Rebuilding calipers - getting piston back in bore

[cali-ti]

i've got everything lined up, new seals in place, but i'm having a hard time getting the piston back in the bore. anyone have any suggestions, tips/tricks on how to do this? it appears to take a large amount of force to push it back in. i don't have a large vise, but i was contemplating getting one anyway. is such a thing necessary? would appreciate hearing from those who have done this themselves. TIA

[cali-ti]

my new friend "bluey" the c-clamp got the job done. apply brake fluid to the new seals, bore and piston, slip the new seal over the top of the piston, working it down until the lip that needs to go into the lip on the caliper is hanging freely off the end. seat the lip into the caliper, then push the piston in tight against the rubber seal ring (which you've already put into the caliper) inside. use a c-clamp (with a piece of wood - i used a mouse trap with all metal pieces removed) to apply even pressure to the top of the piston. if it doesn't seem to want to go, apply a little more pressure, then back off and try again (making sure it's going in straight). it seemed to bind in many cases and then backing off and applying pressure again would many times get it to slip right in. continue applying pressure until the piston is fully seated into the bore. that's it!

[bimmerboi318]

Yeah I was surprised how hard the pistons moved. Just make sure everything is straight and lubed with brake fluid. I even had a hard time getting mine out. Usually compressed shop air does the trick but mine wouldnt budge.

[cali-ti]

once i got a good seal on the old brake hose/hole, they shot out quite nicely :biggrin:

kinda funny, i bought the caliper grease because it sounded like that should be used for the piston ... then it says right on the tube, NOT to be used on the piston. oh well, used it on the guide pins and i'll lube the other areas that ron stygar showed on his "lets brake it" guide on unofficialbmw.com.