I have a problem with my '90RS (90k miles, disc/drum), it vibrates when I brake from 40mph or higher... The vibration seems to come from the front end, but it's not shimmy, just vibration, even the dash top seems to bounce from it.... nothing vibrates when driving normally, just on the brakes, and more so if it's downhill...

It all started, when I got new drilled Rotors from Pure Performance, and a set of KVR semi-metallic pads. I also installed then Earl's Hyperflex lines(front and rear), and flushed out the old brake fluid, cleaned the master cylinder reservoir and refilled with Motul Dot3. I didn't want to pin the problem on the new brake parts, since the tires were worn and I needed to change the tie rods. So I started to check and replace anything that was not ok. So far I have done the following:

-Replaced the front bearings, when I changed the rotors, I have greased and adjusted them 3 times so far.
-I fitted Raybestos DS8022 backing plates on the pads, as per recommendations from KVR, because the pads were rattling.
-2 weeks ago, I replaced the inner and outer tie rods on each side, and replaced the Idler arm, the car was aligned after this change. All new parts were greased, as well as the ball joints.
-Last Saturday, I installed four new Yokohama A539 tires, had the wheels checked for wobbles, and the tire/wheel combos were balanced, the car was re-aligned (was ok from the previous week but was re-done anyway).
-Today (tuesday) the rear brakes reveived a major overhaul, with new brake shoes, the cylinders were honed, and fitted with new seals, the drums trued on a lathe, air bubbles bled off the system, parking brake cables adjusted.
-I replaced the rear shocks about 4 months ago.

The car has not been crashed, it is not "loose", nothing seems damaged underneath, the front shocks are ok, and the anti-sway bar is properly connected (vibrates when braking on a straight anyway). Anyone else had this problem??? I really take care of my car, and is one of the nicer ones around here, but this is driving me nuts... should I try some cheapie pads just to see if that works? should I replace the ball joints? Any ideas????

 

My professional opinion: Warped rotor. They always cause the shimmy thing.


Ed

 

Agreed. Maybe they overheated them when they cross-drilled them and never bothered to true them up afterward.

 

I thought so at first, but the pulsation is NOT felt through the pedal, and I have not overheated the brakes either; I followed the procedure for bedding in the rotors and pads properly, and the car has no shimmy, it just shakes, when braking from 30mph or higher...

I'll check to see if it is a warped rotor...