The last couple of days, when i was driving at night, and pressed on the brake to slow down from about 100, i feel a bumpy feeling in the brake pedal. Usually goes on for a bit till it seems like they cool down or something. At low speed i sometimes get it. Any clue what this could be from?

 

check the brake pads and the rotors

 

And bleed the brakes.

 

ok i gust learned this in school. you might need new brake pads and brake disk or rotors. look at them so see if there is any bumps on them.

 

warped rotors.

 

sounds like warped rotors to me

 

well does it have rear disc or drum? because the rear is wraped when you feel it in the pedal and not the steering wheel. check for run-out with a dial indicator. you might be able to turn the rotors on a brake lathe if they are not too thin. good luck.

 

Crap ... thats what a I was thinking about too ... any know cheapest place for new rotors?

 

Have you had your wheels off recently, and the pulsing pedal started after that? If that's the case, you may have torqued the wheel bolts incorrectly, if not warped rotors.

 

ive got a warped rotor and it causes the whole car to shake now. must be fairly warped.

 

I just read an article (damned if I can remember where it was though) from a very good source. In their opinion, due to their own testing, there is no such thing as a warped rotor. What is actually happening is that pad material is being transferred to the rotor, and that is what is causing the issues. I was convinced that my Audi had a warped rotor due to the description posted above, but I followed their advice and it worked like a charm. Now my brakes are silky smooth again, without changing any parts.

The easiest way to develop this problem goes something like this. Braking from high speed, you come to a complete stop (while the rotor and pad is still hot) and hold the brake on. When everything is hot like that, you get the transfer of pad material to the rotor. Now the next time you brake, you get that shudder. Another way is to set the parking brake while hot. Same results.

Their recommendation, and what worked for me, was to re-bed the pads. Take the car up to about 80, and brake very hard (just short of locking them up), but release them before you come to a complete stop (otherwise you begin transferring again). Repeat this process many times. At this point, you are attempting to "grind" off the pad material that is stuck to the rotors. After a couple dozen times doing this, my brakes were good to go again.

In more drastic cases, you might need to put a more abrasive pad on their to accomplish this, or even have the rotors turned.

Somebody post the link to that blasted article please. It should be mandatory reading for all drivers.

 

warped rotors happen all the time, man. hell, even cracked rotors... dont run your x-drilled/slotted rotors through a car wash after harsh driving.

my rotors currently are warped, well the left side is because of a stuck caliper. gonna fix this when parts come in. none the less its very possible. heat / cold warps metal. therefor you have warped rotors, ie; driving hard then letting the car sit. this can cause warped rotors if they are old and thin, most rotors on cars of this age have been machined so thin its crazy. get some new ones and rock on, or have yours machined again, just be sure they are not too thin to do so.

rock on.

 

Well, before reading that article I would have been right with you on this matter. Either way, wether the rotors are warped or if you have pad material on them, replacing the rotors will fix it.

I know that somebody knows where that article is...

Found it!!! Read up guys, this is a gold mine of information. I was looking at over $500.00 in repairs due to "warped rotors" as diagnosed by an experienced shop. Fixed my issues myself after reading this, and learned a shitload about brakes in general. Hope this helps someone else out as much as it did me. http://www.stoptech.com/tech_info/wp...rakedisk.shtml

 

thanks kentetsu i will give that a go

 

500 bux for warped rotors? Thats rediculous! I change my rotors every 10000 to 20000 miles and it costs me max 30 bux a wheel!! If its a mechanic then I think its time to find a new one.

 

For the Mazda, I would agree with you. Audi is a whole different story though... They do make some cheap knockoff parts for them, but everytime that I've tried them and the Audi I've regretted it. When it comes to brakes, spend the money... Fortunately as I've said, I didn't have to change anything at all since I solved the issue myself.