I see this new DOT 5.1 fluid floating around the stores, claiming to be DOT 3&4 compatible (I understand DOT 5 is not). Has anybody tried it, or would recommend it? How does it feel?

 

Dot 5.1 is compatible, Dot 5 is not. I've have not used Dot 5.1 yet, but I do run ATE super blue racing Dot 4 in everything I own. I think it works better that regular Dot 4. I seem to have better brake response with no fade.

 

DOT5 is silicone based. its a completely different kind of hydraulic fluid. that's why it's not dot3,dot4, or dot5.1 compatible. they are polyethylene glycol based


if you're on the streets, i highly doubt you'd ever need 5.1. it has a way higher boiling point, which is really nice if you're racing. but if it's just street duty, and you are on a budget, just stick with the dot4 stuff. dot5.1 would last longer though (because the boiling point drops off as water is accumulated to the fluid and the BP for 5.1 starts higher), but not long enough to ever justify how expensive it is.



btw, dot5 doesn't eat your paint. ergo, lots of harleys use it. so, you'll sometimes see a motorcycle on dot5 bottles or a shop manager will say "i dont know, but a lot of bike guys use dot5." don't you use it. your piston seals in the calipers aren't meant for the silicone stuff,

 

The brake system can use dot5, and the seals will be fine. Where you run into seal problems is when you mix dot 3/4 with 5. When they combine, the fluid turns to acid and eats the seals and other brake parts. To switch to dot 5, you either need to flush the system completely free of dot 4 or start with a virgin system. It's usually more hassle than its worth.

 

All excellent information; I love this forum. I only race like twice a year, and nothing beyond goofing around, so I think I'll stick with the Super Blue.

 

Loos like according to ATE, Super Blue EXCEEDS DOT 5.1 standards:

"ATE® Super Blue and TYP 200 (DOT 4) High Performance Brake Fluids have a dry boiling point of 536F and a wet boiling point of 396F."


DOT Specs:

Dry boiling point Wet boiling point
DOT 3 205 °C (401 °F) 140 °C (284 °F)
DOT 4 230 °C (446 °F) 155 °C (311 °F)
DOT 5 260 °C (500 °F) 180 °C (356 °F)
DOT 5.1 270 °C (518 °F) 190 °C (374 °F)

 

Stuff is the bomb. Drain the reservoir, fill it with blue, and bleed the brakes until it comes out blue.