4 Piston Hydraulic Brake Repair Parts Upgrade kit Ceramic Piston Perfect Substitute for Shimano Brake Caliper 4-Piston M640 M810 M820 M7120 M8020 M8120 M9120

Because Shimano doesn't sell OEM rebuild kits for their calipers, I was forced to go aftermarket. Big mistake. These showed up and looked to be of fairly good quality. I installed these into a Shimano BR-M8120 caliper. Bled the caliper and everything appeared to be good to go.I get out on my first ride and the brake is working well. Then, I get some heat in it on some downhill and the brake goes completely away! I mean, lever to the bar with zero braking force! I get it home and think to myself that maybe there was a trapped air bubble in the caliper so I re-bleed the system and get it ready to go for the next ride.The next ride, something similar happened in that the brake is working well until I use it on some longer downhills. This time, though, I lose all braking force because the oil has gone past the seals/pistons and soaked the caliper/pads/rotor and wheel.I've ordered a complete new caliper from Shimano and I'm unable to return this junk because it's not in "new/unused condition".Save your $45 and put towards a replacement caliper instead.

The original ceramic pistons in my Shimano XT-8120 4-piston brake cracked at some point in time. I purchased the bike used, so I can't say it was me, but it probably was.I searched the web and found the same thing : Shimano doesn't offer replacement pistons.After complete disassembly and a thorough cleaning with non-chlorinated brake cleaner and 91% isopropyl alcohol, I left the original Shimano o-rings in place, used a little Shimano mineral oil brake fluid as assembly lube and put everything back together.I bled the whole system, put in fresh fluid and the brakes have performed flawlessly ever since. I have put 30+ miles over varying terrain (I am considered a Clydesdale rider = 200lb+) and have not had any issues with the brake I rebuilt.Very happy with my purchase.

I took my time disassembling and cleaning the calipers. I used shimano mineral oil during assembly and gasket sealer to put the two half’s of the caliper together. Plenty of rides on them now no problems

Funcionan a la perfección, ya los he usado para hacer enduro y funcionan a la perfección

Major fluid leaks after install