Hydro rim brakes nearly sent me into a guardrail on Mariposa Street yesterday

I was coming down a steep hill in Sausalito, pulling on the levers like normal, and then the rear brake just locked up out of nowhere. Skidded about 20 feet before I could get my foot down, almost hit a parked truck. Turns out a worn pad had wedged sideways and seized the piston in the caliper. Has anyone else had a caliper piston stick like that on an old Shimano road setup?

3 comments

3 Comments

maxl9317d agoTop Commenter

Buddy of mine had this exact thing happen on an old 105 group a few years back. He was coming down Twin Peaks in SF, same deal - rear caliper just grabbed and wouldn't let go, locked the wheel solid. Wrecked his rear derailleur when he slid into a curb and bent the hanger. Turned out the old grease in the caliper had turned into basically glue, seized the piston up.

paul_ramirez17d ago

Honestly, that grease turning to glue is the real culprit on those older Shimano calipers. Ngl, it's a design flaw they never really addressed because once that piston seizes, you're basically riding a time bomb. Tbh, the fix isn't too hard if you catch it early - you can pull the caliper apart, clean out all that old crusty grease, and put in some fresh lithium or silicone grease on the piston. But the problem is most people don't know to do that until it's too late. And on a steep hill like that, there's no room for error. Glad you didn't hit the truck, but honestly that's a scary reminder to check those old calipers before you head down any serious descent.

shanec6117d ago

Is it really fair to call that a design flaw though? Shimano made a ton of those calipers and they worked fine for years for most people. The issue is more about people not maintaining their bikes. If you let grease sit for a decade and turn to sludge, that's kinda on the owner. Same thing happens with car brake calipers if you ignore them long enough.