hard to move piston after caliper rebuild

SO I am putting rebuild kits on my newly powder coated calipers. When I installed the piston on the new seal it did not want to slide into the bore... I had to use a c-clamp with slight force, not to hard to press it in but it certainly did not slide right in. I could not press the piston in with just my fingers.

I am wondering if there is a problem with this. The last thing I want it to have to take the rear end all apart again to fix a mistake.

What do you all think?

did you use brake fluid as a lube to get the piston in place? if you did it just might have hydraliced a bit not a big problem that will happen sometimes on the other hand you may have rolled one of the seals out by accident.

Hardrock, is piston free in bore without seal? Is seal new? is seal land clean? any evidence of powdercoat in bore? i hate to suggest it, but powdercoating is a bake on process, and heat could distort bore. luck g

I really doubt the 450* used to powder coat would warp such a hefty piece of alum...

The boars are clean, I spent an hour washing every speck of grime out of the bores and grooves.


I did not use any fluid as a lube. I think this may be part of my problem, I am going to use DOT 5 but I only have DOT 3 on hand in the barn so I just went "dry".

Did you clean out the seal groove with a dremmel? I always do and use fluid as lube.