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The rear brake on my CX bike has started misbehaving. The lever has very little travel, and the pads are catching on the disc. After a race on Sunday, the rear brake was pretty much stuck on. Manually retracting the pistons restores the lever travel, but only for a few strokes before it's back to virtually no travel.
The pistons seem to move pretty freely - it doesn't take much effort to reset them. I've given them a clean, but it's made no difference.
My understanding is that when you apply the brakes, the movement of the pistons is just through the seals flexing, and the pistons only actually move through the seals to adjust for pad wear. Which suggests that rather than being "sticky" the pistons are actually moving through the seals too much as they're self-adjusting to be too close.
I'm tempted to strip the caliper and replace the seals, but I'm struggling to find the right parts.
there was a ropey batch with calipers not matching the levers and contaminated fluid. that would jigger your seals.
the master cylinder is dogmeat also. needs replacing as a service item.
Interesting. They've worked fine for a few years, but they do have a relatively hard CX life of mud and pressure washers.
I've read about issues with the MC, but struggle to see how it could cause these symptoms.
From a bit more digging, I think that this is the right kit for Force 22, despite the name:
https://www.sjscycles.co.uk/brakes/sram-red-22-700-b1-caliper-piston-kit-18-mm-rear/
... based on page 22 of this: