Brake seals - '93) - Venture Rider

Hello everyone. I’m part of a Baja team from Brazil and I am having some problems on the design of our new master cylinder. In the last prototype we used PTFE o’rings to seal the brake fluid. But the lifetime of the o’ring is way too low, like 4h in the maximum. I though in use some U-ring’s but I don’t have sure if this change can improve the lifetime. I saw that commercial master cylinders use piston cup and some kind of u-ring.
Usually the pressure it is around 8 Mpa ( Psi), but it can be higher since it is used in racing conditions. We use an 11.5mm bore diameter, but it is changeable to any size avaible of seal. The master cylinder is made of aluminum.
There is any better type of seal that I can use? Do you now any book that can give me more information about it?
Oh, sorry, i wrote wrong the material. Yes, we actually use EPDM o'rings like TugboatEng said. About buy it ou design it. Well, since it is a racing competition I think is good to design our system, first because we reduce mass but also because we have a lot of more points to talk about in the presentation. I agree that the issues may not compesated all the work we have, but for now, we are taking the risks.

Obs: We also design our calipers, but we buy a motorcycle caliper seal ( because it is avaiable ), so we dont have problems with this one.
Obs : Sorry for any english mistakes.

for now, we are taking the risks.

It is not "WE" who are taking the risks, it is the poor schmuck who volunteers to drive the vehicle.

Do not let your hubris and your eagerness to have something to discuss put that person's life in peril.

Buy some nice, shiny 'racing' brake parts, analyze the hell out of them, and test them to failure in a static test rig. Then do the same for your homebrew stuff before you start thinking you can do better. You will probably want to race with the commercial parts, and you will be able to explain why in your presentation.

Take some time to review the development of disc brakes, taking special note of how complex the early ones were. Later ones are much simpler, but there are subtleties that you might miss, e.g. square section seals and subtly tapered groove faces on caliper pistons to provide retraction.






Mike Halloran
Pembroke Pines, FL, USA