Brake fluid question

[Semuta]

So I've seen it said around here that DOT 5 is not recommended, but I don't recall seeing a reason for this. I recently bought some DOT 5 because that's what the sticker on my bike saidto use, but I'm wondering if I should exchange it for some 4 or whatever . . .

Also, I bought a stainless steel cable, but neither of the F-ing ends spin, nor do the places where they connect . . . that should prove difficult upon installation. (not really a question, just a gripe)

[20774]

Some info here:

http://pweb.jps.net/~snowbum/brakes.htm

[PGlaves]

So I've seen it said around here that DOT 5 is not recommended, but I don't recall seeing a reason for this. I recently bought some DOT 5 because that's what the sticker on my bike saidto use, but I'm wondering if I should exchange it for some 4 or whatever . . .

Also, I bought a stainless steel cable, but neither of the F-ing ends spin, nor do the places where they connect . . . that should prove difficult upon installation. (not really a question, just a gripe)

I can't imagine how a DOT 5 use sticker got on a R90/6. I don't think DOT 5 had even been formulated and DOT specified until later than 1976.

In any event - if you have an essentially stock master cylinder and wheel caliper then you probably ought to return the DOT 5, or throw it out. Or, in the not too distant future you will be looking for a new master cylinder or rebuild kit. The rubber in the system does not like DOT 5.

[bikerfish1100]

I can't imagine how a DOT 5 use sticker got on a R90/6. I don't think DOT 5 had even been formulated and DOT specified until later than 1976.




Paul- I was thinking the exact same thougths, but not having had a /6 in the stable for 25+ years, I didn't want to pontificate upon the specifics. thanx for confirming that my infirm memory is still not dead & gone.

[Semuta]

Well, I don't know . . . there's a silver sticker that says "Use only DOT 5 silicon brake fluid" or some such thing on it . . . guess I'll return that other fluid and get something else. Of course it won't do much good if I can't get this new brake cable on.

[Polarbear]

The 3 and 4 DOT Brake fluids are compatible, but not with DOT5 synthetic brake fluids. The 5 stuff has qualities that require special rubber compounds in the lines manufacturing, that Beemers do NOT have. Use it long and you'll find breakdown in your rubber brake components sooner or later. More likely sooner. The main reason DOT5 was made was for high heat applications in some very high tech autos nowadays, with great braking ability. The 5 can withstand a great deal more heat than 3 and 4 fluids and do well at higher elevations, where heat builds quicker too in brake lines. Boiling brake fluid is a no no! I just recently saw it happeneing in a Toyota Pickup, high in the Sierra Mountains near my home. IT boiled in the Toyota Mini Motothome, coming down a steep grade in Kings Canyon NP, CA....The poor guy was alongside the roadway wondering what to do, as I stopped to ask if he was aok. He was stopped safely, but barely!!! Bikes aer not likely to get this far with heat issues, I would hope:) Randy13233