Brake upgrades

o-ringAs the years go by, I’m always looking for small upgrades to make the plane safer. If you do a bit of research on the internet forums you can find much information about brake problems and even some brake fires. Of course there are also thousands of planes that have had no problems at all. Here’s a little snip of a recent post for some solutions.

Two other easy upgrades. First install caliper piston o-rings with a higher temperature rating. Nitrile is only good for about 275F, while fluorocarbon (Viton) o-rings hang in there to 450F. A Cleveland engineer told me the only reasons they stick with nitrile are (1) certification, and (2) better sealing at very low (like -50F)temperatures. Unless you live in the Arctic, Viton is the way to go. Nobody in the brake world still uses nitrile except us goofy airplane people.

The second painless upgrade is a switch to MIL-H-83282 fluid. It was developed to replace good ‘ole MIL-H-5606 for a very good reason; fire resistance. The flash point of MIL-H-5606 is 220F vs 460F for Mil-H-83282, and 83282 is self-extinguishing. Replacing 5606 with 83282 is no trouble; they are completely compatable. Drain one, pour in the other. Mil-H-5606 isn’t useless. It retains its low viscosity at -40F, so if you fly your RV at 30,000 feet you’ll be happy to know the brakes will work

Consider the fluid specs in light of the failure temperature of nitrile seals. Get your stock brakes hot, 275F or above, and you start dumping 5606 brake fluid with a flash point of 220F on brake parts already well above that temp, all in the nice calm air inside a wheel pant. Can you say “brake fire”?

I decided to order up some parts and add this to my winter project list for this year’s anual inspection. I got the o-rings from o-rings Inc and the new brake fluid from ACI Lubes on the internet.

218 V75 (1.234 X 0.139) is the o-ring to get

It should be great fun draining the brake fluid out, pumping new in, etc… but once it’s finished will provide some extra safety margin in case it’s needed.

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