Hi, I recently got new front disks and pads for my 91 964. After wards what was a little shudder quickly developed into an annoying shudder which was detectable from 60km+. My mechanic, a Porsche specialist, worked through the various options like balancing and a new set of disks but to no avail. Finally after approx 10 hours of work it was determined that one of the tyres was off round internally which was virtually impossible to see on the balancing machine. I replaced the front tyres with Bridgestone RE001's and eveything was great. It was like a new car.

This was only approx 1000kms ago. I now seem to have the same shudder returning. Very noticeable on the motorway at about 80km+. You can see the steering wheel shaking. I am the only driver of the car, I have hit no curbs or nasty pot holes and the problem is gradual so I dont think I've lost a wheel weight.

I'm loath to have my mechanic chase ghosts (at a price) so can anyone help with some idea's

 

Is the car usually parked for weeks?

 

no, daily drive, longest it's sat if 5 days since i got it

 

am confident it's not an off round tyre or flat spot

 

Front bearings? Do you use front spacers? If so, are they mounted correctly, and tightened the right way?

 

Very characteristic of improperly balanced wheel. Are your wheel weights on the inside? If so, you might not be aware if you lose one.

 

I've experienced something very similar and it seems to have been a result of brake pad material transfer to the disks (DE people seem to know more about this, but it apparently can also happen to street cars). What seemed to help alot was to (safely) perform several high energy stops from around highway speeds, to scrub off the deposited pad material. FWIW, I had Pagid Black street pads installed on new front disks when this started happening about 1000 km later.

Hope this helps.

 

If you like , put the spare tire on the right front , take it for a drive .
Then put it on the left front and take it for a drive .
What do you find ?

 

If its uneven pad deposition, the problem would only show upon braking. If its while driving, without the use of the brakes, have a close look at wheel bearings and front lower control arm bushings.

the bushings are a common wear item.

 

thanks everyone for your feedback