its poo 
. in 2004 i was running Dot4 , i gave the scoob more hassle never boiled it once.
incidently Dot 5 is silicone based, if upgrading from Dot 4 we need to use Dot 5.1
The Master Cylinder on my TVR project says "DOT3".....However, I have never seen DOT3 fluid, and have a small stockpile of DOT4...
Can I put DOT4 in this system without totally buggering everything up?
Man at Brakes International told me that DOT 3 was dearer as it had a higher boiling point for racing mainly.
What......... DOT 3 has a LOWER boiling point than DOT4!!!
from what ive just been reading up on the only difference between the two are their boiling points, so i would have thought dot4 should be fine
Miks15...that is pretty much the conclusion I came to...
It seems DOT4 will absorb more moisture than DOT3 however...
scrap what i just said... its to do with the chemical make up aswell (which obviously is what helps to change boiling points) but the seals in your
system might not be compatible. They could give and then youd have no brakes...
So not a good idea to change
dot 3 has a higher boiling point than dot 4 but dot 3 WILL asorb more water than dot 4, but go for dot 5.1 as i believe it is compatable with dot 3
and has the charistics of dot 3 but not absorb much water
I think
in 2003 i was running Dot 3 (cause that what the dealers put in) in the Isle of Man..and it boiled its poo .
in 2004 i was running Dot4 , i gave the scoob more hassle never boiled it once.
incidently Dot 5 is silicone based, if upgrading from Dot 4 we need to use Dot 5.1
quote:
Originally posted by tegwin
The Master Cylinder on my TVR project says "DOT3".....However, I have never seen DOT3 fluid, and have a small stockpile of DOT4...
Can I put DOT4 in this system without totally buggering everything up?
Dot 3 and Dot 4 mineral based are compatible with each other and Dot 5 is completely different silicone. If you are using Dot 5 the system must be completely empty of either of the other types and not all older brake system seals are compatible with Dot 5 silicone based, which also gives more pedal travel as it is more compressible than Dot 3 and Dot 4. As Meany says the Dot 5.1 is compatible with the others but it is not automatically better just because the number is higher.
I can vaguely remember an article on this where dot 5 was not recommended for road cars, just for race cars. The reason was something along the lines
that dot 5 is not hygroscopic, (water not absorbed into the body of the fluid), but the moisture in the air is still drawn into the brake resevoir and
condenses (slowly). Since it is not absorbed in the body of the fluid, it eventually ends up at the lowest part of the system as it's denser than
brake fluid (caliper usually), so when the caliper get hot...... guess the rest (also can cause corrosion. This means its not a problem for a proper
racing cars as the fluid is flushed every race. Unfortunately I can't remember where I read that!
Hugh
Never be tempted to use DOT 5 silicone fluid - been there, done that, spent many hours getting it back out of my car's braking system.
BTW: Is your 'stockpile of DOT 4' unopened? If it has been opened and has been sitting around for a while, then you'd be better off
buying a fresh lot.
Have a look at www.stoptech.com - white papers - brake fluid 1A.