86 Turbo

Looking to see if more experienced 944 owners have seen this issue.

Only after a short amount of miles my rear wheels have a LOT more brake dust on them than the fronts ever have and I want to sort out this problem. Both sidse show the issue. They are not really stuck in contact. I can spin the wheels by hand when they are in the air.

A little background info. My car is a 86 951 with about 35K miles on it now. I bought it two years ago. It had sat neglected for 14 years before I bought it. It was in pieces and I put it back together and got it on the road. The rear calipers were off the car in a box. The rears wheels have always had this issue since I got it back on the road. I have dealt with other issues and now am working on this one. It is stock. I put new rotors on it when putting it back together.

I have been under the car and there is no visible issue with the lines that lead back there. I realize the pistons could be stuck and not pulling back after brake application but it seems unlikely that both sides would fail the same way at the same time. Not impossible though.

Both sides have the proportioning valve as well as the master cylinder in common. Has anyone ever heard of a failure with the proportioning valve? Can it fail in a way that does not relieve the pressure?

I don't mind replacing the valve or rebuilding the calipers. I don't really want to fix things that are not broken.

Thanks

PaulD_944S2

Are the brake pads on the rear the same brand and type as the front?
It may just be a difference in the pad quality or type.

ealoken

I had to grind a litle on the side of the pads, so the would Ove freely.

86 Turbo

The pads came with the car. I do not know the specs but they appear to be the same from front to back.

gpr8er

Are the spacers/ washers in between the caliper and the mounting lug on the trailing arm? They go on the mounting bolt. It's a goofy setup that Porsche has going on back there, but it is what it is.

86 Turbo

Yes. The spacers are there.

I do appreciate the responses so far.

My gut tells me the caliper pistons are hanging up and not releasing. I have had stuck calipers on other cars but never both sides at the same time. Usually just one side sticks.

Has anybody ever had a proportioning valve fail and what was the failure mode?

ealoken

Tak out the pads, grind of some metall on the side. Make som room, i had the same issue on My 951.