DOT3 or DOT4 brake fluid?

[85 250sx]

Well i had to replace my front brake master cylinder on my 86 250r atc and replaced it with one from a 450r. well while i was waiting on the 450r parts to come in i looked on the old 250r mastercylinder cover and it said use only DOT3 or 4 brake fluid. so i went to the store and bought the first one i saw witch was a DOT3. well now that the 450r parts came in the 450r master cylinder says use only DOT4 brake fluid. I was wondering what the differance was between the DOT3 and 4 was and i if i could still use the DOT 3 brake fluid? thanks

[hondatrikesrule22]

I am having the same problem. I have a Husqvarna 50 that has front disc brakes. It saysto use only DOT 4, so I used DOT3, and I have bled the crap out of them, and still can't get them to work. I guess the DOT 4 fluid is thicker?

[Maine_Triker]

DOT 4 is for heavy equitment and the like, DOT 3 is for atvs. I think, thats what the auto parts guy told me.

[85 250sx]

im wondering if only the brake calipers on the 450rs need DOT4 or does the master cylinder need it as well because every thing on the trike is the same exept the master cylinder so if the 250r calipers can use DOT3 maybe i can still use it??

[yater]

Either will work. In my dirtbikes, I HAVE to run dot 4 or I get brake fade. Dot 4 has a higher boiling point than DOT 3 and will resist fade to higher temps (harder riding). The difference between DOT 3 & DOT4 has nothing to do with the poor bleeding job. Try backbleeding. It takes 3 minutes and works every time

[twgranger]

I have used both and i can't tell a diffrence in them.

[85 250sx]

Either will work. In my dirtbikes, I HAVE to run dot 4 or I get brake fade. Dot 4 has a higher boiling point than DOT 3 and will resist fade to higher temps (harder riding). The difference between DOT 3 & DOT4 has nothing to do with the poor bleeding job. Try backbleeding. It takes 3 minutes and works every time

What do you mean by brake fade?

[yater]

When I ride REALLY hard and go between accelerating/braking for 30minutes or so at a time (as in a mx race), the brake lever will feel spongy and the brake becomes ineffective until it cools a little. I have experienced this only with DOT 3 fluid and NEVER on a trike. That's why I said you'll be ok. You have to really ride the brakes hard to get them to fade.

[grundlegrabber]

Dot 4 is rated at a higher boiling piont than Dot 3. The fluids are both made of the same base. Under heavy and frequent braking, such as in racing conditions, Dot4 must be used to reduce the chance of brake fade. Brake fade is when the fluid behind the caliper piston heats up to its boiling point, causing the hydraulic system to become ineffective. Bottom line is either fluid can be used. I recommend Dot 4, as I have in the past experienced some minor problems with dot3 when riding real hard. DO NOT under any circumstances use Dot 5. Dot 5 is a silicone based fluid that is not hydroscopic (meaning the fluid does not absorb water). Normal brake fluid absorbs moisture while dot 5 causes any moisture to separate and lay behind the caliper pistons, causing corrosion problems. Brake fluid should be drained and the brake system flushed out every few years to get rid of built up moisture and keep the system clean and free of corrosion. Failure to do this eventually results in siezed calipers and leaking master cylinders. Also, you should never leave a container of brake fluid or your master cylinder lid open for more than a few minutes, as the fluid will absorb water much more rapidly than you think. Hope this helps! :beer