Shimano BR-RS505 pistons not moving the same amount

bikingjohn

I found that the rear brake pistons on my CAAD-12 Disc are not moving the same amount. That has forced me to move the caliper all the way to the left and still the pads are touching the disc.

Upon closer inspection, one of the piston was protruding one or two mm more than the other when "rested". I could see more of the "white portion" (ie. the piston itself) sticking out more.

Any way to fix it? thanks in advance for any suggestion.

bradsbeard

Did you get the Shimano tool supplied with the bike to push the pistons all the way back?

If so use this and then loosen off callipers retighten while holding the brake in.

If not maybe a bleed of the system.

bikingjohn

bradsbeard wrote:

Did you get the Shimano tool supplied with the bike to push the pistons all the way back?

If so use this and then loosen off callipers retighten while holding the brake in.

If not maybe a bleed of the system.

Yes, I used the yellow bleeding block to push it back in.

Maybe I will rebleed and check again.

The Rookie

Sounds like the piston is sticking, with calliper off the bike and pads removed pump the piston out (NOT TO FAR) and clean exposed part with alcohol, push back, pump out and repeat.

The issue is not it coming out unevenly but it not retracting, 99% of the time that's caused by some crud.