Board logo

Racing brake fluid
madteg - 4/12/09 at 11:33 PM

Is it just me but since i put it in my car my pedal has more feel to it. I mean before it was hard but now its softer but does not boil up like it used to do, is this normal as i thought i had some air let in there but i have bled it over and over

Nash - 4/12/09 at 11:48 PM

Madtag when you say racing brake fluid are you referring to DOT 5 fluid?

Forgive me if I'm telling my granny how to suck eggs but don't mix DOT 4 and 5. 5 is fully synthetic and you have to make sure your seals are not contaminated with 4 and that they capable of taking DOT 5.

If I have the wrong end of the stick I'm sooty and ignore the ramblings of a mad man.

.......... Neil

prawnabie - 5/12/09 at 12:00 AM

You can mix dot 4 and 5, its silicone brake fluid you can't. Silicone is usually a wierd colour, I rememver the comma stuff being purple.

Nash - 5/12/09 at 12:09 AM

No you can mix 4 and 5.1 but not 5. Trust me this was a huge issue in endurance kart racing Rotax MAX and FA's. It actually states it on the bottle.

blakep82 - 5/12/09 at 12:12 AM

quote:
Originally posted by Nash
It actually states it on the bottle.


yep, always read the label

dhutch - 5/12/09 at 12:47 AM

Yes, as from wiki.


DOT 3, DOT 4 and DOT 5.1 are polyethylene glycol-based
Where DOT 5 is silicone-based and not compatable

Hence as i understand it 3/4/5.1 are all comptable, and should be able to be used in any system. Bar really really very old stuff.

However given the specs of Dot 5.1 i dont really see why anyone would need to use Dot5 any more.

I also dont understand why Dot 5 seems safe on seals along with Dot4, unless its a mix of Dot5 and a bit of Dot4 in which case it sint ok?
- Maybe you can get some weird reation between them, but otherwise, if there both ok, that doesnt make sence to me.

I'll stick to dot4!!


Daniel

carpmart - 8/12/09 at 06:20 PM

I now use DOT 5.1 in everything.

As stated by Nash, please be careful as mixing silicone with mineral doesn't work!

britishtrident - 8/12/09 at 07:45 PM

Problem with mixing DOT 5 with DOT5.1or DOT4 or DOT3 is the DOT 5 is not hydroscopic in fact it is water repellant.
If and any water is in the system it will get concentrated in any tradditional Dot 5.1, DOT4 or DOT3 is left in the system, bad news.

Brake fluid is not likely to get anywhere near boiling point unless it contains water.

Best advice is use DOT 5.1 or DOT4 and change it at least every 2 years for DOT5.1 or 3 years for DOT4. Personally I do a partial change every year.