gmcjetpilot said:
Why not Mil spec -83282?
Are you guys really using AUTOmotive brake fluids? Really?
Is any one really using DOT 3, 4 or DOT 5 or synthetic auto transmission fluid with success in a RV?
What seal mods do I need to make and why?
I agree the higher flash and flammability of the old mil spec -5606 is not great. I had planned to use the better -83282.
From what charlie kuss, Jconard said leads me to believe that DOT anything in planes is not as desirable as the -83282.
I never considered DOT brake fluid. My concern is compatibility with seals and other "unintended consequences" of using those auto fluids. I know in the past folks who used automotive brake fluids in their RV's had major problems, seals and locked brakes. Probably the older DOT 3 or may be 4.
My plan was and still is to use mil spec -83282. I never had problems with the old seals and -5606 however I know about brake fires, thus I agree higher flash point = goodness. The only down sides of -83282, which are minor in the grand scheme of things, availability, quantity (sold in gallons) and price. The only reason -5606 is still around is because inertia, its been around for probably 40-50 years.
It would be nice if DOT X was equivalent and you could stop by the local car or motorcycle shop and buy a Pint for $3.00, but from what is sounds like -83282 is superior. I am going to stick with aircraft fluids.
Hi George,
Yes we are using DOT 4 or DOT "super 4" (aka DOT 5.1) fluids. You need to swap out all the Nitrile O-rings in the system for identical items made of EDPM (ethylene propylene). You also have to swap out any rubber based brake hoses (Such as Aeroquip 303) for Teflon lined hoses (like the ones used on auto race cars) The Teflon hoses have the added advantages of being lighter, less expensive and having higher pressure ratings. The down side to them is that they are not as flexible as the rubber hoses.
If you don't want to swap out the seals, go with 83282 or synthetic ATF (they are essentially the same fluid). Also swap out the caliper O-ring for one made of 70 Durometer Viton. Nitrile has a service temp ceiling of 250 degrees Fahrenheit, while the Viton is rated to 450 degrees.
The typical failure mode of the Nitrile (aka Buna N) O-rings is that they get stiff and shrink from excess heat. Once this happens, the fluid slowly oozes out, until the day you need to really stomp on the binders to stop. Then those leaky O-rings spray the fluid onto your red hot (1100 degrees +) brake rotors. This is why I believe that "improved fluid" is just an exercise in semantics. When flammable fluid hits a rotor whose temp is over 450 degrees, it won't matter if it 5056 or 83282. Both of them WILL ignite.
I'll agree to disagree regarding the superiority of ANY mineral based oil brake fluid compared to a quality DOT 4 or DOT 5.1 fluid.
To each his own. If you stick with the approved fluids, at least upgrade your caliper O-rings to the above mentioned Viton units. I do have one question to ask you George.
If mineral oil fluids are so great, why does every other type of motorized vehicle (including airliners) use glycol based fluids???? FYI, Skydrol is a glycol based fluid. It's the glycol based fluid from ****!
I've spoken at length with the engineers at Cleveland and they have admitted that the reason they still specify 5056, is because the cost to re-certify with a better fluid is money. The market size doesn't warrant the effort and expense for them.
Just my opinions
Charlie Kuss
PS PS Don pointed out to me [on the next page] that I am in error in my statement above. Skydrol is phosphate ester based, NOT glycol ester.