"when possilbe avoid engaging the ABS" but why ?

Ice_warmer

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Every car manual I've come across, and I read 4 ... so far ... writes in some form or the another that the ABS should only be engaged when absolutely necessary. I've heard there's some valve on the hydraulic circuit that reduces brake pressure when the wheel starts locking, thus the bounciness of the pedal, but I'm not 100% sure on that. Why is that ?
 

Cowboy

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implied-facepalm.jpg
 

IceBone

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Because ABS engages when the wheels lock up, by letting the brakes off a bit and then reapplying it. The practical result of this is you won't skid uncontrollably, but the braking distance is increased. Applying just the right pressure on the brakes to not lock them up will make you stop a lot quicker.
 

thevictor390

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ABS should find the edge of your grip, so you get the maximum slowdown without lockup. But I don't think the system in most cars is precise enough. What IceBone said is true even in cars without ABS, a rolling tire has more grip than a sliding one.
 

narf

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I've heard there's some valve on the hydraulic circuit that reduces brake pressure when the wheel starts locking, thus the bounciness of the pedal, but I'm not 100% sure on that. Why is that ?

What ABS does is avoid locking up the wheels. The brake pad/disc combo can produce a lot more friction through pressure than the rubber/road combo, so in order to avoid locking up you need to limit the force on the brake pads.
In theory that does not increase the braking distance because the friction between rubber and road is maximized by staying just below skidding while the brake pad/disc can produce any friction while not locking up simply by altering pressure. To get that theoretical improvement in braking distance you need perfect controls though, and I bet many cars are not perfect.

Saying you should not engage ABS because the feel in your foot is better than the computer is not a smart thing to say in a car manual intended for the general public. I'd say 99% of the general public is not better at perfect braking than the machine, and about 80-90% of the general public is significantly worse.
 

Dr_Grip

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Saying you should not engage ABS because the feel in your foot is better than the computer is not a smart thing to say in a car manual intended for the general public. I'd say 99% of the general public is not better at perfect braking than the machine, and about 80-90% of the general public is significantly worse.

I think just because the general public is rubbish at driving, one should tell them trying to avoid triggering ABS (and other driving aids, like ESP) because otherwise they'll start relying on the driving aids to the point where they won't help any more.
 

narf

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I think just because the general public is rubbish at driving, one should tell them trying to avoid triggering ABS (and other driving aids, like ESP) because otherwise they'll start relying on the driving aids to the point where they won't help any more.

"Avoid getting into situations where you need driver aids"? Yes.
"Avoid fully depressing the brake pedal in an emergency braking situation to avoid triggering the ABS"? No.

If there is a penalty in braking distance from the ABS in your car (not the Kadett obviously :lol:) chances are the penalty for badly trying to avoid ABS by not pressing hard enough are far greater.
 

syncview

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ABS should find the edge of your grip, so you get the maximum slowdown without lockup. But I don't think the system in most cars is precise enough. What IceBone said is true even in cars without ABS, a rolling tire has more grip than a sliding one.


That is where EBD comes in.
 

Dr.Kamiya

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What ABS does is avoid locking up the wheels.

I think that's only true for newer cars. ABS from the 90's was a much simpler system where a wheel is allowed to lock up first, and only after that does the ABS reduce brake pressure.
ABS basically relies on counting a notched hub to find out how fast all of the tires are spinning. If one tire is spinning much slower than the others, then it's probably locked up and fluid pressure to that corner is relieved. Obviously there has to be a significant difference in the rotational speed of the tires before this can work. When you see crashed car with ABS you'll usually see a broken pattern of skidmarks, as the tires go skid-spin-skid due to the ABS.
 

thevictor390

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I think that's only true for newer cars. ABS from the 90's was a much simpler system where a wheel is allowed to lock up first, and only after that does the ABS reduce brake pressure.
ABS basically relies on counting a notched hub to find out how fast all of the tires are spinning. If one tire is spinning much slower than the others, then it's probably locked up and fluid pressure to that corner is relieved. Obviously there has to be a significant difference in the rotational speed of the tires before this can work. When you see crashed car with ABS you'll usually see a broken pattern of skidmarks, as the tires go skid-spin-skid due to the ABS.
My car's ABS system definitely allows some wheel lock before engaging, just ask the skidmarks on Route 146 from when some idiot in an SUV pulled out in front of me <_<
 

narf

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My description of the purpose of ABS already says that many cars aren't perfect in fulfilling that theoretical purpose :tease:
 

Ice_warmer

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I need to clear up the fact that I understand the principle of how ABS system works. I was asking that the abs system, that is how I've heard, has a valve on the brake line on each individual wheel and it lowers the pressure to the caliper - if the wheel is tendning to lock - so that it will avoid locking. BUT repetead valve usage aka ABS turning on the valve that reduces pressure will make high pressure on the brake line and in the long term may produce damage.

I understand that threshold breaking is superior to ABS, on a track. Although on the road it keeps the car under control under emergency breaking, driver assessing danger ramming the pedal to the floor - incidentally like i do - thus allowing the driver to have control of the steering.

The idea was if it produces long term wear?
 
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BBernes

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My experiance with the ABS on track use is that the system will overheat if you drive every turn with the ABS on.

I have tested this on a number of new and old cars, do not position yourself for a corner an trust that the ABS will save you.

The same goes for stability manegment systems, just a few laps driving whith the system engaged in every turn causes overheat and the system shuts down.

The stability manegment can also flatspot your tires as it tries to apply brakes to your rear wheel to stop your slide.

Do not turn off the systems, adapt your driving so you do not activate them.
 

narf

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Don't worry about excessive wear. I'm sure that every actuator has a certain service life and will wear out after a certain number of uses, but I'd guess not using it will cause it to seize up. Just like with brake discs, not using them will support rust.



PS: Obviously, track use may be different :)
 
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Cowboy

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I think just because the general public is rubbish at driving, one should tell them trying to avoid triggering ABS (and other driving aids, like ESP) because otherwise they'll start relying on the driving aids to the point where they won't help any more.

THIS!

Remember headlight guy? he once explained to me (after he attacked a corner at 100+kph) how it would be impossible for him to "skid of the road" as he put it , because his car had ESP :rolleyes::rolleyes:

Never sat foot in a car with him after that....
 

Cobol74

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The real safety point about ABS is if it engages - remember many drivers are never taught how to handle low adhesion breaking surfaces - is that you should be able to influence the direction of the car i.e. you can steer a bit.

The breaking distance over that a competent low adhesion driver obtains is significant, but it is certainly better than locking up completely (I know the hard way - shudders, I got away with it just) and all inputs to the steering and breakes are negated by zero adhesion - injury and/or death just waiting to happen.
 

IceBone

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The breaking distance over that a competent low adhesion driver obtains is significant, but it is certainly better than locking up completely (I know the hard way - shudders, I got away with it just)
I didn't...
 

narf

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The real safety point about ABS is if it engages - remember many drivers are never taught how to handle low adhesion breaking surfaces - is that you should be able to influence the direction of the car i.e. you can steer a bit.

Locking up the rear tyres without any steering input can spin the car as well, so braking with working ABS+EBD in a straight line is probably safer than without even if you don't need to avoid a deer.
 

equiraptor

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Do not turn off the systems, adapt your driving so you do not activate them.
I disagree with this, strongly. Disable the traction/stability control as you, the individual, are comfortable with. Realize that turning it oyf increases the likelihood of an off or spin on the track. But also realize that driving with the stability/traction control on means you don't have the opportunity to develop the car control skills that might help. Additionally, depending on the stability control system, you may be significantly slower around the track if you leave it on.

In one of my track sessions, with the stability control system on, I braked too late for a corner and turned in too late. My movements were also harsh. This put the car into a four wheel drift. The stability control lights flashed and flashed. But I'm not sure how much the system was actually doing - it didn't cut power (which the system in my car tends to do if the rear tires spin). It may have done some selective braking, but it still took the right steering and throttle inputs from me to keep the car on track and resumed pointing the correct direction. I'm not saying I could have saved it without the stability control, but I am saying the stability control alone couldn't have saved it.

Additionally, the stability control on my car only has one level. It's either on or off. The one setting it has is extremely paranoid, allowing no slip. The traction control will cut in before the limited slip diff on the car has a chance to transfer torque. Trying to track this car with the stability control on is torture. Smoothness doesn't help - some slip is expected to be used when tracking, and this system allows none (if it can help it). Thus, if the system in your car is like mine, I'd suggest turning the system off, and using low speed maneuvers to work on your car control skill. Just understand the risk you are accepting when doing this.

In cars with a more relaxed stability control, or with multiple settings, it would be wise to run with the stability control on sometimes, and off other times, so that you learn both smoothness (enforced by the stability control) and car control skills.

Again, I state, though, that turning off the stability control does increase the risk of damage to your car and yourself. Only do so if you are aware of the risk and ready to fully accept the risk yourself. In other words, if you turn off stability control and crash, it's not my fault. :p
 

narf

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In one of my track sessions, with the stability control system on, I braked too late for a corner and turned in too late. My movements were also harsh. This put the car into a four wheel drift. The stability control lights flashed and flashed. But I'm not sure how much the system was actually doing - it didn't cut power (which the system in my car tends to do if the rear tires spin). It may have done some selective braking, but it still took the right steering and throttle inputs from me to keep the car on track and resumed pointing the correct direction. I'm not saying I could have saved it without the stability control, but I am saying the stability control alone couldn't have saved it.

What it probably was doing was avoid that four wheel drift turning into a spin, most likely by single-wheel braking. It may also have perfected your steering, that's where you'd be absolutely correct by saying the systems wouldn't have saved it alone - the DSR in my car will only perfect my steering input if I actually steer, it won't know what to do on its own. Feels a bit weird, but works well... involuntarily tested it on a partially snowcovered Autobahn :lol:
Additionally, flashing through the entire corner may be caused by one tiny correction entering the corner, many systems keep flashing for a few seconds after the intervention.
 
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