EXNAVI Bicycle hydraulic brake caliper piston oil leakage repair parts maintenance upgrade kit for Shimano SLX M675 M7000 M7100 XT RS805 M785 M8000 M8100 XTRM9020 R9170 M9000 M9100 calipers, Black

I was having issues with my M785 series Shimano XT front brake caliper leaking and contaminating my brake pads. Took a chance on these as they were cheap and could be delivered quick. Pulled the original pistons out and discovered the problem was the ceramic was broken and chipped. It's a whole process as you have to take apart the caliper and completely re-bleed the system. This kits comes with all the new o-rings you need to rebuild the caliper like new. Fast-forward over a year and now having the same issues with the back calipers: broken ceramic piston. Came here to purchased the same resin set. Best part is there is no ceramic to break. Not sure how well the resin pistons will hold up "long term" but I've been riding the front set for over a year now.

I needed to replace the pistons in my GRX disc caliper as one cracked after pushing my brakes past their limit on a very tough (read dumb) ride. The caliper disassembly and rebuild was straightforward with the pistons and piston seals. I did not use the kit’s smaller o-rings. After a couple of fluid bleeds, the brakes pumped up nicely and my original lever feel has been restored. I do not see any leaks or reason to believe they will start leaking. Although my measurements show the EXNAVI pistons as 0.01mm larger than the OEM version, be mindful that 0.01 is within the error of this type of measurement tool and technique. I run a machine shop and have done a ton of mechanical repairs in all sorts of machines over the years and had no qualms about dropping these replacement pistons in. Although I can’t specifically pinpoint the exact material these are made of, it does appear to be a ceramic. I would even say that the surface finish appears to be smoother than the OEM pistons - perhaps that’s a good thing? Overall, If I ever need to repair another caliper, I would have no hesitation to buy this kit again.

Purchased a while back, didn't use them and thought I'd try them on a new caliper. Just wanted to post for anyone looking for a set for BR-RX400 grx. They are to big for the housing of the piston and piston seals.

The pistons fit perfectly inside the R9170 existing seals. I did not try to replace the original seals with the included ones so I can’t vouch for the fitment but overall I am super happy with the product and ease of installation!

Hace dos meses que los tengo y asta ahora funcionan bien.