Anti-lock brakes

[thefeeloftheroad]

We have had some snow and ice in my state, the anti lock brakes seem to be working. How are anti lock brakes used? When the brake pedal kicks back do I let it go, press harder, what exactly?

 

[Natesriv]

keep pressing, don't release. It's designed to pulsate to let you know it's working (plus it's inherent in ABS design)

Press fully and don't release until you are under control or stopped.

 

[Natesriv]

They're used when the car's computer detects that a wheel is not spinning, but the car is not slowing down with enough loss of momentum...

It's a weird feeling, almost like your brakes are gone and it's metal on metal...but it's just a very fast application and release of the brake(s) for the affected wheels.

A lot of cars also utlize the brakes in their stability controls, where a single brake can be applied if necessary to bring a car back in control.

Watching Fifth Gear on Velocity Channel, they tested cars with the stabilty systems on and off...on makes the car almost impossible to lose control..off and it's spinout city!

 

[thefeeloftheroad]

Thanks, I kept on releasing the pedal, wasn't sure if that was correct. Next time i will keep pressing the pedal

 

[Natesriv]

No problem,

This British guy has some more info

https://www.youtube.com/watch?v=wWbDEgxln2c

 

[ChrisJ]

I've found often on ice or snow if you allow the ABS to kick in it will actually make you keep sliding where if you try to keep it from happening in the first place you'll stop faster.

Just something to keep in mind.

 

[Natesriv]

Yeah, drive slow!

I was thinking about that too... If all wheels are on ice and you stop, so all wheels stop spinning, but the car is still moving... does it know it's still moving and kick on the ABS??

 

[ChrisJ]

Yeah, drive slow!

I was thinking about that too... If all wheels are on ice and you stop, so all wheels stop spinning, but the car is still moving... does it know it's still moving and kick on the ABS??

Huh?

You stop, but the car is still moving?
Which is it?

 

[Palmaris]

I've found often on ice or snow if you allow the ABS to kick in it will actually make you keep sliding where if you try to keep it from happening in the first place you'll stop faster.

Just something to keep in mind.

This is how it works. When the ABS kicks in, it will take longer to stop then if you had a non ABS system. The snowier and sliperier it is, the longer it will take. If its really bad you will feel like you may never stop.

But the key is that you can now steer your car. If you locked up your wheels in a non ABS car, you will skid into whatever item is in front of you. With the ABS system, keep your foot on the brake, steer around the object you could possibly hit, you will miss it and eventually stop. That's how it will work.

 

[Natesriv]

Huh?

You stop, but the car is still moving?
Which is it?

All wheels are stopped (not turning) but car is still sliding..

 

[ChrisJ]

All wheels are stopped (not turning) but car is still sliding..

Not sure being the car has accelerometers

 

[ChrisJ]

This is how it works. When the ABS kicks in, it will take longer to stop then if you had a non ABS system. The snowier and sliperier it is, the longer it will take. If its really bad you will feel like you may never stop.

But the key is that you can now steer your car. If you locked up your wheels in a non ABS car, you will skid into whatever item is in front of you. With the ABS system, keep your foot on the brake, steer around the object you could possibly hit, you will miss it and eventually stop. That's how it will work.

Yeah,
Practically never.

 

[wbjones]

Thanks, I kept on releasing the pedal, wasn't sure if that was correct. Next time i will keep pressing the pedal

that was the way to stop in low traction conditions in the "good ol days" … i.e. before computer controlled ABS … you foot and your brain were the ABS ..

quickly releasing and re-appling the brakes was the only way to break the lock up that was occurring … the ABS module does the same thing, except much MUCH quicker (multiple times per sec) than your foot ever could …

so the pulsing feel that you're getting is the brake pressure being released and re-applied (multiple times per sec) to keep the brakes from being locked up

so .. yeah .. like the others have said … keep you foot pressed as hard as you can in a "panic" situation (or low traction situation) and the computer will do the braking for you

 

[ChrisJ]

that was the way to stop in low traction conditions in the "good ol days" … i.e. before computer controlled ABS … you foot and your brain were the ABS ..

quickly releasing and re-appling the brakes was the only way to break the lock up that was occurring … the ABS module does the same thing, except much MUCH quicker (multiple times per sec) than your foot ever could …

so the pulsing feel that you're getting is the brake pressure being released and re-applied (multiple times per sec) to keep the brakes from being locked up

so .. yeah .. like the others have said … keep you foot pressed as hard as you can in a "panic" situation (or low traction situation) and the computer will do the braking for you

I've tried to figure out if its just how people explain it, or if they were literally hitting and releasing the brakes?

Before ABS, which means up to 2012 for me, I would do what I call modulate my brakes rather than pump/release reapply? Releasing them seems totally counter productive and even scary. I would apply just enough pressure that they would start to lock and then let up just a hair and keep pressure fairly steady.

Are we talking about the same thing, or did people literally pump the pedal?

 

[ahtoxa]

I've found often on ice or snow if you allow the ABS to kick in it will actually make you keep sliding where if you try to keep it from happening in the first place you'll stop faster.

Just something to keep in mind.

ABS' isn't designed to stop you faster. It's designed to allow the driver to retain some degree of steering control while panic braking or braking during very low traction situations.

In fact, stopping with ABS takes longer than it does if you lock up the tires on dry pavement.

 

[ChrisJ]

ABS' isn't designed to stop you faster. It's designed to allow the driver to retain some degree of steering control while panic braking or braking during very low traction situations.

In fact, stopping with ABS takes longer than it does if you lock up the tires on dry pavement.

I disagree with you on that, in fact locking up your tires on dry pavement increases stopping distances dramatically.

Anyone that knows how to drive knows better than to lock your tires up when trying to stop.


http://youtu.be/0mR89sT0YfA

http://youtu.be/ly62FoZH_Dc

 

[wbjones]

I've tried to figure out if its just how people explain it, or if they were literally hitting and releasing the brakes?

Before ABS, which means up to 2012 for me, I would do what I call modulate my brakes rather than pump/release reapply? Releasing them seems totally counter productive and even scary. I would apply just enough pressure that they would start to lock and then let up just a hair and keep pressure fairly steady.

Are we talking about the same thing, or did people literally pump the pedal?

usually it's stated the way I did because most folk get lock up in "panic" braking … (not everyone … so leave me alone all y'all LOL )

and in a panic braking situation … modulation isn't something that most can wrap their heads around … at least at the moment … and releasing the pedal doesn't necessarily mean coming completely off and then reapplying … so it sorta becomes the same as you're saying …


keep in mind that the ABS is actually doing just that … completely releasing the pressure and reapplying multiple times per sec .

 

[wbjones]

ABS' isn't designed to stop you faster. It's designed to allow the driver to retain some degree of steering control while panic braking or braking during very low traction situations.

In fact, stopping with ABS takes longer than it does if you lock up the tires on dry pavement.

except that lots of race teams use ABS … if it actually meant longer braking I don't think they'd be using it …