how to refurbish front calipers

[bunnysZ]

going to upgrade from single to twin disc this winter.
so want to refurbish the calipers
have split them, going to change rubber bits etc.

but how do you check the pistons work ok.
how do you get them out , clean them and put them back.

[tlc]

I`m in the process of doing mine Paul.

Compressed air can get the pistons out easily enough or just pump them with fluid until they pop out.

I`m investigating vapour blasting and the thought occured to me that Doug Cox may be able to help ? He would also be able to paint them.

[Steve S]

Bunny and Chris,restoring them is not a hard job to do but a couple of things to watch out that I found when doing mine. Watch paint coverage on caliper jointing faces,mine was powder coated and when assembled found the caliper flexed at the joint due to the coating,sanding down fixed it but a point to note.
Also be careful of the small o rings when re assembling they break easily if too dry, a little lube always helps.

[Pigford]

I found best way to remove calipers is do it before disconnecting hoses or draining fluid

Just remove caliper from forks, take pads out then squeeze lever

If you've got modern multi-piston calipers, they all come out at different rates (some stick) - so, you get the easy ones 3/4 out then hold them in place with a good zip-tie, and keep pumping, then the tighter ones move out. If you don't hold the easy ones, once a piston is free, the others obviously won't move anymore

[bunnysZ]

once the piston is out is it just a matter of cleaning up and pushing back into place again.

[Steve Cooke]

It's a simple job, I use compressed air to remove the pistons entering via the bleed nipple hole, make sure you stuff a bit of rag inside the caliper as the piston can pop out with a bit of force. After cleaning in the parts washer and blowing through with an air line I masked off the inside faces and sand blasted them back to raw aluminium before giving them to my mate for coating,I've had them two packed which is not durable enough for the brake fluid, powdercoated and stove enamelled which are both durable, the best finish to me by a long way was the stove enamel in satin black. Assemble with a bit of lube to the rubbers and the two bolts to allow them to slide, job done.

[wilsonsjw11]

Bunny
Once the piston is removed you will have to inspect it,they are usually pitted and will have to be replaced.When removing the piston seal keeper ring be sure to prise it out carefully as you do not get a new one with the replacement seal this can be done with 2 large flat blade screwdrivers.
You will need some red brake grease for the rebuild.
As an alternative to painting,I had my 2 calipers blasted to remove paint,vapour blasted on the internal side and then satin powder coated(very thin coat) all done by Griffs reality M/Cs in Bristol.I have painted them in the past and they chip and are also attacked by the brake fluid when bleeding.I will post a couple of pics of my restored calipers later then you can make your own mind up.
One last thing when rebuilding the calipers smear copper grease on the 2 allen bolts where the caliper is designed to slide with the action of braking.
Regards
Steve

[floydsz1]

I had my calipers powder coated in black at http://www.triple-s.co.uk/
when they came back the mating surface's where not coated etc (they mask them off) so went together with no problems.

[Ginger Bear]

As wilsonsjw11 say's RED BRAKE GREASE. Apply this behind the seals, especially the dust seal. It will stop the bare alloy corroding & expanding, which is effectively what seizes the pistons.

[wilsonsjw11]

Bunny
A couple of pics as promised of satin p/c finish to caliper
Regards
Steve

[GEZ635]

All good advice but remember they were never powder coated originally so it just depends how original you want your bike. Plus, paint is easier to touch up should you scratch or chip it, powder coat is a bit harder to work with should it chip. As for blasting, I soda blast my metal/Aluminium to remove paint.I have shown a few bits to some of the boys on here and they are converted! I can post a picture of a brake caliper carrier bracket if you want to see how it looks after soda blasting. It removes all paint,leaves a great natural finish and is a little less harsh than Vapour blasting with no grit to worry about.