PeteL

Need help diagnosiing a problem.
There is vibration in the front when I brake at higher speeds.
There is no vibration while traveling, the pedal does not pulse as if the rotor were warped.
Both calipers are recently rebuilt, the vibration was there before the rebuilds. So, now I am at a loss. Appreciate some suggestions.

Z-man

Sometimes you get a vibration without a pulsing of the brake pedal if the rotors are warped. I'm guessing that's the problem.

Other problems could be your wheels are out of balance, or you need a front end alignment.

-Z

xsboost90

sounds like rotors- also make sure your front end is all tight.

BlueDog944

I've had that after a weekend of lapping at the track. Brake material build-up on the rotors from some hard and/or high speed braking. Can also happen if you've heated up the rotors really good and hot, then held the brakes momentarily when stopped, pads will actually start to burn or glaze the rotors. Solutions was to just drive the car in normal street driving and a few days later the rotors cleaned themselves up.

Chwatson

I've heard that certain bushings in the rear end can cause that shudder. Is the wheel shaking, or just the whole car kind of shuddering?

Sorry I couldn't be terribly helpful. Can anyone elaborate on the bushings I am thinking of? (i believe that they're easiest to get to during the torsion bar adjustment procedure) But I might be totally wrong.

Z-man

Chwatson - Perhaps you mean wheel bearings. They do go on the fronts - but that's more of a high frequency vibration when turning.

-Z

Techno Duck

You can sand both sides of the rotor surface with garnet sand paper (wood working sand paper). You will then need to re-bed the pads as you would a new set. This will get rid of the uneven pad deposits.

tjbreen

I had this same problem after a hot August track session and some standing water on the track. Didn't notice while driving on the street but the pedal was pulsing at the next track session and it got worse with heat. I had the rotors kissed on the lathe. Machinist said they were slightly warped and to avoid heating the rotors and driving through puddles. Rotors still have approximately a 0.9 mm to go before they are at minimum thickness.

PeteL

If I had to guess, I am thinking the rotors as well.
When the car is off the ground, and I spin the front wheels, there is an ever-so-slight point of rotation where the rotor hits the pads.
I am guessing that at the higher speeds, when I tap the brakes, this is what is causing the vibration. It is definitely in the front end.
I will pull the rotors, and have them checked for true.

lucifer_sam

http://www.stoptech.com/tech_info/wp...rakedisk.shtml

this is a good read and might be applicable to your situation.



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LS
'89 S2