Bruce Banner

I know dot4 is usually used for track, and dot5 for street.
Any benefits to using dot4 on street applications?

Alpinestar03

normal brake fluid is dot-4..

ECX

What is the difference? Never really known... I've always used DOT3

jlhansen

DOT 3 is the old standard. DOT 4 has a higher boiling point, but basically the same spec regarding Hygroscopic properties. DOT 5 is synthetic and non-hygroscopic, but also INCOMPATIBLE with DOT 3/4 and requires a complete flush of the brake system.

That said, I've always wanted to use the stuff in motorcycles, but I was nervous about how it reacts with normal brake parts and any little pockets of old fluid that might stay behind after the flush. I personally would only convert it after a complete overhaul of the system.

jlhansen

Oh, yeah, it also has a tremendously high boiling point, and that's why I wanted it for motorcycles (I've faded bike brakes in the canyons too many times).

JimBlake

DOT 3 and DOT 4 are poly-glycol. DOT 4 has higher boiling points. Both of these will absorb water and gradually reduce the boiling point. The bad thing is that moisture causes the fluid to become more & more corrosive. You deal with that by putting in fresh fluid every year or 2.

DOT 5 is silicone, it will not mix with water. It has high boiling points. It's not always compatible with certain rubber hoses & seals (I don't know whether this includes anything Honda uses).

The bad thing about DOT 5 on the street is it will not mix with water. What that means is, when you get any moisture, it stays separate like -umm- oil and water. Instead of the boiling point dropping to 350F, it drops all the way to 212F. If that moisture gets in the caliper, that's really bad. You can deal with that by flushing your brake fluid before each race.

DOT 5.1 has the high boiling points like DOT 5 but it's poly-glycol like 3 & 4. That's often labeled as DOT 4 because it meets that spec too. I think Valvoline SynPower is an example.

BrakeExpert

I agree with what he said, all true.

Side note: Valvoline SynPower is a fantastic brake fluid, all my friends run it as do a lot of track racers I know. Very effective, and cheap.

ComeOnKip

The biggest thing I know of is DOT 5 is not approved for use with ABS, seeing as how the pulsing action of the ABS foams the ever living **** out of the fluid. I used DOT 5 in my DA9 and ED3 and have had no issues with water or brake fade. IMO tho, pad compound has a much larger part of battling brake fade then the fluid does, cause if your boiling your fluid, either your **** is on point and the fluid is the last weak link or theres something else awry in the set up.

jlhansen

I don't remember ever fading car brakes, but I use the tranny more than the brakes.

With regard to DOT 5 fluid, I've been out of the game too long, I guess. I've never heard of 5.1, but I guess they addressed the incompatibilities. So it's okay to mix it with DOT 3/4 and it's compatible with all normal brake components?