brake caliper seal material

[cleaver racecar engineering]

Hi, Could somebody please tell me what the material used to make the seals in brake calipers is. Thank You.

[DaveW]

Hi, Could somebody please tell me what the material used to make the seals in brake calipers is. Thank You.

EPDM

[romoman]

I saw a website for someone who was offering caliper seals out of something else recently. I can't find the site and don't remember if I was looking at stuff for Brembo, AP, or Alcon calipers. I think it was a caliper rebuilder for tintops, but I can't remember who it was.

[Tigaman]

<edited>

[tstrong]

As Dave mentions EPDM is generally a very good choice. Viton is usually suitable as we'll. I would stay away from Buna-N/nitrile as it is attacked by many glycol based brake fluids and will not last nearly as long as EPDM.

[Tigaman]

Ok. Thanks. Comes from working with old Italian cars...

According to this compatibility table, it checks out ok...

http://danamark.com/files/Chemical_Compatibility.pdf

[DaveW]

As Dave mentions EPDM is generally a very good choice. Viton is usually suitable as we'll. I would stay away from Buna-N/nitrile as it is attacked by many glycol based brake fluids and will not last nearly as long as EPDM.

In 2010 I did a swell test with Viton in Castrol LMA because I wondered if it might be OK. It had way too much swell, and, IMO, will not work.
------------------------------------------------------------
Swell test of Viton O-rings in Castrol LMA brake fluid

Test...........................% volume swell
210F soak for 24 hr...............34.7

210F soak for 24 hr
+ 75F soak for 72 hr.............78.2
-------------------------------------------------------------

IMO, most o-ring materials, except EPDM, have a problem with brake fluids.

[DaveW]

There are different cure methods for EPDM. The normal one gives a service limit of ~212F. There is another cure method (Peroxide) that gives a service limit of ~300F.

IMO, the 212F limit is not high enough, and the seals will take a set and leak in our high-temperature applications.

[Tigaman]

Thanks, Dave. Great info.

[Gary Slahor]

Also be carfeull if you're getting someone to make caliper seals to your specs.
I tried to get some EPDM seals made for racing brake calipers and when they found out what the application was they refused to do business with me
They quoted liability issues !!

[R. Pare]

Buna N is not used for caliper seals since it is totally incompatible with brake fluids. The 'common" material is EPDM, which is excellent for the majority of uses, and then Viton, used for the most extreme high-temperature applications, but the brake fluid compatibility has to be verified - different formulations of Viton will react differently to the fluid.

[R. Pare]

Parker also sells square seals, so you can also check with them for availability in your size. However, you will also want to check the exact cross section dimensions - not all manufacturers make their cross sections the same for the supposed same size seal.

[Modo]

Probably rope dipped in brake fluid for the British calipers .......... LOL cudn't resist .....carry on folks