Can the brake rotor get seated too deep / grinding bad?

[Bendavis2]

I just was re-doing the rear wheel bearing on my early '83 944, and when I was re-assembling the wheel I came across something strange. When I mount the rotor, it feels like it's sitting too close to the hub. Sure enough, when I tried to give the axle a turn, the rotor started to grind against the metal. I pulled the rotor off, and found that apparently the rotor had been grinding away at the e-brake housing since it is sitting 3-4 mm too deep. You can see the bare metal that was ground away (between 3 and 4 o'clock while looking at the wheel). There's also part of the brake pad mounting bolt hold that's been ground up by the outer portion of the rotor (at about 2 o'clock).

There was too much scraping noise with the broken race in my rear bearing to have noticed this in the last few days, and I don't know if it happened recently, or if it's a recurring problem from the P.O., but based on the amount of wear, it almost seems as if the rotor has been slowly creeping close and closer to the bearing over a longer period of time.

And I missing some spacer I should have? I can't figure out what I should be doing differently, or what could be causing this problem.

I'd really love any ideas!



Ben Davis
1983 Porsche 944
Portland, OR

[Brando]

There's an inner spacer, where the splined shaft goes in from the rear to the trailing arm, a spacer tube between the stub axle and hub, then a final spacer between the hub and trailing arm. If one of those is gone you may be experiencing what you describe.

[Bendavis2]

Brando is right on the money!

Well, I guess I'll state what I figured out for the record, in case someone else has this problem in the future.

When my original bearing collapsed (it was the outside rear bearing), the inner race broke into a few dozen pieces, and the outer spacer ring slid into the bearing housing. This void allowed the brake rotor to seat itself deeper onto the wheel than before and that led to the grinding. When I opened up the wheel, I pulled out the outer spacer ring, and bagged it for re-assembly, but was following the clarks-gararge.com steel arm procedure so carefully, that I didn't realize the outer spacer was never called for. Really. It's not even in the exploded diagram on that page.

The only thing I can figure is that Clarks-Garage.com is referring to this Outer Spacer Ring as part of the 'hub' in his instructions. Either way, on first re-assembly I didn't put it in. But now it's in and it all works great.

[Jseuss]

I've experienced this problem almost to the letter with my '83 944 also. Will simply replacing the bearings do the job? is there any danger of the spacers being worn?

[Brando]

I'd replace all the bearings, spacers and seals in that instance, assuming the parking brake housing and stub axle are not trashed completely.