Tim_944

I removed my sticking front callipers and the piston has been removed. This is from a 1978 model with single piston caliber.

The piston looks shiny over to me except near the edge in the picture you can see what looks to be rust. also the part that is not in the bore is all rust. I assume I can just sand the part that does not go into the bore but the shiny part with some rust or material stuck to it I don't want to damage.

I have steel wool, scotchbrite, 600 grit sandpaper, and a Dremel with a polishing bit and polishing compound. not sure which to use and what to avoid. I don't want to damage the piston or bore and cause leaks.

the bore also has some material stuck to it (pic) or slight pitting, can't tell. I think the bore is less critical as the piston rides on the seal.

The Forgotten On

Just use 0000 steel wool to clean the rust off. It will remove it quickly without even so much as scratching the steel of the piston or bore.

It's what I used when I rebuilt a set of OB 928 calipers like you're doing.

Tim_944

also just noticed that the outer part of the piston (part contacting the pads, is larger on the piston that came out of the driver side when compared to the passenger side. is this normal?

Tim_944

what about the heavily rusted areas (not on the shiny piston part). I don't think steel wool will take that off. I will try out steel wool on the piston and see if it works.

I think my pistons are a bit more rusty than average.

Tim_944

I tried the steel wool and it did not work on the pistons. I tried scotchbrite and it is working but it will take forever to get it all off. also, can't tell if there is some minor pitting.

Bigfoot928

If the pistons are different sizes from one side to the other someone has switched a caliper on this 928. Both sides are supposed to be the same.

Tim_944

here is the picture. will this cause any braking issues? looks like the actual piston that rides in the bore is the same size but the outer part that contacts the pad is slightly larger.