930 brake caliper piston install

[stownsen914]

I’m rebuilding 930 calipers and having a hard time getting the pistons back in after cleaning everything up. In the past I’ve always just lubed with brake fluid for reassembly.

Is silicone grease the right stuff to use? Can it be any silicone brake grease product? Some of them seem to be intended for lining brake pads, etc.

[Ian Comerford]

I usually use red rubber grease for any caliper rebuilds. https://www.greasemonkeydirect.com/blogs/news/grease-guide-what-is-red-rubber-grease-used-for

[Bill Verburg]

Originally Posted by stownsen914

I’m rebuilding 930 calipers and having a hard time getting the pistons back in after cleaning everything up. In the past I’ve always just lubed with brake fluid for reassembly.

Is silicone grease the right stuff to use? Can it be any silicone brake grease product? Some of them seem to be intended for lining brake pads, etc.

any brake paste will do, some just use brake fluid as a lube

be sure that the outer seal aka dirt scraper has the printed part # facing in
use a flat faced pressure pad to drive the assembly in
check that the piston notches are correctly aligned w/ the pads, leading is stepped down

[stownsen914]

After reading some more, I decided it must be more of a technique problem than a lube problem. I was right. I tried again, still using brake fluid. I continued to use a block of wood about 6" long to drive in the pistons. I had noticed earlier that the pistons seemed to get cocked easily in the bores and jam up, so this time I gently rocked the block of wood back and forth while applying pressure. The pistons went in pretty easily this way.


Thanks Bill for the comment about the piston orientation. I noticed comments about that from another thread (notably that it's not the 20 degree orientation like two piston calipers use).

[Shaun @ Tru6]

I've rebuilt 6 sets now and while they're a little stiff going in, I just insert down to the seal and then twist back and forth pushing in, they slowly slide down the barrels.

Step orientation in the manual.