Vibration in antilock brakes during rainy weather


#1

I have a 2003 Toyota Solara SLE V6, and everytime it is raining (I live in San Francisco) and I am braking, driving down hill only, and come to a stop, my brakes vibrate, groan and seem to want to force the brake pedal back up. I have to step hard on the pedal to keep this from happening. Toyota tells me that this is the normaL behvior for the antilock brakes. That they are working correctly. I’ve never had these types of brakes on a car before but I can’t believe that this is normal. If so, why does it only happen during wet and rainy weather? Also, this almost never happens while driving on a level street. There the brakes behave normally.


#2

They do that to avoid a skid. It is the brakes releasing and reapplying. On level and dry roads, there would be no skid so the brakes work like all the other brakes you have had before.


#3

the vibration IS normal…practice hard stopping in a parking lot to get use to the vibrations…never pump anti-lock brakes.


#4

The previous post is 100% correct.

What you’re feeling are the brake valves cycling to keep the brakes from locking the wheels (skidding.)
It’s simmilar to the action of pumping the pedal, but the computer handles it, and can react with much more speed, as well as control each wheel individually.

This is normal for Anti-Lock brakes

Always let the computer do the work. If you need to stop fast, or in slippery conditions, or feel a skid is imminent, apply steady hard pressure to the pedal. It will vibrate, pulsate, and make noise. This is normal. If you pump the brakes manually you will mess with the ABS’s cycle or worse, disable the ABS.

You will come to get used to it in time. Everyone does.

And it does not do it on level ground because it takes more effort to brake going downhill. Just because you have to apply more braking to stop going downhill doesn’t mean the tires magically aquire additional traction. You have to brake harder but the tires only have the same amount of traction as normal. Throw in the slippery surface caused by rain and bingo, you have a skid.

cue superman music Here comes ABS to save the day!! =)

No worries my friend. None at all.

-Matt


#5

This is definitely normal for antilock brakes. It happens on my car whenever the ABS kicks in. What is happening is this:

A computer monitors the wheel speed of each of the 4 wheels. If one wheel is moving much more slowly than the others, the computer knows that wheel is skidding. When you push on the brakes, the computer pulses the brakes on that wheel several times a second.

Because of the pulsing, the brake pedal can feel a bit strange, vibrating or whatnot.