IceWater

Ok, I know that actual rotor warpage is pretty rare and that pad transfer is usually the culprit when it comes to brake judder, but my question is how much runout is acceptable in a rotor? I developed a judder in my 968 driving out to the Glen for a DE, and it plagued me through the entire event and gave me a very inconsistent pedal. When I got home, I brought the rotors to work and measured them and got a total indicator runout of about .007" accross the entire rotor surface. Is that bad enough to cause a severe judder? I also suspect my bearings, so I'm going to check those too.

Thanks!
Tom

Waterguy

Factory specs for maximum run-out is 0.05 mm or about 0.002". Not sure if 0.007" would be enough for the kind of judder that you are talking about, though; I can't believe that you would have warped Porsche rotors driving TO the Glen.

IceWater

After some further investigation, I think I had a two part problem. First, my wheel bearings were a little loose. I tightened them up and the problem got less severe. But, I think the rotors are also bad. After doing the bearings, I drove around with the brake on for a while to get them hot, and sure enough, the judder started showing up again, though less severe. So, I ordered new ones and they should be here on Friday. They're $75 a pop at Paragon, which isn't too bad.

Thanks for the help,
Tom