Date: Tue, 03 Dec 2002 19:26:55 +0000 From: Grunff <grunffnopsam.com> Subject: Re: Brakes pulsing
Brian wrote: > A few weeks ago I replaced my front rotors with ATE PowerDisc rotors > (they have slots on the surface) and pads with OEM pads on my 1988 > Saab 900s and after giving them some time for the break in period > (about 50 miles being really soft on the breaks) I made 3 400 trips in > a 2 week period. After the car sat for the weekend; on the return 400 > mile trip when braking the car gave a shimmering feeling that felt > like anti-lock brakes. the car doesn't have anti-locks so I don't know > what to think. I don't think the rotors are warped and I also noticed > that the wheel alignment so it pulls to the right and the the lower > ball joint on the left frong needs to be replaced soon. Could any of > these things be causing this anti-lock break feeling? Or could I just > be feeling the pads gripping the slots on the surface of the rotor > after 1200 miles? My guess is warped rotor(s), it's too much coincidence otherwise. When fitting the new rotors, did your clean the mating surfaces thoroughly? Even a little bit of dirt/rust can result in the rotor being say 0.5mm at the rim, which causes a lot of wobble. Alternatively, stopping the car after heavy braking, when the rotors are really hot, can easily cause them to warp. A worn balljoint can certainly cause vibration, but it's easy to test whether it's the brakes. Jack up the car, put it in neutral, and spin the front wheels, one at a time. Feel for any drag along the 360deg rotation. If you can't feel any, get someone to gently touch the footbrake, until the fronts are just starting to bite. Now spin the wheel and feel for uneven drag. If you detect any on either side, then it's your rotors. If not, then it's something else. Slotted rotors don't normally produce this effect, and they certainly shouldn't. -- Grunff
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