Ive always used DOT 5 brake fluid in my back brake coz it doesnt boil up. Im fitting a handle bar mounted back brake tonight ive managed to get my hands on DOT 4 fluid will this boil up like DOT 3 or is it not much difference than DOT 5.

 

You cannot mix dot 4 with dot 5, system needs to be totally emptied before changing.

Dot 4 specifies minimum boiling point for fluid. So there is difference in dot 4 fluids, some cheap automotive dot 4 boils easily compared to motorcycle full syntehetic dot4 motul 600. That synthetic motul can take over 100celcius more heat then normal dot4 and it can be mixed up with regular dot4, so it's easier to change then dot5.

dot5 is some silicone **** and it's not good for all the seal types, even thou most brake system can take it.

If you have the system filled with dot5, then use that.

 

Use exactly what the little book that came with the bike says to use. Jacket is right you should never mix fluids and you can seriously screw up your system or worse yourself and bike by useing different fluids.

By the way,, if your messing with dot 4,,,whatever you do, don't spill it. It will eat your paint faster than Aliens blood.

 

i got a question then, i recently boiled my rear brake. so i ended up just bleeding through 2 bottles of dot 4 fluid. should i have bleed it through or drained all the old stuff first and then filled it all with the new ****? and if so, how do i properally drain all the stuff in teh system now? my brake definitally feel different now but i wasnt sure if it was becuase of the new fluid or not.

 

Very true dot 3&4 are compatable but they are not compatable with dot 5, they separate and will destroy brake lines and fittings.

However there is an ABS brake fluid either dot 5.1 or 5.2 that is compatable with dot 3&4. The ABS brake fluid has a much higher boiling point than 3&4. It also last longer in a sealed environment as its suposed to resists moisure. This is what I always use.