DanH said:
I'm curious. Why DOT4? Why not just switch to Mil-H-83282 instead? It was created to address the Mil-H-5606 fire problem, and is completely compatable with 5606 as well as all the existing seals. You can use it in any GA airplane, any time, even to top up 5606.
That said, I also like Viton caliper seals.
Dan Horton
Dan
Dan,
The Viton seals are a great improvement over Buna N, when retaining a mineral oil based brake fluid. While 83282 is an improvement over 5606, it isn't a cure. Your brake rotors can be anywhere from 400 to 1100 degrees Fahrenheit, depending on how hard you have to use the brakes. 83282 has a 450 degree flash point. What good is that against a brake rotor which will likely be hotter than 450 degrees?
Gylcol brake fluids do not burn at all. The Viton caliper seal will help prevent fluid from leaking between the caliper and the piston, but is not the only source of a possible leak. A failure of either the AN822-4D fitting or the AN4 aluminum brake line near the brake rotor could cause a fire. The absolute way to eliminate brake fires is to remove the flammable brake fluid.
The down sides to switching to DOT4 fluids are:
You have to swap out all the Buna N O-rings in the brake parts for EPDM (ethylene propylene) O-rings.
Fluid must be flushed every 2 years
DOT 4 fluid is not compatible with the stock Buna N rubber brake hoses that Vans supplies. Teflon lined stainless steel brake lines like those sold by RV9A owner Chris Heitman's company, must be used. Chris owns Pegasus Auto Racing. I purchased a set of his hoses for my RV8A.
Glycol based fluids can damage older technology paints if they are left on the painted surface for an extended time. This is NOT an issue if the spill is wiped up promptly. It is also a total non issue if you use a urathane or polyurathane paint, such as DuPont Imron, PPG's Concept or Delta, Sherwin Williams Jet Glow and Acra Glow. There are numerous others as well.
The switch to DOT4 is more work, but ensures that there is no possibility for a fluid induced brake fire.
Ask RV6A owner Ed Anderson how exciting a brake fire can be. The choice is yours. Your plan greatly reduces the chance of a fire, mine eliminates it.
Charlie Kuss