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

Had a cracked piston. Since shimano doesn’t want you to fix your calliper, I had to go third party.I cleaned the calliper to make sure there we no more ceramic chips inside it, installed seals and used mineral oil to lube new pistons while putting them into place.I let original pistons on the other half of the calliper. Since then (1 month)I rode my bike hard and had no issue. Pretty satisfied and have two pistons left.

Common issue with Shimano brakes. Looks like they just don't care? This issue has been going on for a LONG time. I have a set of M9120 and when I replaced the hose due to it getting caught and it developed a hole. When bleeding, it was leaking between the piston and the caliper housing. Sure enough, it was cracked. Bought these to see if I can salvage the calipers. They were a perfect fit and has been working great. I cleaned my old calipers in a 99% rubbing alcohol bath then blown clean with compressed air. With the oe pistons removed, there was a lot of ceramic dust mixed in with the fluid. After cleaning and wetting the new pistons with shimano mineral oil, they slid in and bled just fine. Lever feels the same and it's been working great. Absolute life saver. Ordering another set for when the front goes out.

Same diam as my saints piston. Using stock rubber thing. They also included a bunch of caliper gaskets. Good stuff actually

My Shimano Deore XT 4-piston calipers were starting to seize up on my rotor so I removed the pads to press the pistons back into the caliper body (see YouTube videos on this process). While pushing them in I could feel some grinding and realized the back side of the piston, inside the caliper, had broken. Shimano doesn’t sell the ceramic replacements so I bought AND some new calipers just in case. I figured if these replacements didn’t work, I would just replace the whole caliper. So now I have two brand new calipers sitting in boxes because these replacements work great. They come will all new seals. Once you remove the old pistons (see YouTube videos on this process), installing them is a breeze. And because they are not ceramic, I don’t have to worry about them breaking again in the future. If you’re handy, this is a great buy.

I had a crank in one piston on a Shimano XTR caliper. This replacement was perfect. I don't think it is mentioned in the description but all of the O-rings for a full caliper rebuild were included in the package.