Volume of brake fluid

[Kurt in S.A.]

By not absorbing water, DOT 5 lets the moisture condense out where it can attack the inside of the master cylinder. DOT 5.1 is glycol based and would work, but it's not really buying you that much for everyday use. Stick with DOT 3/4...it's proven in our bikes.

Kurt in S.A.

[daz]

I'm with barryh. There is no mess with using gravity. I end up squirting brake fluid all over the garage using a syringe!

[barryh]

DOT 5.1 is glycol based and would work, but it's not really buying you that much for everyday use. Stick with DOT 3/4...it's proven in our bikes.

I agree. DOT 5.1 has a higher temperature rating but it's also more hygroscopic than DOT 4 so will need to be changed more often. We have no need for the higher performance of DOT 5.1 on an airhead so the net result for all practical purposes is that it's inferior to DOT 4.

[melville]

Why didn't Dot 5 (silicone) brake fluid gain acceptance? It's not corrosive, doesn't absorb water, seems to me it should be a better product for street bikes.

Harley specified it for years. But not lately--it's apparently incompatible with ABS.

There is now a DOT 5.1, but it's not a silicone fluid.