Front Caliper Problem?

dad911 · 07-13-2011, 01:41 PM

Never seen pads wear this bad:

99 Boxster. Both sides look the same, but this is the worst.

What's wrong? Pistons seem to work ok, they move with brake pressure, and there is not alot of drag when the pedal is released.

I also can't find rebuilt or new seals, just the dust covers. Are there any options other than new?

WhipE350 · 07-13-2011, 04:27 PM

Looks like either the top piston isn't working or the bottom one doesn't release properly. How quickly do they wear?

dad911 · 07-13-2011, 05:08 PM

Track car. Not sure of amount of track time, but I guess 3-4 days last season. They seem to work fine, which is why I'm stumped.

WhipE350 · 07-13-2011, 06:09 PM

So if you have someone push on the brakes that top piston seems to work just fine? I'm sure some other track person must have seen this before. I'd be curious myself what cause that. This chump is stumped

. It is kind of cool though.

very~worn~944 · very~worn~944's Garage

If the pistons truly do move freely, I can only ponder one scenario...
I can only assume based on piston size that the rotor rotates in an upwards direction as pictured? That caliper looks really grimy... What do the dowels that the pads ride on look like?
To me this looks like dirty improperly lubricated caliper assemblies , possibly non-factory pads with higher tolerances between dowels, and always hard brake application pulling the pads into the top of the caliper. The top contact point for the pad can't slide on the dowel (possible pitting also?) causing excess friction. The bottom half of the pad moves freely, without even contacting the lower dowel. The same hydraulic feed goes to all 4 pistons, the pressure would rather push what it can move.

It's my guess, but check those dowels! I wire brush and brake clean all contact points, then use small amounts of copper antisieze on select areas of the pad backingplate sides.

Let us know what you find!