Synthetic Brake Fluid

colobeamer · 03-30-2011, 08:38 PM

Anyone change their brake fluid to synthetic - perhaps Motul RFF 600 Racing? BMW service department warns against synthetic, says this will attack the seals and destroy the master cylinder. Why is that?

**1000RR** · 03-30-2011, 08:48 PM

If I recall correctly, I think the owner's manual recommends DOT 4 brake fluid.

The Motul RBF600 is DOT 4. That's what I changed mine out to.

Toynut · 03-30-2011, 10:47 PM

Stay away from DOT 5 brake fluid (silicone based), particularly on ABS equipped vehicles that are ridden in the street.
Dot 5.1 will give you the extra high temp rating that your looking for and work just fine in the brake and clutch circuits, both on the road and track.

kevin_stevens · 03-30-2011, 11:31 PM

Synthetic != DOT 5

KeS

colobeamer · 03-30-2011, 11:32 PM

Greetings - thank you for the prompt response - may I ask how many miles you have since the change to synthetic? Motul RBF 600 is, indeed, DOT 4. & this BMW service manager has a solid racing background & given me good advice on my first K Bike, however, on this occasion I need to confirm his judgement with someone like YOU!

If you ever find yourself in the Denver area, let me introduce you to Golden Gate and Coal Creek Canyons - they will fundamentally change the quality of your life, my brother.

kevin_stevens · 03-31-2011, 01:45 AM

No idea what you're talking about, but I've been using Valvoline synthetic brake fluid in motorcycles and cars calling for DOT3 and DOT4 for ten years or more. Part of the DOT spec is for interoperability, and there's nothing magic about "synthetic" vs "non-synthetic" oil bases.

My criteria for brake fluid is that it has a relatively high wet boiling point and is cheap in small containers. If I were a racer I'd have different criteria. But in any case, I suspect anyone who told you it would eat your seals was trying to shortcut any chance that you would put silicone DOT5 in your brake system.

The owners manual only specifies DOT4, so that's all they can hold you to.

KeS

DrIoannis · 03-31-2011, 02:59 AM

You will be fine with RBF 600 or 660.I use Castro SRF which is a DOT 4 but superior to any brake fluid.The only draw back is that you need to change it every 18 months (I do it every year).
http://www.opieoils.co.uk/p-740-cast...ake-fluid.aspx

Dan Kyle · 03-31-2011, 10:42 AM

I also use the Castrol SRF.
But I have removed the ABS from both of our bikes.

The recommended fluid if you are retaining the ABS is Dot 5.1.
I use the Motul.

Dot 5.1 is a misleading name, it is similar to a dot 4, BUT, the fluid is thinner allowing the ABS to work faster.

The ABS is just a valve that bleeds off fluid, the thinner the fluid the faster it works.

**1000RR** · 03-31-2011, 11:13 AM

That's for the further info Dan. I'll have to check out the Motul 5.1 next go around.

kevin_stevens · 03-31-2011, 12:10 PM

Quote:

Originally Posted by Dan Kyle

I also use the Castrol SRF.
But I have removed the ABS from both of our bikes.

The recommended fluid if you are retaining the ABS is Dot 5.1.
I use the Motul.

Dot 5.1 is a misleading name, it is similar to a dot 4, BUT, the fluid is thinner allowing the ABS to work faster.

The ABS is just a valve that bleeds off fluid, the thinner the fluid the faster it works.

Where's that recommendation from, Dan? Owner's manual just says DOT4.

KeS