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I'm in the process of refurbishing my calipers and i've ran into an issue. I purchased a full refurb kit which comes with 36mm diameter pistons. I have just torn mine down and noticed I have 2x 34mm and 2x 38mm pistons. I cant seem to find a kit that has the two different sizes. From the outside they look like the standard 4 pot sumitomo's you see in all of the rebuild videos.
My FD's a 97 RS edition if that makes a difference.
Can anybody point me toward the pistons and seals I need?
Thanks
Update: Can anybody confirm F12433651 and F13333651 are the variable piston sizes?
Last edited by Mark Bradley; Nov 17, 2024 at 06:16 AM.
I'd just reuse the pistons that you removed from your calipers. If they're corroded, just use some valve grinding compound / jeweler's polish and knock it off.
At least that's exactly what I did, and my brakes work flawlessly.
I buy stock brake seals from Ray.
the "17in" calipers are different from the standard calipers. they are wider and the pistons are 2 different sizes as you have discovered. the pistons are reusable so long as they are clean and from major pitting. they are pretty robust. you have the 17-?YA calipers lol
After the bead blasting/stripping I get you're concerned about the cruddy appearance of the piston faces and the area where the boots are retained - don't be.......new pistons will be exactly the same at first pad change. You've only got to worry about the sides (and the seal groove in the caliper body). I generally used fine scothbrite and metho to clean seal residue and whatnot from pistons.
