Just looking on Opie oils for some brake fluid. The ones it recommends for the car are dot 4 which I guess is perfectly fine, but I just thought I'd gather oppinion here before I buy. The 'dot' rating is the maximum operating temperature is it?

Whatevers in there at the moment seems ok (whatever honda use I guess), I've never had any brake fade on track (red stuff pads, oem disks), but maybe it's worth having a more temperature tolerant fluid in there? Though I'm not sure if there's anything in a dot 5.1 fluid that renders it incompatible with the s2k brakes?

Oh, and how much do you need for a full fluid change?


edit: ok, I'm extra confused now, I've found 'dot 4' fluid that exceeds dot 5.1 spec, and has a higher boiling point that a few of the dot 5.1's I've looked at. So what does the 'dot' rating mean?

example

 

Hi MIP,

Some stuff here might help:

https://www.s2ki.com/search/forums?f...ry=brake+fluid

DOT numbers are boiling points of the fluid, the higher the number the higher the boiling point. People go for higher numbers for hard track use. There are some more complexities than that, but it's a basic explaination.

 

The Motul RBF600 is widely used by track day regulars. It's a bit more expensive than the regular stuff, but seems to take the punishment well enough in my experience with it.

Not that I really had any problems with the OEM stuff, mind you.

 

Okie doke, RBF600 it is. Cheers

 

Don't go for DOT 5 though!!! I think its silicone based or something so will destroy most of your braking components. Its 4 or 5.1.

 

Yes stear clear of Dot5, though you will be hard pushed to find it these days. As far as I can tell the only people that use it are museums and the US Military.

As above, Dot4 or Dot5.1. The motul RBF600 is known as a super dot4.

Cheers

Guy

 

dot5 is also lighter (i cant remember the correct word for it!) than water. thus the water will sink to the lowest point of your brakes and cause issues!
obivously when bleeding to eliminate water, then the bleed nipple also has to be at the lowest point of the calipers.

 

None of that is correct.

Actually its hygroscopic and suspends water molecules.
You wont get puddles of water in brake fluid so no idea where you got that idea.

And since the water is always in suspension, the only required place for bleed nipples is at the top of the calipers.
Surprisingly that is where you find them.
As air rises to the top of the units.

S

 

internet BS obviously!!!

i stand corrected

 

Im no chemist but to be more accurate I think we would say that water is misceable with brake fluid.
Brake fluid DOT 4/5.1 etc being mainly a type of Glycol base.
Another type of Glycol is what your antifreeze mostly comprises, and explains why it doesn't all sit at the top of your radiator.

HTH.