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Spinoff : general ABS discussion
(127 posts, started )
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
Quote from Not Sure :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.
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
Quote from Zen321 :[...]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?
Quote from emreerokyar :
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.
Quote from 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

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.
Quote from freddyalek90 :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
Quote from McTw1st :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...
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.
Quote from 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.

"[...]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
Quote from freddyalek90 :"[...]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.
:biggrinfl
Quote from sgb27 :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.
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.
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)
Quote from 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)

I must suck then.

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

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
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")

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
Quote from zeugnimod :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?
Quote from zeugnimod :I must suck then.

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

That explains it!!
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.
Quote from 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")

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).

Quote from DragonCommando :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.
Quote from Zen321 :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
Quote from Neilser :
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.

Spinoff : general ABS discussion
(127 posts, started )
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