So i almost got into a good accident today....idiot in front of me came to a complete halt in an intersection for no reason...really thought i was going right into him. Slammed on brakes but i noticed that when i did..my tires were screeching. Now i may just be stupid but with ABS..the brakes shouldn't be screeching like they would be if they locked up right? It sounded like my brakes locked up at the last second when i have ABS..what gives?

 

They shouldn't... kind of. It is possible that it was already in ABS and the tires were screeching at each pulse. ABS will kick in even more when it detects steering movement.

FWIW, the type of brake fluid you have will also determine how good ABS will work. Lower viscosity fluids are well-suited to it.

p.s. I'm glad you escaped the accident!

 

your tires are going to screech if you slam your brakes on, was it a solid screech or a pulsating screech? ABS works by pulsating the brakes so you can steer around the obsticle youre about to hit. it doesnt make you stop any quicker nessicarily.

 

It was a soild screech..thats why i was like wtf

And yeah ABS actually takes longer to stop than brakes locking up..but it's controlled

 

LMAO no accident is a good accident.....

 

That is incorrect.

If you lock up your brakes, ABS or not, you will take longer to stop than either ABS (pulsing between milliseconds of lock and then release) or by simply applying them manually to the very threshold of locking.




AS far as your ABS's operation, I'd take it out and test it in a safe, controlled area and verify its proper operation.

 

"On very soft surfaces, such as loose gravel or unpacked snow, an ABS system may actually lengthen stopping distances"

http://www.nhtsa.gov/cars/problems/e...absbrakes.html

So i guess it depends on what surface it is

 

uhmm . . . you do realize you're quoting the exception, not the rule, right?

(and hopefully, you noticed that even there, it said "may". More often than not, you'd still be better off even in those conditions. I think what they're getting at is, in those rare circumstances, if your car isn't allowed to lock the tires and scratch/break through the gravel or snow to a more solid surface underneath where it will have better traction (even in a lock) than the continual lock and release of ABS will allow from 'on top' of the soft surface.


More to the point though, were YOU in gravel or snow when you had to slam on your brakes?

 

I was in 6 ft of snow

 

i thought on a dry, clean, straight stop, a non-abs brake work better..

i believe car and driver did this test once..

 

mm hmm


Most definitely, when properly applied, non-ABS will stop shorter than the same set of brakes using ABS. If you've done any HPDE or racing type courses, they almost always teach threshold braking as a basic preliminary exercise before any fun stuff. Sometimes, they will even use the same car for back-to-back comparison; once with ABS enabled, and then again with it disabled.

Of course, anyone who grew up and learned their spirited driving skills waaaaaaay back before ABS was invented ( ) will probably know this just from experience.

 

It's a fact that the maximum static coefficient of friction (tires gripping due to ABS) is higher than the kinetic coefficient of friction (tires sliding) for all materials. If you have a poor implementation of ABS that doesn't bring your friction to the limit then it's possible your may not be reaching the maximum static coef. and would be better off without it... but a good ABS will almost always work better to a first approximation. There are much more minor second-order effects such as the dynamic effect of the changing pulsing forces that cause troulbe on ice and gravel as mentioned though.

 

Pardon my editing liberties.

 

Where you over (I think) 15mph? There is a minimum speed for ABS

hit 20-25mph and slam on your brakes you should get ABS to engage.

 

The question is, should the tires screech when the ABS brakes are slammed.

Yes, rubber on pavement can and will scream, even if the ABS is engaging.
If you are questioning whether or not they are functioning, then the question of "did the brake pedal pulse under your foot" comes in. It should feel (and sound) like the brake pedal is ratcheting under your foot.

Most often, if there's something wrong with the system, your ABS light would be on.
I figure, if you didn't hit the guy, they're working.