evah40•13d agoMost Upvoted

Grease debate: copper vs ceramic on disc brake pistons

I rebuilt my XT calipers last weekend and used copper grease on the pistons like I always have. But a guy at the shop said ceramic grease is better because copper can cause the seals to swell over time. I put around 200 miles on them since and they feel fine, no sticking. Has anyone else seen seal damage from copper grease or is that just one of those things people say?

2 comments

2 Comments

james_ross13d ago

Nah, I'm gonna push back on the ceramic stuff hard. I've been running copper grease on my bike brakes for like 8 years now across three different sets of XTs and never once had a seal issue. The swelling thing is an old wives' tale that got passed around from the automotive world where they use different rubber compounds. Bike caliper seals are meant to handle mineral oil and brake fluid, a little copper grease isn't gonna magically wreck them. Plus copper is way better at heat transfer, it actually draws heat away from the piston and into the caliper body on long descents. Ceramic is basically just expensive anti-seize with some hype behind it.

lisa_brown13d ago

I used to be all in on ceramic paste, thought it was the smarter choice for seals. But your point about the rubber compounds being different for bikes vs cars actually makes a ton of sense, never thought of that. The heat transfer thing with copper is a solid point too, I've definitely noticed my brakes fade less on long downhill runs in the past. Might have to switch back and give copper another shot.