Vibration while braking

[993buyer]

I developed vibration in the steering wheel while braking with my 1994 964 Turbo Look (C4), sometimes very pronounced.
I installed new front end (tie rods, shocks, etc) in the past and it drove fine...
But very recently I installed new rotors and pads and new tires were installed about 2 months ago.
Wheels were balanced and car was aligned at that time.

What could this be? Warped rotors, wrong brake pads?
Any pointers appreciated. Thx.

[Cajundaddy]

The most common cause is uneven pad transfer to the rotors causing rotor judder which is a pulsing that feels a lot like warped rotors. Assuming the rotors were installed properly you *may be able to resolve this by carefully re-bedding the pads to get a nice even pad transfer and allowing them to cool very gradually overnight. If that does not work, having the rotors turned and then pads bedded should do the trick.

We do a lot of track work and if we end a session quickly and park the car with hot rotors, uneven pad transfer is likely and makes the weekend less enjoyable. It has happened a few times over the last 15 years, always my fault for stopping the car hot. Re-bedding the pads and gentle cool down worked 2/3 times. In the worst case the rotors were a gooey mess and I just replaced them and started over.

[wesleyc]

If the above information doesn’t fix it. Perhaps new control arm bushings. if you haven’t already replaced them they’re probably wore out.

[993buyer]

My mechanic is pointing to the rear spring plates. Not too sure as to how these can cause vibration in my steering wheel.
When I go the the extent to recondition/replace these, should I also recondition the rear-axle trailing arms?
I had not expected this, as the problem seem to have started, after I had new tires installed. Perhaps the balancing/alignment has not been properly done at the tire store?
I attach a photo of the trailing arm and it seems the bushing is shot.


Thanks.

[RedCoupe]

Cajun Daddy's advice is sound. I've also had bad brake judder when one or more pistons in a front caliper are sticking from corrosion or whatever.

[993buyer]

Thank you. I will check this out.

[Bigtoe32067]

It’s warped rotors. Just because they’re new doesn’t mean they weren’t stacked 25 boxes high and that tweaked them. I’ve seen it before.
Tony

[993buyer]

I will first stop by the tire store to rule out poorly balanced wheels...then have the rotors checked...

[RedCoupe]

Originally Posted by 993buyer

I will first stop by the tire store to rule out poorly balanced wheels...then have the rotors checked...

If you don't have vibration when you aren't braking, I fail to see how it could be wheel imbalance problems.

[993buyer]

Had wheel balancing checked. Right front wheel was off .5. Enough to cause vibration, l was told. The vibration is less, but still there. Next: check rotors for warping and seating of pads. control arm bushings and tie rods are newly replaced.