Brake Fluid

The Service and Technical Booklet for my 2003 R1150R says to use DOT 4 brake fluid and to change annually. Others have told me that DOT 5.1 brake fluid is better, and only needs to be changed every other year. Who is right?

"we don't need no stinking brakefluid"

Both are right. It is more of who do you believe and/or trust. Unfortunayely there is no difinitive exact time as to when Brake fluid becomes "bad". I havebrake fluid in my truck over 10 years old. Brake fluid in the Harley 3 and 4 years old. And brakefluid in my 96 R1100RT that is 25 months old and it still stops ok. (But it gets flushed out this November)
Max

DOT 4 is a high temp version of DOT 3 brake fluid. I would not put DOT 5 brake fluid in any brake system designed for DOT 3 or DOT 4 unless the service manual says the system seals are compatible with DOT 5.

If you use DOT 5 in a system designed for DOT 3 or DOT 4 it will likely swell the system seals and create numerous brake problems. I know this from first hand experience. The only way to be certain if you really want to use DOT 5, is to totally solvent flush the current system and then install all new seals compatible with DOT 5.

For what you really get out of it, you are far better off to stay with DOT 4 and replace it every few years. Quite honestly,on my 94 R1100RS I ran it with the stock brake fluid for almost ten years with no problems (that I could perceive). A few years back I installed Speedbleeders on the brake calipers and replaced the brake fluid with DOT 4 and have had no problems and have good firm brake feel.

With the Speedbleeders I can flush out and replace the brake fluid on my bike in less than an hour, by myself. It is easy to replace the fluid with only a catch tube and bottle.

Andy, I think you're confusing DOT 5 with 5.1. DOT 5 is silicone based and DOT 5.1 is not. I don't think any maker uses 5 any more. But you're right that DOT 5 will cause havoc in a system not designed for it. DOT 5.1 is a non silicone synthetic. Both DOT 4 and 5.1 are compatable with each other. The most important thing with brake fluid is the boiling point. The higher the better. I've used Motul in all my track and street bikes for years. I flush out the fluid every 12-18 months on my RT. Since the ABS block is under the tank it gets pretty cooked.

Just my $.02

kitze2 said:

Andy, I think you're confusing DOT 5 with 5.1. DOT 5 is silicone based and DOT 5.1 is not. I don't think any maker uses 5 any more. But you're right that DOT 5 will cause havoc in a system not designed for it. DOT 5.1 is a non silicone synthetic. Both DOT 4 and 5.1 are compatable with each other. The most important thing with brake fluid is the boiling point. The higher the better. I've used Motul in all my track and street bikes for years. I flush out the fluid every 12-18 months on my RT. Since the ABS block is under the tank it gets pretty cooked.

Just my $.02

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after seeing this 5.1 fluid i wondered, why not name it 4.1

seems a confusing identifier

Thanks for educating me. That is new to me as I am obviously familiar with the old DOT 5.

For anyone looking for better brake fluid in DOT 3 and DOT 4, do a google search for high-temp brake fluids. There are many choices out there in racing grade high temp brake fluids. You might pay $10 for a pint but if its what you want and compatible with your system, there ya go.

Speedbleeders

Andy, can you speak more on the speedbleeders and a suggestion for where to get? thanks

Purchase directly from Speedbleeders website. Allows for one-person bleeding. Good stuff.