Rear Brake Contamination on Road Bike

[Bathroom_Security]

Hi, basically I keep having an issue with my rear brake (Shimano 105 Hydraulic disc) where it keeps getting contaminated. I think its oil, not entirely sure. It leaves 'heat' marks on the discs and it certainly looks like oil, that or its picked up st from the road.

I can only think its a seeping piston, although this has happened 3 times now and the pistons seem to function fine, no indication that there is air in the lines or its leaked oil. it does seem like a generous amount of oil (if thats what it is), I would certainly expect it to cause issues with the piston functionality or brake feel

Probably a pointless question but is a seeping piston obvious, or is it normal for brakes to pick up st from the road and basically become useless.

Ive had one 105 caliper fail on me entirely this year where it spewed oil out. Also had the same happen with an XT 4 piston on my mtb. Ive been careful with the pistons, ive always worked clean when bleeding brakes etc

Ive ordered an Ultegra caliper to replace it, plus new pads and a rotor as once they get contaminated thats it IME

Edited by Bathroom_Security on Friday 30th October 14:49

[frisbee]

The rotor should be recoverable. Scuff it with sandpaper to take the glaze off and clean it with alcohol.

My last brake that started leaking was from the hose join apparently, I wanged it up (because I had nothing to loose) and its been fine since.