Avid Juicy 5's - sticky piston even after rebuild and new seals?
Copied form another forum I'm on - just asking for more input!
Just rebuilt my spare set of Juicy 5's after deciding to fit them to the wife's bike, and they still have sticky pistons.
Yesterday I fitted new seals and pistons, and have just bled them but the outboard piston (one closest to the banjo) is still sticky. They will move if you hold back the other piston, but in normal operation they don't work properly!
Both calipers were cleaned before rebuild, new pistons and seals - all clean and lubricated with DOT fluid before re-assembly and bleeding.
You need to give them time to loosen up. Just align the caliper properly - without relying on the CPS method as your uneven pistons will leave the caliper off to one side or the other - and get some time on the brakes. If they're still giving you grief after a ride or two, then start trobleshooting...
What luck for rulers, that men do not think - Adolf Hitler
Make sure that the piston seal groove-seat is clean and free of oxidation build-up. Oxidation build-up in the seal seat was a real problem in older aluminum automotive and motorcycle calipers until some of the MFR's started to anodize their aluminum calipers or add a secondary seal over the piston seal on steel calipers. DOT brake fluid absorbs water and the oxygen in the suspended water oxidizes the aluminum in the caliper body. The seal seat is the most vulnerable to oxidation and contamination because it is directly exposed to water, dirt, brake pad dust and oxygen, which will push the seal into the piston causing it to stick.