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I was setting up disc brakes wrong for years and didn't know it

I was doing a pad change on a customer's bike yesterday, a Trek Marlin 5, and the new pads just would not stop rubbing. I tried the usual stuff, loosening the caliper bolts and squeezing the lever to center it, but it was still off. My coworker, Mike, walked over and asked if I'd cleaned the pistons first. I hadn't. He showed me how pushing the old pads back in with a tire lever was just shoving dirt and old fluid back into the piston seals. He took a flat plastic tool, gently pried the pistons out a bit, and wiped them clean with isopropyl alcohol. After that, the new pads slid in and the caliper centered perfectly on the first try. I'd been skipping that clean step for ages because I thought it wasn't needed. How many of you make piston cleaning a standard part of every brake service?
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3 Comments
masongreen
masongreen20d ago
Honestly, that's the kind of simple trick that makes you feel like a total genius once you learn it, but a real dummy for the years you spent fighting it. Tbh I probably went a solid decade just mushing everything back in with a big screwdriver and wondering why my brakes always felt a little sticky. It's one of those jobs where skipping the five minute clean-up step just guarantees you'll waste twenty minutes trying to center the caliper later.
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benc53
benc5320d ago
A tiny bit of brake grease on the slide pins changed my life, no more fighting to get them seated right.
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masonbell
masonbell16d ago
Totally started using a q-tip with some isopropyl on the pistons after reading a tip from @benc53. Honestly it makes the whole job so much smoother and the pads just drop right in. Ngl I was definitely in the "just push it all back in" camp before that.
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