamental subject of physics. yes i know that everyone has said something about a skidding tyre which has lost its grip but nothing about a more basic concept such as those above, static and kinetic friction forces. at least i guess no one else has used these two words, did they? am i the only one who cares about these :P

correct me if i got it wrong but they teached me in my physics lessons that the static friction coefficient was usually larger then the kinetic friction coefficient. which accordingly makes me think that a braking car with tyres which are not skidding (not using their kinetic friction forces while making the car decelerate) should let the car stop easier compared to a tyre which is skidding, not always but in some conditions.

also taken from wikipedia:

For a given pair of surfaces, the coefficient of static friction is usually larger than that of kinetic friction; in some sets the two coefficients are equal, such as teflon-on-teflon.

so i think that there still is a friction force for a tyre skidding, Syfoon :) ColeusRattus is right, they don't suddenly start to levitate :P although it might not be as big as a tyre compared which is not skidding and using the static frictional coefficient.

[Shotglass]

the reason why no one used these terms is because its like holding up a flag with "i dont know the fist thing about tyre physics" written on it

[legoflamb]

Unless they're MAGIC :shhh:

Finally, now people can get your name's reference with your pic. BTW I think the United States of America is very damned near that point right now!

on topic:
anyway ABS is for people who mash the brakes with out understanding of the general dynamics of traction and lock up causing the inability to steer. Old abs, like what would be used in cars similar ot the ones in LFS, if they had any, would just pulse the brake so the front tires are not sliding all of the time.

The braking lines would look like this.

--- -- ---- --- --- ---
--- --- --- --- --- ---

^^
that is "skid - roll - skid - roll..." etc.

[Zen321]

Threshold braking makes you stop faster than the ABS. Simply because you are using the maximum brake force power on your tires at all times. It's less easy to do than cadence braking or using ABS, but at least you control the car, not an electronic device ;)

[freddyalek90]

[...]at least you control the car, not an electronic device ;)

If I'm really honest, I don't think that you really control your car without any external aid, even without abs.
What about power-brakes and power steering?

[Not Sure]

For a given pair of surfaces, the coefficient of static friction is usually larger than that of kinetic friction; in some sets the two coefficients are equal, such as teflon-on-teflon.

Rubber thas some weird properties, so it may not work that way. Tyre physics are super complex.

[sgb27]

Threshold braking makes you stop faster than the ABS. Simply because you are using the maximum brake force power on your tires at all times. It's less easy to do than cadence braking or using ABS, but at least you control the car, not an electronic device ;)
It is physically impossible to control the brake pressure to keep maximum braking force constantly. If you do manage to acheive the maximum for an instant then you will not be able to hold it there, any tiny variation in road surface or foot pressure will push the tyre over the "crest" of max friction and you will be on a postive-feedback loop to locking the wheel - and there is no way you can react quickly enough to prevent straying away from the max.

In reality I think you can control the pressure to achieve say 95% max braking power, because that way if you go slightly over you are not "falling off" the other side of the crest where the wheel very rapidly starts to lock. In the wet the "fall-off" is even steeper, so you probably can only acheive 80-90% max braking without risking an almost locked wheel.

As to whether constant 95% braking power is better than an ABS system can acheive is another matter.

[McTw1st]

If I'm really honest, I don't think that you really control your car without any external aid, even without abs.
What about power-brakes and power steering?

i beg to differ, he said Electronic device, neither power brakes and power steering is electrical their vacum/hydraulic

[freddyalek90]

i beg to differ, he said Electronic device, neither power brakes and power steering is electrical their vacum/hydraulic
OK, so if ABS was mechanical (and early ABS systems were) it wouldn't be a problem? I don't think he agrees to this. He doesn't want a(n) electronic / mechanical / pneumatic / hydraulic device to interfere on his driving, full stop.

IMHO, that's just stupid. On race tracks, that would make (some) sense, but on normal roads...

[DragonCommando]

Where do you get that early ABS systems where mechanical?

They've always had an electronic component to them, there's no way they could function completely mechanicaly. ABS only exists because of the electronic technology that makes it work.

[freddyalek90]

Where do you get that early ABS systems where mechanical?

They've always had an electronic component to them, there's no way they could function completely mechanicaly. ABS only exists because of the electronic technology that makes it work.

"[...]A fully mechanical system saw limited automobile use in the 1960s in the Ferguson P99 racing car, the Jensen FF and the experimental all wheel drive Ford Zodiac, but saw no further use; the system proved expensive and, in automobile use, somewhat unreliable. However, a limited form of anti-lock braking, utilizing a valve which could adjust front to rear brake force distribution when a wheel locked, was fitted to the 1964 Austin 1800.[...]"
Source: http://en.wikipedia.org/wiki/Anti-lock_braking_system

[DragonCommando]

"[...]A fully mechanical system saw limited automobile use in the 1960s in the Ferguson P99 racing car, the Jensen FF and the experimental all wheel drive Ford Zodiac, but saw no further use; the system proved expensive and, in automobile use, somewhat unreliable. However, a limited form of anti-lock braking, utilizing a valve which could adjust front to rear brake force distribution when a wheel locked, was fitted to the 1964 Austin 1800.[...]"
Source: http://en.wikipedia.org/wiki/Anti-lock_braking_system


Wow, that saw such limmited use I don't think thats realy a valid point here. It is interesting though. I've done alot of research in brakes and I've never heard of that system.

[sluffboy]

for a second i thought we were talking about these abs...http://images.google.com/imgres?imgurl=http://msnbcmedia.msn.com/j/msnbc/Components/Photos/061221/061221_abs_hmed_2p.hmedium.jpg&imgrefurl=http://burn-stomach-fat.blogspot.com/2007/07/three-ways-to-burn-stomach-fat.html&usg=__y2uXMR8Elam3wqbLG44rXmYB1OU=&h=259&w=423&sz=11&hl=en&start=7&um=1&tbnid=28K_yfpuBOubjM:&tbnh=77&tbnw=126&prev=/images%3Fq%3Dabs%2Bstomach%26um%3D1%26hl%3Den%26sa %3DN

:shrug:

[diNOSaur]

:biggrinfl

[Zen321]

Interesting point

Once you know the car well enough and used to such technique, threshold braking is possible. If you look at the WRs in LFS (especially the formulas') you can see that when they trailbrake, they release the brake progressively as they steer, to allow directionnal power and braking power to perform at the same time. The wheels are at the very verge of blocking, and I'd call that luck if it was on one corner, but not in every single one of the track ;)

Once you're used to the car and its behaviors on different kind of tracks, then I'm pretty positive you can threshold brake very often and be more efficient than an ABS system.

[legoflamb]

The problem with ABS and racing is the point when the computer programing is doing more than the driver. Eventually all brakes have to be are a single button press and the computer calculates the maximum coefficient of friction at any given moment and hold the grip of the tires at the peak. and where is the fun in that.

Or better yet keep the pedal for the range but make the driver unable to brake past the tires maximum with the computer. the same goes with traction control and automated steering. And it is completely possible right now.

This would change racing from real driving skill to just timing inputs into some computer.

Or how about just remove the driver altogether and have the GPS coordinates of the track programed into the computer, and watch useless machines go around in circles with no reason why one would or could be better than the rest.

All that would be fine on public roads with where there should be no competition.

[Napalm Candy]

legoflam you don't has tried ABS in LFS. You can't to be faster with ABS you will be slow (if you are a "good" racer)

[zeugnimod]

legoflam you don't has tried ABS in LFS. You can't to be faster with ABS you will be slow (if you are a "good" racer)

I must suck then.

With RB4, I am around half a second faster with ABS than without on most tracks.

[Whiskey]

legoflam you don't has tried ABS in LFS. You can't to be faster with ABS you will be slow (if you are a "good" racer)
I would say you are equl or a bit better with ABS on. Maybe in rallycross it could make you lose time. But the times are quite similar. At least for me

[Trebuh]

Hello guys!

the reason why ABS reduces brake distances is the friction coefficent of static and kinetic friction are different.

the static friction coefficent for rubber on dry/wet tarmac is about 0,8/0,5
and the kinetic friction coefficent for rubber on dry/wet tarmac is about 0,5/0,3
(taken from my "tafelwerk":smileypul)

simplyfied:
brakedistance ~ maximum brake force (applied to the tyre surface) * friction coefficent

that means braking with static friction leads to a shorter distance than braking with kinetic friction

when ABS jumps into action it keeps the tyres on the static friction level to decrease the brake distance by avoiding sliding. Because of the inertia of the car, the car stays in this better friction level while the system is adjusting.

my 10 year old car's abs adjusts more than 10 times a second (estimated value) show me the guy which is faster in pumping a pedal in a stressful situation.

please dont post ABS increases brake distance anymore, its just wrong (for tyre on tarmac-like surfaces)

ps: ~ means proportionality (i dont know how you've learned it at school)
thanks LEO for translating the physics-words

[NightShift]

With RB4, I am around half a second faster with ABS than without on most tracks.

I only have seen a positive difference from ABS on bumpy surfaces, either because the human driver applies less brake to avoid locking, or cos the driveability of the specific setup/car is impaired under braking. Does that fit within your experience?

[S14 DRIFT]

I must suck then.

With RB4, I am around half a second faster with ABS than without on most tracks.

That explains it!! :razz:

[DragonCommando]

Nobody can dispute that on dry flat tarmac ABS stops shorter, but thats not the point of ABS, the whole reason behind ABS is to allow you to steer while you brake under maximum force. It prevents you from running into the accident or obstruction infront of you.

Older ABS is a good example of this principal reason for its existance, older ABS only acted on the REAR wheels, this was to prevent people from switching ends when they tried to avoid an obstruction in the road.

The problem that became apearent very early on was that people wouldn't just end up locking the rears, they would panic and lock all four tires and slide into the object the ABS was trying to help them avoid. So ABS was put on all four wheels and the end resault is a bunch of miss educated drivers that belive ABS is there to help them stop, which it is NOT.
I can't state this with enough force, ABS IS NOT TO HELP YOU STOP, IT HELPS YOU STEER!

Even the Starion had ABS on only the rear wheels.

[Neilser]

Hello guys!

the reason why ABS reduces brake distances is the friction coefficent of static and kinetic friction are different.

the static friction coefficent for rubber on dry/wet tarmac is about 0,8/0,5
and the kinetic friction coefficent for rubber on dry/wet tarmac is about 0,5/0,3
(taken from my "tafelwerk":smileypul)

simplyfied:
brakedistance ~ maximum brake force (applied to the tyre surface) * friction coefficent


You're on the right track generally, but your braking equation (well, proportionality) is nonsense. Braking distance is INVERSELY proportional to the deceleration of the vehicle (to be more precise, it's the square of the initial velocity divided by twice the deceleration, assuming constant decel). The deceleration is equal to the braking force divided by the car's mass. The braking force is equal to the friction coefficient multiplied by the WEIGHT on the tyre...
Also, your friction coeffs look somewhat too low; certainly the static one for dry tarmac (should be 1 or a little over 1).

So ABS was put on all four wheels and the end resault is a bunch of miss educated drivers that belive ABS is there to help them stop, which it is NOT.
I can't state this with enough force, ABS IS NOT TO HELP YOU STOP, IT HELPS YOU STEER!
Let's not get carried away here. Yup, ABS helps you steer (cos front wheels are useless for steering when tyres are locked). But it's bloody important that it helps you stop too. Have you ever had to slam down the brake pedal on a wet straight 2-lane road to avoid hitting the cars in front? (And oncoming traffic in other lane, so nowhere to swerve.) Done it in ABS and non-ABS cars? Noticed a scary difference in the braking distance? In my experience, it's bloody hard to avoid lock-up in the wet in real-life "oh shit" situations, especially at lowish speeds where the entire braking time might be only 2 or 3 seconds. Maybe if you practice cadence braking a LOT, you might stop a bit quicker, but bad cadence braking will stop you more slowly than locked wheels :).
In the not too distant past, the police used to look for skid marks to show that a driver did his/her best to stop! (Wonder what happened to any poor bugger that was excellent at cadence braking? :)) I guess they've mostly had to chuck the towel in, now that so many cars have ABS... Anyway, the point being, normal human beings slam the pedal to the floor in emergency situations. End of story. Yes, all four tyres will lock if no ABS. That doesn't make them dumbasses, it means they aren't racing drivers, and haven't had skidpan training (digressing a bit, I think it should be obligatory for all :)).
The drivers you mention are only mis-educated if they think ABS *only* helps them stop, rather than helps them stop AND helps them steer... I'd not complain about your statement if the difference in braking distance with ABS wasn't so dramatic - we're not talking "slightly shorter braking distance + ability to steer" here.

[Neilser]

Once you know the car well enough and used to such technique, threshold braking is possible. If you look at the WRs in LFS (especially the formulas') you can see that when they trailbrake, they release the brake progressively as they steer, to allow directionnal power and braking power to perform at the same time. The wheels are at the very verge of blocking, and I'd call that luck if it was on one corner, but not in every single one of the track ;)

Once you're used to the car and its behaviors on different kind of tracks, then I'm pretty positive you can threshold brake very often and be more efficient than an ABS system.
Hmm, how do you figure that a human with one brake pedal can optimise the braking force on four wheels? How do you figure that a computer couldn't be trained to do threshold braking, and a damn sight more effectively than a human? What data does the human have that the computer wouldn't have? (Apart from knowing where they want the car to be in a few seconds, which admittedly could make a difference now and then, but clever ESC systems probably do a damn good job of taking steering angle into account anyway.)
sgb27's reply should really have convinced you already :)

[DragonCommando]

Let's not get carried away here. Yup, ABS helps you steer (cos front wheels are useless for steering when tyres are locked). But it's bloody important that it helps you stop too. Have you ever had to slam down the brake pedal on a wet straight 2-lane road to avoid hitting the cars in front? (And oncoming traffic in other lane, so nowhere to swerve.) Done it in ABS and non-ABS cars? Noticed a scary difference in the braking distance? In my experience, it's bloody hard to avoid lock-up in the wet in real-life "oh shit" situations, especially at lowish speeds where the entire braking time might be only 2 or 3 seconds. Maybe if you practice cadence braking a LOT, you might stop a bit quicker, but bad cadence braking will stop you more slowly than locked wheels :).
In the not too distant past, the police used to look for skid marks to show that a driver did his/her best to stop! (Wonder what happened to any poor bugger that was excellent at cadence braking? :)) I guess they've mostly had to chuck the towel in, now that so many cars have ABS... Anyway, the point being, normal human beings slam the pedal to the floor in emergency situations. End of story. Yes, all four tyres will lock if no ABS. That doesn't make them dumbasses, it means they aren't racing drivers, and haven't had skidpan training (digressing a bit, I think it should be obligatory for all :)).
The drivers you mention are only mis-educated if they think ABS *only* helps them stop, rather than helps them stop AND helps them steer... I'd not complain about your statement if the difference in braking distance with ABS wasn't so dramatic - we're not talking "slightly shorter braking distance + ability to steer" here.


ABS was never intended to help you stop EVER. thats why it has a minimum activation speed, usualy this is around 15km/h.

In the situation you describe, I could get the vehicle to stop in a shorter distance without ABS, simply because ABS sucks donky balls in the rain. ABS stops you shorter in dry conditions but no one will ever convince me that it will stop shorter in the rain. I have experianced it in many vehicles all the way up to a BMW, NONE of them EVER stop faster with ABS in the rain. On dry pavement sure, but in the rain I'd much prefer to go without ABS.

If you want to argue that point, argue with my 1999 turbo diesel van when I ended up in a crosswalk because the ABS decided to kick in because of a puddle. The vehicle basicaly lost all brake power for just long enough that the front of the vehicle ended up in the middle of the crosswalk. I know for a fact that if the ABS hadn't kicked in the Van would have stopped right at the line. locked wheels or not.

[Trebuh]

Quote:"You're on the right track generally, but your braking equation (well, proportionality) is nonsense. Braking distance is INVERSELY proportional to the deceleration of the vehicle (to be more precise, it's the square of the initial velocity divided by twice the deceleration, assuming constant decel). The deceleration is equal to the braking force divided by the car's mass. The braking force is equal to the friction coefficient multiplied by the WEIGHT on the tyre...
Also, your friction coeffs look somewhat too low; certainly the static one for dry tarmac (should be 1 or a little over 1)."

well my thoughts are:

s=a/2*t²+ v0 * t (distance=acceleration / 2 multiplied with square of time + (starting)velocity * time)

deceleration = -a, a(friction) = a*friction coefficent

=> on dry tarmac you can apply more acceleration to a tyre than on wet tarmac, so a(friction) for wet must be below a(friction) for dry tarmac

the mass of the car is not relevant because the tarmac doesnt change your cars mass F=m*a => F~a
the mass is the mass of the car and its applied to all your tires (because you arent braking with only one tyre, and the more force is applied to your front wheels, the less force is applied to the rear ones. thats why the mass on the tyre surface is not relevant as well.

where do you find INVERSELY? couldnt find it anywhere
with a friction coeff above 1 you could build a perpetuum mobile because the [mechanical work] for acceleration would increase, and the conversation of energy was wrong

the lower (acceleration*friction) the longer the distance, so my friction coefficents are right!

[Neilser]

In the situation you describe, I could get the vehicle to stop in a shorter distance without ABS, simply because ABS sucks donky balls in the rain. ABS stops you shorter in dry conditions but no one will ever convince me that it will stop shorter in the rain. I have experianced it in many vehicles all the way up to a BMW, NONE of them EVER stop faster with ABS in the rain. On dry pavement sure, but in the rain I'd much prefer to go without ABS.

If you want to argue that point, argue with my 1999 turbo diesel van when I ended up in a crosswalk because the ABS decided to kick in because of a puddle. The vehicle basicaly lost all brake power for just long enough that the front of the vehicle ended up in the middle of the crosswalk. I know for a fact that if the ABS hadn't kicked in the Van would have stopped right at the line. locked wheels or not.

Hmm, everything I've ever seen about real-world testing of ABS (and that includes a lot of stuff I've re-read recently :)) says it's pretty decent in the dry (some systems being beaten by humans) and much better in the wet (very rarely beaten by humans). Do you have any refs supporting your view that it's better than humans in the dry but NOT the wet? One link (of many) supporting the opposite view is http://www.nhtsa.dot.gov/cars/rules/regrev/evaluate/808206.html
One more for good luck (look in the vicinity of page 36): http://books.google.co.uk/books?id=I511spiUbQsC&printsec=frontcover#PPA36,M1

And please, how can I argue with your feeling that you would have missed the cross-walk if only you hadn't had ABS? :)

To get back (cough!) to the original poster's topic (!) - it's a bit of a shame if the LFS ABS system is a "dumb" one which doesn't maintain directional stability. We could argue all day about whether the earliest/crappiest ABS systems invented would spin the car if one side was on ice (FWIW, I guess this is plausible), but it's irrelevant. Perhaps the devs will tweak it slightly, to make it less dumb?

[NightShift]

Perhaps the devs will tweak it slightly, to make it less dumb?

Who knows? Admittedly 0.6A was delayed to refine both the mechanical AND electronic simulation of the VWS, the ABS being too 'dumb' could as well be one of those areas which needed refining.

We'll find out out as soon as the new patch is released :shrug:

[Neilser]

well my thoughts are:

s=a/2*t²+ v0 * t (distance=acceleration / 2 multiplied with square of time + (starting)velocity * time)

This equation is correct. However, it's not the one you want. You don't care about braking TIME here, you just want to relate braking distance to initial velocity and acceleration.
The useful equation here is normally written as "v^2 = u^2 + 2 a s", which for our purposes is best rewritten as "s = -u^2/(2 a)" (since a is negative in this case, s is of course still positive). I suspect you have confused yourself with your own equation, and interpreted it to mean that "s ~ a"? The different assumption implicit in this equation breaks with your usage, if that's what you have done. (This is also where the "inversely" problem got created.)

deceleration = -a, a(friction) = a*friction coefficent

Don't know how to make sense of that. My best stab is that you meant one of those "a" values to mean gravity? If not I'm just lost...

=> on dry tarmac you can apply more acceleration to a tyre than on wet tarmac, so a(friction) for wet must be below a(friction) for dry tarmac

Hey, something we agree on :)

the mass of the car is not relevant because the tarmac doesnt change your cars mass F=m*a => F~a
the mass is the mass of the car and its applied to all your tires (because you arent braking with only one tyre, and the more force is applied to your front wheels, the less force is applied to the rear ones. thats why the mass on the tyre surface is not relevant as well.

Yup, you can ignore the mass of the car in many cases, since the weight of the car is just the mass of the car multiplied by gravity; you can't however ignore gravity, which I suspect you have forgotten about entirely (but I'm hoping you meant to include it, hence my comment above).

where do you find INVERSELY? couldnt find it anywhere

By inversely, I simply mean "s ~ 1/a". As in "s = v^2/(2a)" or some variant on that.
with a friction coeff above 1 you could build a perpetuum mobile because the [mechanical work] for acceleration would increase, and the conversation of energy was wrong

Eh, no :) Friction coefficients above 1 have NO special meaning. It simply means, for example, that the lateral force required to push an object along becomes greater than the force with which the object is being pressed ONTO the surface. So if you tilt a table with an object on it whose friction coeff relative to the table is 1, the angle you have to tilt the table at to create slip is 45 degrees. Bigger than 1 means the tilt angle exceeds 45 degrees. Less than 1... well you get the idea.

the lower (acceleration*friction) the longer the distance, so my friction coefficents are right!
Dunno what your picture says (don't speak German) but your figures don't agree with what I've seen. However, tyre compounds vary a lot, and 0.8 isn't so far away from 1 that we should be fighting about it (I'm not seeking to make a big deal of this particular point :)) But, as it goes, I'm horrified by the numbers you've quoted, and am intrigued to know which tyres and which tests are implied here (designed for endurance but crap grip?).

It might also interest you to know that the tyre model in LFS uses a friction coeff of somewhere near unity for ROAD_NORMAL tyres...
Well, sort-of. It's more complex than that, and in fact friction coefficients are not generally independent of the force between the surfaces (which is what we get told in school). LFS actually models reality in quite a lot more detail than simply something like "frictional force = mu * weight". This is a big part of why the tyre camber matters, for example. Then there is adhesion ("stickiness") to account for, which is another thing entirely. If I say much more than this though, I'll be at risk of talking crap myself :)

[Neilser]

Who knows? Admittedly 0.6A was delayed to refine both the mechanical AND electronic simulation of the VWS, the ABS being too 'dumb' could as well be one of those areas which needed refining.

Good point. Hopefully you've hit the nail on the head there ;)

[DragonCommando]

honestly I think personal experiance trumps some stupid tests. of course they are going to say ABS is just as good in the rain, otherwhise people would think ABS isn't such a good idea.

I know from personal experiance that ABS doesn't perform as well in the rain, and it gets even worse on snow too. In the rain I CAN stop shorter than an ABS system, I have done it. In a Mercedes no less. But as I said, thats not the point of ABS, ABS is to allow you to steer while you brake.

If ABS was intended to help you stop, then it would say so in all of my auto mechanic books right? Well it doesn't, it states that ABS is NOT intended to help a car come to a stop, it is intended to help the driver steer in a panic situation where they would normaly lock the wheels and slide into the obstruction regardless of steering inputs.

Theres even a technique that helps you avoid an accident without ABS.
But they don't teach it anymore because people are too lazy, they let the car take care of them, instead of the other way around.

[DrBen]

I cannot believe it. People just should dare to read some (put a random number of 10<x<100 here) pages BACKWARDS sometimes. That would save some really helpful and man-friendly characters a lot of valuable time on this board. Really is there anything worth-while that hasn't been answered in the last 2 months or so of "ABS" and "ABS in reverse" spin-off threads??

Just re-read and try to understand what this man is telling you:
honestly I think personal experiance trumps some stupid tests. of course they are going to say ABS is just as good in the rain, otherwhise people would think ABS isn't such a good idea.

I know from personal experiance that ABS doesn't perform as well in the rain, and it gets even worse on snow too. In the rain I CAN stop shorter than an ABS system, I have done it. In a Mercedes no less. But as I said, thats not the point of ABS, ABS is to allow you to steer while you brake.

Yes, everything this man says is right - as long as you refrain from giving him a load of a hard time, already!
I drive an (old-ish) Mercedes (a 2.2l W124, or maybe better-known as the re-named first "E-Klasse" from 1994, last face-lift and last year of production with water-based paint -- that was already re-done by some more decent coulour).
And what a coincidence we did have some snow recently -- and sure enough the ABS started to kick in VERY EARLY, indeed!
It made putting the tyres to full use impossible in terms of transmitted braking-force, but it would not let me make a fool of myself by braking backwords into th pearly gates.
So yes, the first generation of ABS implementations were just that: a heck of a really usefull improvement that looks a bit "unfinished" when judging by the means of today's standards.

Theres even a technique that helps you avoid an accident without ABS.
But they don't teach it anymore because people are too lazy, they let the car take care of them, instead of the other way around.Yeah, they do not teach it any more, here as well. BUT it still gets mentioned in th theoretical practice material. It's just that noone in his right mind would unplug the fuse of the ABS-system on a modern car knowing that the manufacturer didn't get the state's approval to be "road-legal" for the deliberate action of disabling a car's much-desired security-function. Even insurance-issues might arise when acting this stupid. Moreso for driving schools!
It also saved my neck a few times when driving a car at work in my early days. AND NO I didn't get to practice that beforehand, I just remembered and just DID it -- and it proved to help me keep the balance and actually brake to a full halt before crashing into some idiot's expensive car that that man just stopped without reason in right after an icy bit of road that had to do with some water-leaquage around that area that nobody would have imagined to find there.
I then felt quite lucky, to say the least.

Of course modern (=todays) cars do fancy hugely improved stability helps and whistles that will not show any of the disadvantages of the early ABS systems in use on older cars. They are simple "fire and forget"-missiles roaming the roads that will handle just about anything dangerous for you -- as long as you don't point your wheel right into a tree.

Cheers
DrBen

[Trebuh]

well we cant discuss the dependence on tyre compounds or camber angle because i think noone out of us is an engeneer so we have to think as simple as possible and i didnt know the formula v² = u² + 2as and it confused me. But its still the same, but it just proves my point, i think.

s~1/a

ok thats right and means if a increases, the distance decreases, dependent on starting velocity, right?

µ is the friction coefficent and µ is lower for sliding than for "gripping" (0,5 / 0,8)

we can only think of braking on an horizontal plain road without wind because it would become too complicated and there the weight of the car doesnt influence the braking distance.

for the same car with the same tyres on straight direction: s=-u²/(a*µ)
the brake force: F = m*a and the friction force F = m * a * µ
so a(brake) = (m * a * µ) / m

example:
m = 1 ton
a = -25 m/s² (negative because we are braking) EDIT: 25 is alittle high, isnt it? there is a mistake
u = 100 km/h

1.) dry tarmac static friction:

s=-(27m/s)² / (1ton * -25m/s²* 0,8) / 1ton

s = 36,45m

2.)dry tarmac kinematic friction:

s=-(27m/s)² / (1ton * -25m/s²* 0,5) / 1ton

s = 58,32m

your formula did very well, but i think the friction coefficents are hardly right (the difference is too high) 0,8 and 0,7 would be better.

But i think its hard to say from experiance whats faster slow, because with abs time feels much more longer (my exp.) but on savety training we could prove that abs is much better braking even under steering and without. But you cant compare braking without abs(straight) and withabs under steering (there you need alot of forec for steering)

AND: i talked about that topic with a physicist and he was my opinion so i cant be that wrong and measured and expearianced values can differ (a little)

the technical solution might differ because of materials and the distance should differ in real life, of course. But braking distance by locking the wheels is more or equal than with abs on straight

EDIT: i made a mistake when i tried to implement µ to the equation. yes its g not a and its the maximum appliable force to the tyres and µ is different for every pair of surface/tyre

[Neilser]

honestly I think personal experiance trumps some stupid tests. of course they are going to say ABS is just as good in the rain, otherwhise people would think ABS isn't such a good idea.


Hell yes, controlled tests are so worthless compared to subjective assessments ;)
But seriously, if seeing test results doesn't convince you, I give up on convincing you... :shrug:
Perhaps the info will be useful to other readers of the thread tho.

One remark about what they say about ABS though - in lots of places you will see vague warnings along the lines of "ABS isn't meant to help you stop faster", and they go on to warn about snow, gravel etc. (where locked tyres actually help, and ABS is universally acknowledged to increase braking distance).
MY interpretation of these statements is different to yours though: I think they are simply worried that people will assume they can stop MUCH faster with ABS, and will crash when they turn out to be wrong. So... they downplay the braking-distance benefits of ABS.

[Neilser]

for the same car with the same tyres on straight direction: s=-u²/(a*µ)
the brake force: F = m*a and the friction force F = m * a * µ
so a(brake) = (m * a * µ) / m

You're very close to getting it right now, but you still haven't got to grips (no pun intended :)) with gravity. Gravity is the acceleration pushing the car into the road (about 9.8m/s²) and it's gravity (not the deceleration of the vehicle) that you must multiply by the friction coefficient to estimate the car's maximum possible deceleration.

You could ask your physicist friend to explain this bit.

But here's a quick sample calculation, using your values where applicable.

Dry tarmac, static friction case, u=100km/h (thus about 28m/s).
s=u²/(2a) (I'm conveniently ignoring minus-signs :))
max value of a = g*µ = 9.8*0.8 = 7.84m/s²
(Note - I have indeed ignored the car's mass in this equation.)
Thus s = 28²/(2*7.84) = 50m

Please make me happy and tell me that this helped you ;)
(NB: the final value is close to yours, but you dropped a factor of two in the denominator, and then invented (how??) a massive deceleration of 25m/s² to claw it back :))

the technical solution might differ because of materials and the distance should differ in real life, of course. But braking distance by locking the wheels is more or equal than with abs on straight
Yes, true for tarmac. But most of the disagreements here seem to be about whether humans can pulse the brake pedal better than ABS computers :)

[Trebuh]

Sorry, i think i have to go a bit deeper into theory...:shrug:

but the warnings are in my opinion for those people that think abs is like magic.

i dont know how to get the µ into the equation

EDIT:
another formula to base on:

Ekin = Wfr (Kinetic Energy = Friction Work)

m/2*v² = m * g * µ * s

s = v²/2gµ

that means braking minimal possible distance only depends on velocity and µ

so i think WE are right now.. hehe i should prepare better for my exams

[DragonCommando]

Hell yes, controlled tests are so worthless compared to subjective assessments ;)


Thats exactly the problem here, they are controlled tests, they still go for the ideal conditons or the worst possible conditions. They don't account for every conditon or environment. Doing something on a test track or in a lab is alot different than doing it in a real life situation.

People assume just because it works in the tests its going to work just as well in the real world. That kind of thinking is what leads to serious problems on the road.

Now something for everyone to read.

The technique I mentioned earlier for avoiding obstructions in the road in a car without ABS.
I was never told what this technique was called, I was just told how to do it. I call it "lock and pop steering"

Lets start with the situation, you are driving down the road and something comes up infront of you, a car stops or a kid falls off his bike, anything.

Your car doesn't have ABS, and there isn't space to stop. If you are a good driver you will have already located a way out of the situation, sometimes even before the situation presents itself.

-The first thing you do is lock the brakes. Yes, I'm serious. Lock em up hard.
-while the car is sliding forward you turn the steeringwheel in the direction of your way out.
-Pop off the brakes and the cars nose will shoot out in the direction of said way out.
-Steer and re-apply a generous amount of brake force.

This should all happen VERY quickly, right up to the part about steering and braking, you do not want to rush that last part as its very important in maintaining controll.

This is for lower speed situations, but it can be done on the highway as long as you are on an outside lane and there is room on the shoulder. When done on the highway it's advisable to skid as long as possible, this way you bleed as much speed as possible before poping out onto the shoulder.

[S14 DRIFT]

It's very well giving us your "lock your wheels and magically steer out of the way" method there, however you try doing that when your front bumper is 10ft away from some kid and you're going at 25mph.

A good driver would have seen the hazard ahead (kid on bike in the middle of the road, only going to go badly anyway, or the car or whatever) and either slowed down completely.

I'd rather apply steer and brake at 80%, rather than brake at 100%, release, then steer, especially when someone else's life is in the balance of your ability to not panic.

[legoflamb]

Lets start with the situation, you are driving down the road and something comes up infront of you, a car stops or a kid falls off his bike, anything.

Your car doesn't have ABS, and there isn't space to stop. If you are a good driver you will have already located a way out of the situation, sometimes even before the situation presents itself.

-The first thing you do is lock the brakes. Yes, I'm serious. Lock em up hard.
-while the car is sliding forward you turn the steeringwheel in the direction of your way out.
-Pop off the brakes and the cars nose will shoot out in the direction of said way out.
-Steer and re-apply a generous amount of brake force.

This should all happen VERY quickly, right up to the part about steering and braking, you do not want to rush that last part as its very important in maintaining controll.

This is for lower speed situations, but it can be done on the highway as long as you are on an outside lane and there is room on the shoulder. When done on the highway it's advisable to skid as long as possible, this way you bleed as much speed as possible before poping out onto the shoulder.

Previously, I wanted to avoid joining the discussion, however, in the event that someone might think this "lock and pop" technique is not a last resort, I felt obligated to explain.

Not that the "lock and pop" technique is not viable, but it would not be the optimal one.

That technique would actually limit the possibilities available to maneuver the vehicle out of the projected path and into a desired path. First, the coefficient of friction provides higher grip levels than the skid friction of any tire. Stopping distances would become greater while sliding. Sliding is most often not optimal for slowing to a stop. Also, applying the breaks while the car has rotational momentum would induce more rotation. Finally, like you said the conditions are never the same, should the road be extremely wet or icy, the car would be put into a sideways slide or spin where no amount of ABS would help. This would make only one outcome available, and that is where ever the car is going to slide.

FYI: You can lock up with current ABS systems. The sensors have to update the computer to every change such as pressure changes on the brake-pads caused by the driver,.. etc., which are unpredictable causing a back and forth switch between locked and not locked.

On a side note, on ice, that "pop and lock" technique is not very efficient in rotating a car.

Therefor, inducing slide by quick rotation means that in a particular situation contact is unavoidable, and the driver wants to avoid a front end collision. This risks injury for the driver or passengers (if any) because the sides have less crumple zone to lengthen the impulse of the collision. By the way, unavoidable contact is always a last resort for those who want to avoid contact.

I will not offer a counter avoidance technique because there are no definable parameters to base a decision off of.

Definable Parameters: ie. distance, vehicle stopping distance, obstruction (pedestrian, wall, vehicle, animal, furniture, road conditions,... etc.)

And there is no "first thing to do" because the situations change just as the conditions change.

Also, in the heat of the moment, actions are rarely thought through.

I don't care to link the sources for the fact that maintaining but not exceeding the coefficient of friction provides better stopping power and control ability.

Edit:

http://www.physics.sc.edu/~rjones/phys101/tirefriction.html

http://hal.archives-ouvertes.fr/docs/00/05/14/75/PDF/vsd05.pdf

[senn]

NO U

sorry had to be done.

And i have always been taught to Pulse brake, or modulate, when emergency stopping, to maintain control of the vehicle. Practiced it, and utilized it (generally due to my other poor driving habits, ie following too closely)

It works. But you still have to be vigilant on other escape routes, traffic around you etc. I have never owned a car with ABS, but have always upgraded brake fluid and pads for better feel/less fade, and the last couple of cars i've owned, tyres too, for SLIGHTLY better stopping distance. Sliding is crap, takes forever to stop.

[DragonCommando]

It's very well giving us your "lock your wheels and magically steer out of the way" method there, however you try doing that when your front bumper is 10ft away from some kid and you're going at 25mph.

A good driver would have seen the hazard ahead (kid on bike in the middle of the road, only going to go badly anyway, or the car or whatever) and either slowed down completely.

I'd rather apply steer and brake at 80%, rather than brake at 100%, release, then steer, especially when someone else's life is in the balance of your ability to not panic.


Like I said, a good driver will have already considered the hazards and been looking for a way out.

If you think this method isn't realy a good idea, I suggest you look at an old driving technique book. That, along with a driving teacher, is where I learned that technique.

Also, way to discredit your veiw, 10ft away? what are you crazy?
If you EVER need to avoid something you should have already been ready to avoid it. at 10ft you should already be going slow enough to come to a complete stop if that kid infront of you falls off his bike.

This is a REAL steering technique, and if you read it properly, your wheels arn't locked when you actualy avoid the obstruction.
The reason you actualy brake before steering and poping off the brakes it to load your front tires, then when you pop off the brakes your wheels are doing nothing but STEERING. This allows you to get the full steering capability from your tires just for that instant you need it to steer away. Then you re-apply brakes WITHOUT locking them.

Ask ANY pro driving instructer, they will tell you exactly the same.

The only place I've seen this method mentioned recently is on a show called Canada's worst driver, but EVERYONE should know how to do it.

In the event that there is no where to go, then you have to consider braking as hard as possible without locking, and if it's another car infront of you, hit as square as possible, maximize the use of the front and rear of the cars. Personaly, I belive there is always something you can do, or could have done to prevent this situation.

[freddyalek90]

Like I said, a good driver will have already considered the hazards and been looking for a way out.

If you think this method isn't realy a good idea, I suggest you look at an old driving technique book. That, along with a driving teacher, is where I learned that technique.

Also, way to discredit your veiw, 10ft away? what are you crazy?
If you EVER need to avoid something you should have already been ready to avoid it. at 10ft you should already be going slow enough to come to a complete stop if that kid infront of you falls off his bike.

This is a REAL steering technique, and if you read it properly, your wheels arn't locked when you actualy avoid the obstruction.
The reason you actualy brake before steering and poping off the brakes it to load your front tires, then when you pop off the brakes your wheels are doing nothing but STEERING. This allows you to get the full steering capability from your tires just for that instant you need it to steer away. Then you re-apply brakes.

Ask ANY pro driving instructer, they will tell you exactly the same.

The only place I've seen this method mentioned recently is on a show called Canada's worst driver, but EVERYONE should know how to do it.

I really can't understand how on earth "locking-don't brake and steer-brake again" could be better than "brake AND steer in the same time w/o locking", but if you're convinced we can't do anything.
When you say that ABS will increase your stopping distance even in the rain, I disagree (talking of most drivers), but talking about skilled drivers, you could have a point.
But saying that "lock and pop" is better than ABS, sorry... You make me wonder... Have you ever tried a modern car with a modern ABS?

Of course, ABS isn't witchcraft, it can't do magical stuff to stop you. But it makes you stop BETTER, even if not faster (but I doubt this).
ABS saved me and my family from a crash the first time we drove our new car, in '99. We had ABS, the other car didn't, we stopped far enough to avoid touches, but it was really a centimeter away. And that was a straight-line stop. Then I avoided to rear-end a car in a traffic jam by steering around it, without time to do this "lock&pop" technique.

[DragonCommando]

I really can't understand how on earth "locking-don't brake and steer-brake again" could be better than "brake AND steer in the same time w/o locking", but if you're convinced we can't do anything.
When you say that ABS will increase your stopping distance even in the rain, I disagree (talking of most drivers), but talking about skilled drivers, you could have a point.
But saying that "lock and pop" is better than ABS, sorry... You make me wonder... Have you ever tried a modern car with a modern ABS?

Of course, ABS isn't witchcraft, it can't do magical stuff to stop you. But it makes you stop BETTER, even if not faster (but I doubt this).
ABS saved me and my family from a crash the first time we drove our new car, in '99. We had ABS, the other car didn't, we stopped far enough to avoid touches, but it was really a centimeter away. And that was a straight-line stop. Then I avoided to rear-end a car in a traffic jam by steering around it, without time to do this "lock&pop" technique.


please, please, PLEASE qoute me saying lock and pop is better than ABS.

I never said lock and pop is better, I said lock and pop is a good way to do it if you DON'T HAVE ABS.

The physics should explain why it's better.

Your tires only provide so much grip, and when you brake and steer at the same time you are splitting that grip into two uses, when you lock and pop your tires are ONLY providing steering for that split second you use them to point the nose of the car away, then you can use the brakes again. Otherwhise you can't steer as quickly and might still understeer into the side of the obstruction.

You'd be surprized how well this works if you tried it. I HAVE tried both, avoiding a crash in a car with ABS and doing the same in a car without, and you'd be surprized how quickly you can actualy do this technique. Your tires only realy have to be locked for the split second it takes to turn the steering wheel and load the front tires.

lastly, I think you missunderstood what I wrote. You don't lock the brakes then steer, you lock the brakes and steer the same time, then pop off the brakes and re-apply them.

[freddyalek90]

[snip]
Ok, I admit, I misread what you posted.
What I meant to say was that having ABS is just better; Maybe you can't stop faster on dry road, but on wet I bet you could stop twice as fast with anti-lock brakes. And on snow/ice/gravel maybe you stop in more space, but the car is still controllable. I prefer to stop in 20ft more but avoid the crash then stop in 20ft less but still crash the car. :D
For me, having an electronic friend and knowing that it is there to help you when you need it is just better.

The difference is that without ABS you have to learn a technique not to skid and crash under heavy braking (lock/pop, or cadence brake, or threshold brake), with ABS it all comes really naturally. Brake hard and keep pressed, steer, avoid, stop braking.

And, last but not least, I know well the "lock & pop" technique, I have done it quite a few time driving a car w/o ABS. I was just simplifying 'cause I was using my mobile, and here it was 7 o' clock in the morning, so I was fast asleep :D.

[S14 DRIFT]

Like I said, a good driver will have already considered the hazards and been looking for a way out.

If you think this method isn't realy a good idea, I suggest you look at an old driving technique book. That, along with a driving teacher, is where I learned that technique.

Also, way to discredit your veiw, 10ft away? what are you crazy?
If you EVER need to avoid something you should have already been ready to avoid it. at 10ft you should already be going slow enough to come to a complete stop if that kid infront of you falls off his bike.

This is a REAL steering technique, and if you read it properly, your wheels arn't locked when you actualy avoid the obstruction.
The reason you actualy brake before steering and poping off the brakes it to load your front tires, then when you pop off the brakes your wheels are doing nothing but STEERING. This allows you to get the full steering capability from your tires just for that instant you need it to steer away. Then you re-apply brakes WITHOUT locking them.

Ask ANY pro driving instructer, they will tell you exactly the same.

The only place I've seen this method mentioned recently is on a show called Canada's worst driver, but EVERYONE should know how to do it.

In the event that there is no where to go, then you have to consider braking as hard as possible without locking, and if it's another car infront of you, hit as square as possible, maximize the use of the front and rear of the cars. Personaly, I belive there is always something you can do, or could have done to prevent this situation.

Please don't take everything I say as literal matter of fact, because it's not. And you know it.

And frankly, you can say what you like but I'd prefer to brake whilst steering, remaining in full control 100% of the time. But if it's a risk you're willing to take. As I said, if you could do that then fair play. But I'd rather not.

Key point I'm making is that you are not in control ALL THE TIME. The moment you lock up, you are no longer under full control, even if it's part of a plan of control, if you see what I mean.

The fact it's mentioned on Canadas worst driver sums it up, really! :D

Besides, if it's a kid or another car, it's not like you need to move 25ft out of the way, most cars are less than 6ft wide and even most bicycles with child lying on the floor are under 4 or 5ft across. :)

Hope you don't take everything I say literally. :)

[DragonCommando]

@S14
I'm trying to be friendly, I hope I'm not offending you or anyone. Its just realy hard to emphasize some points without sounding rude.

Anyway, the reason that it's on canada's worst driver is because they where trying to teach those people how to drive safely, although not all the information on the show is correct, that part is.

The problem with this technique is that it goes against instinct, people want to stop as quickly as possible when avoiding a collision, but this technique says to release the brakes, and that makes alot of people nervous. Which is understandable.

But, if you lock up your tires intentionaly, you are still technicaly in control, your car may not steer when you turn the wheel, but it will steer as soon as you let go of the brakes, and it will steer fast(er). I resisted this technique at first too, right up until my dad (very oldschool) practiacly forced me do it, afterward I was blown away at how quickly it can get the car's nose pointed in another direction.

I've tested this in LFS actualy, and it works almost the same as it does in real life. I found that I actualy cleared the cones and the stopped car (hay bales) with more space on either side than I did when I tried it with ABS, the ABS seemed to make the steering slower. However, the car stopped shorter after with ABS than it did without.

The problem with threshold braking in this case is that the farther you turn the wheel the lower that threshold is. The more you turn, the less you brake. So they teach you to split it up, so your tires are only doing one thing at a time.

[legoflamb]

The problem with the technique is that the people teaching it assume that the drivers is/was going to lock up anyway. As a matter of fact you can load the front end more while not sliding the front because as the tire starts to slip they provide less frictional force. More force means more front tire load.

What I'm trying to say is the technique would work better if, while braking in a straight line, you didn't lock up and then turned the wheel and applied the brakes like you said.

[Papa]

Sorry, i think i have to go a bit deeper into theory...:shrug:

but the warnings are in my opinion for those people that think abs is like magic.

i dont know how to get the µ into the equation

EDIT:
another formula to base on:

Ekin = Wfr (Kinetic Energy = Friction Work)

m/2*v² = m * g * µ * s

s = v²/2gµ

that means braking minimal possible distance only depends on velocity and µ

so i think WE are right now.. hehe i should prepare better for my exams


Hey Trebuh,

you are ignoring that your µ doesn't have a constant value. It depends on slip. (Typical slip ratio for maximum µ is about 3 - 15 % depending on tire.)

It's not like you just HAVE 0.8 of µ (or 1.0 or 1.2 or whatelse) while driving down the road. Rather regard it as the maximum friction coefficient your tire can possibly reach in this very driving/track condition. As sgb27 stated, reaching the maximum µ is a very unstable situation.

Furthermore the maximum µ a tire can reach is depending on tire load. This is why your car's mass (in combination with position of center of gravity and deceleration) has great effect on how much brake force you can generate.

If you could measure "live" µ, what actually automotive engineers try to do (or at least try to simulate/predict), then you would notice that it is a very, very VERY dynamic parameter.

All this said w/o even considering the track conditions being inconstant as well.

While people are achieving more realistic µ measurement/simulation methods, ABS are getting better and coming closer to being able to actually brake with maximum µ. As long as they don't, it is possible that very experienced and skilled drivers are able to "outbrake" an ABS. If an ABS is badly applied it is possible that braking with locked brakes would even lead to a shorter brake distance.

Regards,
Papa

[S14 DRIFT]

@S14
I'm trying to be friendly, I hope I'm not offending you or anyone. Its just realy hard to emphasize some points without sounding rude.

-snip-

:nod: 'tis all good! :D

[hagenisse]

All the skilled driver talk seems to be based around old abs-systems. There is no way, no matter how skilled you are - that you are going to outbrake a modern system that can regulate each wheel individualy way faster than any human - using one pedal. Forget it.

Race drivers seems to understand this, since if its allowed, abs is used.

[Papa]

All the skilled driver talk seems to be based around old abs-systems. There is no way, no matter how skilled you are - that you are going to outbrake a modern system that can regulate each wheel individualy way faster than any human - using one pedal. Forget it.

Race drivers seems to understand this, since if its allowed, abs is used.

Agree.

I am only saying that it is possible that a skilled driver might be able to stop quicker w/o ABS than with badly applied ABS, which exist. Something some of the forum users even might have experienced with their 199x-whatsoever-model with ABS.

This of course is no evidence for skilled humans being better "brakers" than a modern ABS. As being "modern" needn't to be the same as "well applied" in any case.

[Trebuh]

you are ignoring that your µ doesn't have a constant value. It depends on slip. (Typical slip ratio for maximum µ is about 3 - 15 % depending on tire.)
[...]
If you could measure "live" µ, what actually automotive engineers try to do (or at least try to simulate/predict), then you would notice that it is a very, very VERY dynamic parameter.

All this said w/o even considering the track conditions being inconstant as well.

While people are achieving more realistic µ measurement/simulation methods, ABS are getting better and coming closer to being able to actually brake with maximum µ. As long as they don't, it is possible that very experienced and skilled drivers are able to "outbrake" an ABS. If an ABS is badly applied it is possible that braking with locked brakes would even lead to a shorter brake distance.

Regards,
Papa

I didnt ignore that µ isnt constant. I tried to prove that braking with ABS might (its a bad word for a provement) /should be better in case of brake distance than 4-wheel sliding.

The load on/at the tire isnt important, because the more load on the front wheels the less load on the rear wheels. The absolute load is both (only dependent on the cars mass)

i believe that the values from my "tafelwerk" are average values to calculate simple problems at school, but i experienced with my 10year old japanese ABS that's much better even than front-wheel-lock-braking.

While a savety training i participated those with ABS had massive advantages in brake distance to those without ABS. Some of those without ABS were sliding off the test area, while some of those with ABS (me included) hardly hit the cones.

I wanted to compare gripping and sliding while braking, but i wasnt able to prove / show my thoughts because of my lack of english and i took the wrong formula.

And before i got my ABS-car i had the same without, so i can say that i experianced the difference - for me as a non-professionnel driver. I wanted to explain that physically (the base of physical explanation is to simplify a problem) because som guys here are always arguing against ABS (with stupid conditions like gravel or ice)

[Papa]

I agree with your argumentation why braking with ABS SHOULD result in a shorter brake distance than w/o. Just wanted to point out why in some cases this might not be the case. Your argumentation works for perfect (!) ABS. Real ABS just can't keep µ at the very maximum "static friction level". And that µ depends on tire load is one reason for this.

I just quoted you not well at all I guess. Sorry for the misunderstanding.

Regards,
Papa

[Trebuh]

I think misunderstanding is an improtant matter if a lot of people from different countries try to discuss something... in foreign language

[DragonCommando]

The problem with the technique is that the people teaching it assume that the drivers is/was going to lock up anyway. As a matter of fact you can load the front end more while not sliding the front because as the tire starts to slip they provide less frictional force. More force means more front tire load.

What I'm trying to say is the technique would work better if, while braking in a straight line, you didn't lock up and then turned the wheel and applied the brakes like you said.


I will have to dissagree with the part about not locking loading them more, when you step on the brakes to threshold brake, you bring the weight onto the front wheels of the car, but once you pass it the weight is already transfered to the front wheels. So if you lock, you just happen to be passing the threshold and have already transfered the weight of the car.

What the locking does is allows you to turn the wheels without the car turning, this lets you set the exit angle in that instant you are sliding, and as soon as you release the brakes the car is going to dart out in that direction. If you threshold brake and turn the wheel at the same time it isn't going to react as quickly, even if you release the brakes while turning, you haven't set the exit angle before it happens, so the car is going to be sluggish about rotating. The reason the car darts out is because you are suddenly applying a force instead of gradualy.

[legoflamb]

I will have to dissagree with the part about not locking loading them more, when you step on the brakes to threshold brake, you bring the weight onto the front wheels of the car, but once you pass it the weight is already transfered to the front wheels. So if you lock, you just happen to be passing the threshold and have already transfered the weight of the car.

What the locking does is allows you to turn the wheels without the car turning, this lets you set the exit angle in that instant you are sliding, and as soon as you release the brakes the car is going to dart out in that direction. If you threshold brake and turn the wheel at the same time it isn't going to react as quickly, even if you release the brakes while turning, you haven't set the exit angle before it happens, so the car is going to be sluggish about rotating. The reason the car darts out is because you are suddenly applying a force instead of gradualy.

When you lock up the tires they supply less stopping force. That is why braking distances become longer when the tires lock up.

I do agree with the part about the sudden angular force on the front tires after the steering has been applied while locked up, but it's effective only if the suspension is soft and the chassis is riding a bit high.

However, if you were going to dart out to either side that would mean the sides are clear. In that situation where evasive action must be made, you could not brake altogether and just steer out of the way.

Like I said in my first post on this subject, that technique would not be the optimal one.

someone should probably move these post as they are not all that related to ABS in live for speed.

[rancid]

Last summer I was messing around with a Wiimote and was using it as an accelerometer in the car.

We did a test run with my friend's newly purchased Subaru Forester XT and the usefulness of ABS came up in the conversation - so we tested it of course. Braking from 80km/h to a full stop, on dry asphalt (about 20-25 degrees C):
-ABS produced a maximum of 1G longitudinal force
-threshold braking produced a maximum of about 1.1G longitudinal force
-braking distance was roughly the same (without pulling out the measuring tape)

If we get a chance, we'll try and do the same experiment on snow and ice, but don't hold your breath...

What I know is that I got to drive his aunt's '06 Subaru Legacy on snow and while handling was simply incredible, braking distance to a stop was pathetically exaggerated once the ABS kicked in.
Same thing with his cousin's '96 A4, once the ABS kicks in on snow or ice, you know you aren't stopping where you were initially planning...

[Byku]

Guys, got one question. Burning rear tires while holding the brakes, so that front wheels will be locked but rear will spin. I've seen a couple of movies on YT(like Mustang doing burnouts). In LFS it is impossible with abs on, so that means that those cars on YT has ABS disabled? That seems rational, but is it true?

[ACCAkut]

hmm, in a modern car there are several sensors and computers that react on your driving state, like g-force sensors, which won't be affected if the cars is standing still. That may be the reason

[e2mustang]

ABS and Traction control is different,for burnouts you have to disable the traction control,thats all in short :)

[Whiskey]

That seems that in LFS that works like an ESP system and not a symple ABS, isn't it?

[senn]

nope the ABS in LFS works like ABS. it won't stop you going sideways, won't stop it if u "pendulum" the car into a slide, it will just stop the wheels from locking (altho i did notice on the FZ5, ABS works when you brake + compression lock (ie stops wheels locking by releasing the brakes), which is handy :P)

But it's still only ABS, stopping the wheels from locking.

[S14 DRIFT]

Last summer I was messing around with a Wiimote and was using it as an accelerometer in the car.

We did a test run with my friend's newly purchased Subaru Forester XT and the usefulness of ABS came up in the conversation - so we tested it of course. Braking from 80km/h to a full stop, on dry asphalt (about 20-25 degrees C):
-ABS produced a maximum of 1G longitudinal force
-threshold braking produced a maximum of about 1.1G longitudinal force
-braking distance was roughly the same (without pulling out the measuring tape)

If we get a chance, we'll try and do the same experiment on snow and ice, but don't hold your breath...

What I know is that I got to drive his aunt's '06 Subaru Legacy on snow and while handling was simply incredible, braking distance to a stop was pathetically exaggerated once the ABS kicked in.
Same thing with his cousin's '96 A4, once the ABS kicks in on snow or ice, you know you aren't stopping where you were initially planning...

Bear in mind some cars ABS is 'better' than others, IE it allows more slip and thus better optimum braking, such as in many BMW's :)

[Whiskey]

Guys, got one question. Burning rear tires while holding the brakes, so that front wheels will be locked but rear will spin. I've seen a couple of movies on YT(like Mustang doing burnouts). In LFS it is impossible with abs on, so that means that those cars on YT has ABS disabled? That seems rational, but is it true?

That seems that in LFS that works like an ESP system and not a symple ABS, isn't it?

I know perfectly how ABS and ESP works. But I think that in this case it works like the ESP instead the ABS only

[Neilser]

I know perfectly how ABS and ESP works. But I think that in this case it works like the ESP instead the ABS only
But if you brake with one side of the car on grass, the LFS ABS system will spin you. Not what an ESP system would do I suspect...

[hazaky]

ABS and Traction control is different,for burnouts you have to disable the traction control,thats all in short :)
But, is that real ... when i drive a FZ5 and slowly take a drift angle. It keeps spinning well fast that it could make my car lose control :tilt:

[Whiskey]

But if you brake with one side of the car on grass, the LFS ABS system will spin you. Not what an ESP system would do I suspect...

And where I did say anything like that? :really:

I was talking about a burnout, I don't see the link to your point :shrug:

[Neilser]

And where I did say anything like that? :really:

I was talking about a burnout, I don't see the link to your point :shrug:
Chill - I didn't make any claim about what you said.
But what you did suggest was that the LFS ABS system was behaving like an ESP (in this instance), and I'm simply pointing out that it does not in general behave remotely like an ESP system where it matters (i.e. when the car is moving :))...
I don't have ESP myself (on my car, as against my brain :)) so I don't know how it behaves in odd situations like burnouts, but do you think it will produce this behaviour? Perhaps you have experience of it doing so on a real vehicle?

I just tried to get LFS to allow me to do a burnout with ABS on (like the poster of a few days ago). It worked but only in reverse where the ABS isn't active anyway :)
This is kind of weird, cos AFAIK real ABS systems don't activate at zero speed, and also because the LFS ABS system does noticeably allow the wheels to lock as your speed drops close to zero, which makes it seem like it deactivates below a certain speed (just like real systems, AFAIK). Oh well. What we need is a key to toggle the ABS status just like TC.

[e2mustang]

But, is that real ... when i drive a FZ5 and slowly take a drift angle. It keeps spinning well fast that it could make my car lose control :tilt:
If traction control is completle off sure u can spin out. I work with bmw and benz and in bmw the DSC sytem is 2 stages,first u push tha dsc button,but it wont take the traction off completly,but when u hold the button for a few sec,2 lights comes up,thats when its completly off.And this abs esp system,for example the old bmws dont have traction but they all have abs,so they can do burnouts too.:)

[S14 DRIFT]

Oh well. What we need is a key to toggle the ABS status just like TC.

I will +1 too that, however I'm sure many die-hard LFS users will say that since only a small handful of cars have switchable ABS, aside from removing a fuse, that it's not realistic!! :really::shrug:

[Whiskey]

ABS don't allow (or try to not allow) the tyres to block.

The ESP keep the speed of every wheel as close as posible.



So in a burnout the ABS should not do anything

[evilgeek]

not that any of you closed minded morons will change your opinions after reading this, but how can i resist jumping into another pointless debate?

ABS only makes you stop faster if you are the kind of hopeless noob who mashes the brake pedal, locks the tires, and keeps their foot firmly planted until the car skids to a stop. if you actually have a good feel for the brakes, and know how to modulate the pedal yourself, a human can get much closer to the limit, and consequently stop much faster than an ABS system can.

unfortunately, the vast majority of drivers cannot be trusted to modulate the brake pedal, and therefore do need the computer to do it for them.

[colivart]

Nah, ESC is just for preventing loss of car control by messing with with the cars brakes even if you dont want to etc. ABS systems work by not letting a wheel move slower than other wheels, moving the brake pressurr away from the wheels that move slower or want to lock up. This is why you feel the vibration at the pedal.

A ABS car with 2 left wheels on ice and 2 on tarmac wont stop fast, but it stops straight, a bit like a differential

nah man you got it wrong. due to physics when a car is turning or accelerating all 4 wheels are turning at different speeds..

[hagenisse]

a human can get much closer to the limit, and consequently stop much faster than an ABS system can.
When people say something like this, I wonder if they ever have driven a car before.

Theres lots of things humans can do better than computers, but this is not one of them.

[Whiskey]

evilgeek: ABS keep the brake presure the closest as possible to the limit in each tyre, while a human would do the same in all tyres (of course the front tyres will have about a 60% of total stenght)


PS: this was discused many page ago

[Byku]

Guys it also depends where. On dry tarmac it might be faster but on sand... not really :scratchch.

[freddyalek90]

OH NOES! NOT AGAIN!
We have had plenty of opinions in the pages before on this subject, please read them. :D


About the ABS + Burnouts subject, here's my 2p:
ABS should stop any wheel from blocking, but it engages only with speeds like 10+ kph. So, IMHO, it can work only if the speedometer doesn't move when you spin the wheels, or if it stays under that speed.

[evilgeek]

evilgeek: ABS keep the brake presure the closest as possible to the limit in each tyre, while a human would do the same in all tyres (of course the front tyres will have about a 60% of total stenght)


PS: this was discused many page ago

i know it was, but you didn't get it then, and you still don't.

ABS absolutely DOES NOT keep the brake pressure as close to the limit as possible! If it did, there would be no grip left over for turning. A human driver in a non ABS car can brake all the way to the threshold when braking in a straight line, but must lift off slightly in order to turn and brake at the same time. An ABS car always keeps far enough away from the threshold to allow adequate grip for turning, even if you don't need to turn, and consequently sacrifices ultimate straight line braking power.

Furthermore, there are plenty of well known examples of a skidding tire actually stopping faster than a rotating one, and a human can make a judgement call as to whether they are in one of those situations, while ABS will always assume that skidding is bad.

[Hallen]

i know it was, but you didn't get it then, and you still don't.

ABS absolutely DOES NOT keep the brake pressure as close to the limit as possible! If it did, there would be no grip left over for turning. A human driver in a non ABS car can brake all the way to the threshold when braking in a straight line, but must lift off slightly in order to turn and brake at the same time. An ABS car always keeps far enough away from the threshold to allow adequate grip for turning, even if you don't need to turn, and consequently sacrifices ultimate straight line braking power.

Furthermore, there are plenty of well known examples of a skidding tire actually stopping faster than a rotating one, and a human can make a judgement call as to whether they are in one of those situations, while ABS will always assume that skidding is bad.

Wow, talk about overstatement and absolutes...
and yes, this has all been discussed already.

ABS does allow average drivers to be able to turn even during a panic stop. However, to make the assumption that modern ABS systems are braking way under threshold to do this is misguided.

ABS doesn't care if a car is in a turn or not. It reacts at what, 100hz? for modern systems. If a tire locks up, like your inside front tire in a turn, it reduces brake pressure to that corner. It doesn't care if you are in a turn, it will adjust braking as necessary to not lock a tire. The reason ABS allows you to turn while braking is because tires are not locked up not because it is braking way under threshold. ABS will apply the maximum braking it can without locking a tire weather you are in a turn or going straight. (people are still hung up on older, like pre 1990, ABS systems that were simple, sometime only two circuit, designs that didn't react very well or very reliably. These older systems could be out-braked by a good race driver. Newer systems just aren't that way.)

Every tire/road surface combination will have different optimum braking slip angle. In some cases, I suppose that a locked tire will stop just as fast as a tire at the optimum slip angle, but those situations are pretty rare.

Humans have to face the fact that given the right technology and the right optimizations, a computer is going to be able to do something like threshold braking better than a human can. Humans can adapt, where computers can't, that is true. But even in racing, the right ABS system will do a better job and a more consistent job than a human will. (And don't start with the "but x race series/car doesn't use ABS therefore the driver must be better at braking than the ABS" crud. The reason ABS is not used in most situations is because the rules don't allow for its use.)

[evilgeek]

we had a spring snow storm here last night, and the roads were very icy this morning. i drive an '06 vehicle with all the computer gadgets you like, ABS, traction control, stability control, AWD. i hit a patch of ice approaching a 4-way stop, the ABS kicked in immediately, and i went straight on through the intersection with no ability to slow down whatsoever. there as an other vehicle behind me of similar size, but obviously older and without ABS. when he hit the same patch of ice, he locked his brakes and got completely sideways, but got it stopped in time, just as i would have in any of my older vehicles.

i do believe the computer in a fighter jet can outfly a human, but when it comes to vehicles that don't cost $10's of millions i'm far from convinced.

[Byku]

Well as it was mentioned before. It all depends on what are You driving. On tarmac, new ABS system can be definitly better than human. On ice/snow/sand/gravel etc it's not so good.

[Neilser]

ABS doesn't care if a car is in a turn or not. Well said! I've run out of energy to convince the inmates :)
People who think they can beat the ABS should just pull the damn ABS fuse and amaze themselves with their own skill ;)

Jeez, there was even a guy on another thread saying how the F1 drivers were so good they didn't need TC and were all faster now because it was gone. (Ehhhh... so why didn't they just switch it OFF in the TC years?)

No amount of data will convince these people... :shrug:

[hagenisse]

(And don't start with the "but x race series/car doesn't use ABS therefore the driver must be better at braking than the ABS" crud. The reason ABS is not used in most situations is because the rules don't allow for its use.)
There are series where its allowed, but if used, you get a 50kg weight penalty. I wonder why...

[NightShift]

amaze themselves with their own skill ;)

They usually amaze someone else as reality strikes back when they least expect it.

[Hallen]

we had a spring snow storm here last night, and the roads were very icy this morning. i drive an '06 vehicle with all the computer gadgets you like, ABS, traction control, stability control, AWD. i hit a patch of ice approaching a 4-way stop, the ABS kicked in immediately, and i went straight on through the intersection with no ability to slow down whatsoever. there as an other vehicle behind me of similar size, but obviously older and without ABS. when he hit the same patch of ice, he locked his brakes and got completely sideways, but got it stopped in time, just as i would have in any of my older vehicles.

i do believe the computer in a fighter jet can outfly a human, but when it comes to vehicles that don't cost $10's of millions i'm far from convinced.

Seriously, that's one data point in a highly uncontrolled situation throwing in a whole bunch of assumptions that don't correlate.

The reason your ABS kicked in is:
1) You were driving too fast for the conditions
2) You did not start braking soon enough given the conditions
3) There was 0 grip so it didn't matter if you were using ABS or not using ABS, you were not going to stop (see points 1 & 2 above)
4) The vehicle behind you had to be built prior to something like 1990 to not have ABS. They obviously lost control which put their tires on complete different surfaces than what yours were on. Also, you have no idea what the speed of the other car behind you was when they started braking and if they had on better tires for the conditions than you did. You would have also lost control if your ABS was not on.
5) Ego is the biggest reason for vehicle crashes
6) You live in a cold place. You best figure out how to drive in snow and ice before you kill somebody.

[Napalm Candy]

Yesterday, under rain, with my car I tried to brake hard in a corner. The reaction it is not like LFS. In LFS when ABS is activated the car oversteer too much, in RL the car have a little understeer

[senn]

which car, and what settings for the brake pressure + bias, also were you compression braking? I tend to find the ABS when activating @ full pedal depression causes understeer, unless you do something really odd with the bias etc..even then it should compensate to some extent. Perhaps compression lock with weird diff settings? (altho with ABS activated, and braking, compression braking can't lock the drive wheels too much, as the ABS starts backing the brake pressure off on those wheels)

yeah i can't work out why the backend would step out....maybe even a replay would help, with the setup..

[e2mustang]

yeah i can't work out why the backend would step out....maybe even a replay would help, with the setup..
Maybe a few months earlier i had to brake very very hard to avoid an accident with my car,and my back end went out a bit and i had to oversteer(or corrigate,however you say it) this was becouse my rear calipers are a tiny bit stronger than the fronts+i was braking from 70 mph to almost standstill.

[bbman]

Maybe a few months earlier i had to brake very very hard to avoid an accident with my car,and my back end went out a bit and i had to oversteer(or corrigate,however you say it) this was becouse my rear calipers are a tiny bit stronger than the fronts+i was braking from 70 mph to almost standstill.

You should REALLY get your brake bias right, that's outright dangerous! :really:

[e2mustang]

You should REALLY get your brake bias right, that's outright dangerous! :really:
No thank you,im fine with it,i dont rly use brake anyway,only full throttle:thumb:

[DragonCommando]

I realy think some people overestimate the technology behind modern ABS.
All they did was add channels and speed up the pulse rate.

Quite litteraly, ABS still functions on the same principal as older ABS did, it just modulates faster and can adjust each wheel seperately.

When ABS pulses it takes brake pressure away from the locking wheel. It doesn't do it just enough to prevent locking though, it fully pumps the brakes on each wheel individualy, and faster than a human could.

This means that each wheel is not at optimal brake force all the time, only for the brief period that the ABS system crosses over from active to passive, then the wheel begins to lock again and ABS becomes active on that wheel again.

People forget one major detail about the debate if ABS stops faster or not. And that is the brake balance of the car. Most cars come from the factory at 80/20 F/R brake balance, this is so people cannot lock the rear wheels and swap ends. This does however have an impact on the deceleration during threshhold braking, because you can't use all of the rear tyre's traction before you go over the fronts.

If you took the same car and adjusted the brake balance so that it was optimal for the same straight line stop they use for ABS testing, I belive that a human would be able to use the grip of the tyres for longer than an ABS system does and thus stop shorter. But they have never done and never will do that test, because it isn't optimal for all conditions.

It is safer to set the brake balance forward and apply ABS than it is to adjust the balance optimaly and assume that the conditions will be optimal and the driver will know how to threshhold brake.

[NightShift]

All they did was add channels and speed up the pulse rate.

And add EBD. So they can increase pressure as they see fit, and adjust the braking bias accordingly :shrug:

[BoneCrusher]

well, let's get involved in the abs discussion too.
ABS systems have only sensors on the wheels to measure the rotation of them. As soon as a wheel locks, it reduces the brake pressure to that wheel, so it starts rotating again. ABS can do this to all wheels seperate. Something you can't by pump braking, which affects all wheels.
Braking with the left side on ice and the right side on a road, will make the car want to turn away from the ice, this is only prevented by the right rear wheel which will get a lot of sideways force to handle. If that force is large enough the car will slip sideways, no ABS can prevent that. Simply because it can't measure when that happens.
ESP (electronic stability program) add's a motion sensor to the system, so the controller 'knowns' if the car is accelerating, sliding sideways, turning, or rotating in the vertical axis. This system CAN adjust the brake pressure to the grip wheels if it detects the car is trying to spin.
A 'normal' ABS simply can't because of the lack of motion sensors.

[hagenisse]

I belive that a human would be able to use the grip of the tyres for longer than an ABS system does and thus stop shorter.
Why? :shrug:

[DragonCommando]

Why? :shrug:

Read the whole post, the answer is in there.

[hagenisse]

No matter the brake balance, in a turn, a abs system can release pressure to the inner front wheel, while braking the other wheels as hard as possible. How are you going to do that with 1 pedal.

[freddyalek90]

No matter the brake balance, in a turn, a abs system can release pressure to the inner front wheel, while braking the other wheels as hard as possible. How are you going to do that with 1 pedal.

Someone would say:
"You aren't supposed to brake AND steer. You could just lock the brakes, turn your wheel, release the pedal and swerve around the obstacle. ABS is for n00bs, real drivers don't use it etc etc etc."
I say: maybe if you are a racing driver on a racetrack you don't need it, but on the road...
I can't consider myself a perfect driver (as I've got my license for an year), but I can say I know what I'm doing. Of course, playing LFS has helped. And ABS has saved me from a crash several times.
Ok, on ice it doesn't let you stop. And locking the wheels does?
Ok, if you go straight, it doesn't stop you faster. At least, the next time, you'll have got enough tires to stop safely.

[DragonCommando]

No matter the brake balance, in a turn, a abs system can release pressure to the inner front wheel, while braking the other wheels as hard as possible. How are you going to do that with 1 pedal.


If it did that, the other wheels could/would still lock. more than likely they would as you are now using the tyres for more than just stopping, the grip is now devided between turning and stopping. ABS will act on all the wheels during a turn if you are going past thier traction limmits which is when ABS will kick in.

ABS allows you to push the brake pedal and steer while braking, that is the point of it. It allows you to go around the hazard instead of hitting it.
I can say that a million times, and people just don't get it. ABS IS NOT SUPPOSED TO MAKE YOU STOP FASTER! It was and still is intended to help the driver, whatever thier skill level, maintain control while steering and braking around any hazard on the road.

That doen't mean it won't make the average car stop faster on a dry level road. I've said it before, its a side effect of the ABS design.

However, if you took a car with optimum brake balance and put a good driver behind the wheel, that car will stop faster than the same car with ABS and a driver with a lead foot.

This is because regardless of how fast the ABS works, or if it can increase and decrease pressure, ABS has to back off the pressure and re apply it, during that time, the wheels are not at optimum brake force. It may only be a fraction of a second, but when that happens twenty times a second it starts to add up.

If you read my last post properly you would have also read:
"It is safer to set the brake balance forward and apply ABS than it is to adjust the balance optimaly and assume that the conditions will be optimal and the driver will know how to threshhold brake."

[MikeB]

ROFL, you really must be bored. Let me cite myself from about 3.5 months ago:
Gee, it gets so boring to read the same arguments about what ABS is and what not on every single page again...

Same arguments still being thrown at each other :really::thumb:

[NightShift]

How are you going to do that with 1 pedal.

Don't you know the very skilled driver can pull off any trick? :tilt:

[Neilser]

Don't you know the very skilled driver can pull off any trick? :tilt:
But hagenisse is still in that "I'm sure they'll respond to a rational argument" zone that I was in about a zillion ABS-thread posts ago ;)
Give it time...

[hagenisse]

Yeah ok.. I give up aswell. :shrug: