Brake Fluid

[Danman]

I have to bleed my brakes and was goint to changeout the fluid while I was at it. The master cylinder cover says use DOT 4 only (do you realy have to follow that?). I looking to get a few opions on what to use. I have not visited a bike shop to look at what they had on the shelf, but saw some Valveline Synthetic autoparts store that said it was DOT 3 or 4. All the rest of the fluids were DOT 3. Is the valveline any good? Does any one know the difference between the DOT levels of the fluid?

 

[MoO_coW]

Use what it says.

 

[Highbeam]

Use what it calls for. Buying brake fluid is like buying a bolt, if it says grade 8 then you'd better use a grade 8 because it was designed for it. Also, the grade 8 bolt does not need to come from a bike shop. Go down to walmart and buy the cheapest brake fluid that meets the requirement. Brake fluid absorbs water over time and can corrode brake parts and lines from the inside so flushing the fluid is a good idea.

 

[dirt bike dave]

Originally posted by Highbeam
Go down to walmart and buy the cheapest brake fluid that meets the requirement.

I'm going to strongly disagree! If you are hard on your brakes, boiling point is very important. Motul 600 has a 585 degree F boiling point, and mixes with Dot 3, 4, or 5.1 fluids. Yeah, you should still change it every year.

I've boiled cheap fluid on several occassions and besides being unsafe it's a real PITA. Get good fluid - it's well worth the extra few $.

 

[Highbeam]

I was under the impression that one of the things the DOT rating did describe was the boiling point. Perhaps you could find some fancy schmancy brake fluid with a higher boiling point but the specified fluid will be sufficient. How hard are you on your brakes? I hardly use them and I've never experienced fade from boiling. What were you doing to cause your fluid to boil? Is this a case of the stickers that make you go faster?:D

 

[dirt bike dave]

It is true that minimum 'dry' (uncontaminated) and 'wet' (contaminated w/4%water) boiling points must be acheived for each of the DOT #'s. High quality fluids can exceed the minimum boiling points for their DOT #.

I have experienced brake fade due to boiling on 4 occasions with Kawasaki KDX's, twice with original brake fluid (2 different bikes) and twice with fairly fresh DOT 3. Each time was on moutainous, technical trails with long, low speed twisty downhills. One time, the rear caliper had an aftermarket plastic cover that restricted airflow. On another occasion, the rear rotor got warped bouncing off a rock, and the constant drag probably caused the boiling.

I have also seen or heard of several other examples, notably with a buddy and a DR350 on two occasions; once he was riding double.

Once the fluid starts boiling, the brakes will fade easily even after bleeding unless you take a long cooling off period.

Since DOT 3, 4 and 5.1 are compatible (5.0 is NOT), there is no reason not to use the good stuff, IMO. If you have an older bike, it may say DOT 3 on the resrvoir cap, because DOT 4 wasn't around when the bike was made.

Contaminated and old fluid has a lower boiling pont, so an extra safety margin is nice to have and worth a few $, IMO.

 

[Danman]

I have never boiled my fluid, but I don't want to take any chances either. I will proably see want I can find.

thanks for thoughs.

 

[Anssi]

You should have no problems finding DOT4 or DOT5.1 brake fluid, and lets face it, brake fluid is just plain cheap at the quantities we require.

 

[jeb]

Here's a great article on brake fluids. As other's have said, 3, 4, and 5.1 are all compatible and it's pretty cheap stuff. I use Motul 5.1 in all our bikes.

http://www.motocrossactionmag.com/readridingtips.asp?id=106

 

[canucklehead]

Gadzooks! I'm embarassed to actually admit I learned something from MXA!

I need a shower...

Dave