Join Date: Apr 2010
Location: Canberra, , Australia
K100RT asymmetric brake calliper piston action
I noticed my rear brake pads were making a little noise when not braking, so I inspected the pads. One side nearly all gone, the other hardly worn. Decided to replace the pads.
(When trying to press the pistons back in with the calliper on the bike couldn't get at them, tried to lever with a screwdriver, chipped the leading edge of one of the pistons).
After taking the calliper off and pressing the pistons to flush with the calliper body, decided to check their action by working the brake pedal a bit. Sure enough, one wasn't moving.
Kept trying, repressing the moving one back in. The other one started working. Thought maybe a fluid flush might help - no difference. As I kept repeating, sometimes one would stall, sometimes the other. Sometimes neither. One side stalls more often than the other.
After many repeats I over extended one of the pistons and a bit of brake fluid leaked out of it. It then moved more freely, presumably from some lubrication from the fluid. Did the same to the other one. They both now move more freely, but still generally asymmetrically. I've extended and pushed them back at least a hundred times now.
Took them apart to see if I could get in to the innards of the pistons, but can't see how. Reflushed with fluid.
If I leave them both out about 3-4 mm from the calliper body they tend to work symmetrically, but not always. What's going on? Should I pursue stripping them down and cleaning and lubing them? If so, how, and what with? Their action is smooth.
I'm in Australia, where the cheapest second hand ones are $100 (the US ones would be that expensive by the time shipping is added). I'm told I can get a new one for $220 (to be confirmed). Any advice which way there? I'm on a low income at the moment, but I don't want to get a second hand one with seal or other issues.
Any advice welcome.