Brake Fluid

[Mnbusa]

Hey all,

Does anyone know if there is an issue using Dot 5.1 brake fluid (Motul) instead of 4?

Is it like most rev'd products where the higher is backward compatible?


Thanks

[Tufbusa]

I'd recommend you stay with dot4. There are issues with using dot5.1. The two don't mix well at all and you'll need to flush all the dot4 from the system and completely clean all the dot4 residue before filling with dot5.1. I believe the dot5.1 was designed for cold weather applications.

Use a good dot4 with a high boiling point. We use Motorex in all the race bikes as well as my street bikes. It's over kill for street use but really good stuff.

[Mnbusa]

Thanks a ton, I appreciate the quick response!!!

[weav808]

I've used it in my GTR, r6, and now my Busa. No problems. Did help eliminate brake fade. Any fluid being replaced will have a noticeable difference for the better.

[BIG GUY]

I agree with what TufBusa said. You should just stay with the DOT4 fluid. It can be somewhat of a long process to get all of the DOT4 fluid out.

[mestona]

I've used it in my GTR, r6, and now my Busa. No problems. Did help eliminate brake fade. Any fluid being replaced will have a noticeable difference for the better.

GTR as in the R35?

[weav808]

R34 V spec

[Mnbusa]

I decided to hold off and will get some Dot 4.

I'll wait until I get a device to fully remove the old oil before giving the 5.1 a try.

Thanks Guys

[Tufbusa]

After a little brush up on brake fluid to refresh my memory, it seems dot 5.1 is a glycol ether-based fluid just like dot3 and dot4. It's the dot5 fluid which has a silicone base that you want to avoid altogether.

Aparently, you can use any of the glycol ether-based fluids while avoiding silicone based fluid. Your busa was designed for dot4 fluids. This means the seals in your system works best with dot4 and will have a longer life with dot4.

The only reason to go to dot5.1 would be if you were racing and changed the fluid often. Apparently, dot5.1 absorbs more water and is a trade off for a higher boiling point which none of us need on the streets.

So my recomendation would be to use dot4. If you do track days go with the highest boiling point you can find. For street use, it really doesn't matter as the minimun requirement for dot4 boiling point is 448 degrees while dot5.1 BP is 518 degrees. You will never reach 448 degrees on the streets and only the very best track day guys will boil the standard dot4. You will definately know if your fluid boils as your brake will become soft and spongy.

You should change your brake fluid once a year at a minimum. Some race guys change the brake fluid after every race. All brake systems will generate water, seems water just magically appears. Even a minute amount of water will lower the boiling point considerably, as much as 1/3! Damn!