Brake/clutch oil

[krakan]

Hello there, I´m going to change the brake and clutch
fluid, does anybody outthere know if I can use Dot 5:1
brakefluid or if it must be Dot 3 or 4. I could not find
Dot 4 of a decent brand so I bought a 5:1 but now I´m
unsure if it´s usable. Krakan

[fasterdammit]

Should say right on the resevoir; if not the resevoir in the owner's manual if you still have it. Whatever you do - don't "trade up" from one DOT "version" to the next - it's not like software where the next "version number" is better. DOT 3 & 4 tend to be hydroscopic whereas DOT 5 - as a silicate-based fluid - is not. I think the big difference between DOT 3 & 4 is boil-over point? Anyway - although I don't remember which DOT to use, I'm pretty sure it says right on the resevoir. Somebody here will post up shortly, anyway ...

[louis]

Hello

You should never mix DOT 5 with the other one.:thumbdown:

For DOT 3 and 4, no problem

[Apex]

DOT 5.1 is just fine--actually it's your best bet. DOT 3, DOT 4 and DOT 5.1 are all compatible. They are all hydroscopic (sp?) so they absorb water and protect your calipers from corrosion as long as the fluid is changed every 2 years. It gets darker as it absorbs moisture. Silicone-based fluid is labeled DOT 5 (as opposed to DOT 5.1) and should not be used in systems calling for DOT 3, 4 or 5.1. Note that the 3, 4 and 5.1 fluids will attack paint quickly if spilled so keep water around to use on any spills. DOT 5 is used by some manufacturers because it won't eat expensive paint (Harley uses it) and racers use it because it does not absorb moisture which can boil at racing temps. Hope this helps.

Jeff

[Bill]

Dot 5 costs a bit more but I find that as long as you flush out the old fluid well you will have less problems replacing seals in vintage parts. Plus it does not eat paint! I have used dot 5 in my Datsun for 20 years as it has natural rubber seals, (dont know what the duc has) and I dont care to change parts or fluid if it does not leak. When I do a change the old dot 5 it makes a great tire shine, now thats recycling.

[krakan]

I replaced the fluid and flushed it completely with 5:1
and it has performed perfecly with a solid feel in the
brake and clutch hanles. By the way on the top of the
brake and clutch oil (containers??) it is written Dot. 3-5!!
Ithought Dot 5 was a no no?? O well all is fine now.
Krakan

[DesmoDog]

Note that the 3, 4 and 5.1 fluids will attack paint quickly if spilled so keep water around to use on any spills. DOT 5 is used by some manufacturers because it won't eat expensive paint (Harley uses it) and racers use it because it does not absorb moisture which can boil at racing temps.

I'll put on my flame suit here and mention that brake fluid doesn't attack modern paints like it does the older stuff. I know from experience that brake fluid will about instantly attack the paint on a 1972 Triumph (car) but won't touch the paint on a '91 Ducati if you get it off of there relatively quickly. I'm not saying you should let parts soak in it, but if you get a few drops on a late model bike you can wipe it off with a wet rag and no one will be the wiser. I wouldn't try that on your '74 Super Sport though.

One of the problems with silicone based fluid is it's very good at trapping air bubbles, so you have to bleed the system carefully. Don't pump the master cylinder quickly for instance.

Also, according to some people I trust to know these things, some Brembo replacement parts come with a warning not to use silicone fluid with them...