This is my second Shimano Ultegra R8170 brake caliper with the same symptoms. It looks like some kind of corrosion of the caliper’s coating. I’ve read that sweat could be the cause of this. I always clean my bike after every ride. Still, I’m a bit concerned as if this could pose a serious threat to my health as in breaking bolts on a 70 kph descent. And is there something I can do about it to stop it from getting worse,… The first caliper was replaced by my lbs under warranty. I fear that this time it’s on me,…
by Marcus_Utrecht
8 Comments
What is your cleaning detergent?
I’ve stripped the paint on a caliper too when cleaning it (I think) years ago. Then put probably over 20’000km on it with zero issues. I wouldn’t worry about it.
Do you live by the ocean?
Are you sure some deranged mechanic did not put DOT fluid into it?
Fährst das bike auch im Winter. Das hat vom Salz und Wasser koridiert.
Remove the brake pad retaining bolt and apply new grease.
How hard and long do you bake?
Shimano icetech brake disks have an aluminum core that likes to melt for those that have a death grip on their brakes for the entire descent.
Almost looks like galvanic corrosion to me. Seeing it around the bolt is a strong indicator since that’s probably steel into an aluminum caliper. The lower part looks like maybe it rubbed on the frame and removed enough powdercoat from both parts to let dissimilar metals touch. Looking it up, I see that Shimano recalled Ultegra cranks for a galvanic corrosion issue and that other people have suggested it as a reason for similar issues with the calipers in the past.