o-rings that seal caliper halves

850oldschool · Post by **850oldschool** » 08 Mar 2020, 13:22

Any sources?

No number on parts diagrams because, obviously they intended that you'd replace the whole unit with a rebuild. But splitting the calipers makes the cleaning and inspection process drastically easier and I can't imagine any caliper rebuilding shop doing the job without splitting them, so the rebuilders are sourcing them from somewhere.

I'm guessing these are the same on a broad range of Ate calipers furnished as OEM on Porsche, Benz, etc.

The material of choice for brake seals and o-rings appears to be EPDM, but a square cut EDPM o-ring is a pretty exotic item, not to be found at Mcmaster-Carr. They do have buna in square cut and EPDM in standard round cross section.

jeffsws · Post by **jeffsws** » 08 Mar 2020, 15:07

I would love to know this as well. That and the torque spec for the four bolts.

Post by **abscate** » 08 Mar 2020, 17:35

You can find square cut orings in any material

Just use a standard torque for the size of fastener that holds the caliper together.

I broke open a rear caliper and found a round cross section oring

850oldschool · Post by **850oldschool** » 09 Mar 2020, 09:37

Maybe you could drop us a hint on where you usually shop for "any material" o-rings?

Post by **abscate** » 09 Mar 2020, 11:16

I got some speciality Teflon o rings for a project from a firm in WA called...

The Oring Store

Www.theoringstore.com

850oldschool · Post by **850oldschool** » 12 Apr 2020, 21:22

My best guess on the size of these o-rings is that the inside diameter is 6mm(.236"), the outside diameter is 11mm(.433"), and the thickness is 3mm(.118"). The pocket machined in the caliper measured .420" inside diameter and .100" deep. The .013" interference fit would grip them nicely and hold them in place for easy assembly, while the .018" crush fit would be about right for a good seal.

I haven't been able to find these yet. If The O-ring Store has them they aren't listed on their website. I filled out their contact form.

Post by **RickHaleParker** » 12 Apr 2020, 22:26

850oldschool wrote: ↑09 Mar 2020, 09:37 Maybe you could drop us a hint on where you usually shop for "any material" o-rings?

Just looked at the Advance Auto parts website. They have Exact Fit brake caliper rebuild kits for the 1995 850.

850oldschool · Post by **850oldschool** » 12 Apr 2020, 22:33

Yes, I already have the Ate brand kit, but the o-rings which seal the caliper halves are never included in any rebuild kit. The old ones were sealing OK, so maybe I'll just put them back in.

jeffsws · Post by **jeffsws** » 13 Apr 2020, 02:32

So you have split the caliper then? Could you measure the o-ring for us? I could have sworn there was a thread here somewhere with a picture of the exact measurement, but have been unable to find it. It is possible it was on another forum, however.

Post by **abscate** » 13 Apr 2020, 06:10

I measured it onrears and a uK poster sourced internal rebuild kits for us. Not available here

I think I indexed it under the rear caliper part number