changing brake fluid

Boffington

how easy would it be to change the oil in my disc brakes from dot 4 to dot 5.1?

what are the complications and do i need to worry about cross contamination?

nicklouse

what brakes?

if compatible just the same as a bleed.

ride_whenever

why?

Boffington

avid juicy 3's which are very like the 5's so i'd guess its compatible i'll double check though.

aparently 5.1 oil deals with heat better

omegas

DOT 5.1 can be mixed with DOT 3 and DOT 4, even though it is based on a different chemical and has about half the viscosity.

5.1 has a higher temperature range than 3 and 4. Some say it gives the brake a softer feel being a lower viscosity

nicklouse

omegas wrote:

DOT 5.1 can be mixed with DOT 3 and DOT 4, even though it is based on a different chemical and has about half the viscosity.

Are actually made up from the same base chemicals.

the compressibility of the fluids are about the same,
but yes the viscosities are different. strangely Dot 4 is the most viscous. 1800 Dot 3 1500 and Dot 5.1 860cp. the lower cp. number makes the fluid move faster and make the brakes feel faster.

skyliner

Have you got the wet & dry boiling points of each to hand Nick?
I had figures for 5.1, but I've mislaid them. And I've not been able to find any for dot 3 or 4 in any tech docs I can lay my hands on.
Not urgent, I'm just interested in the difference between them.
Thanks in advance.

Boffington

does the higher temperature range offer enough advantage (in heavy uk conditions, eg 5 min max downhills) to make it worth changing the fluid?

nicklouse

have a look in the teck links sticky there is a link to a page with the infos.

But please be careful as some DOT 4's such as "super 4" from X or Y can have specs that match or are equal to 5.1.

nicklouse

Boffington wrote:

does the higher temperature range offer enough advantage (in heavy uk conditions, eg 5 min max downhills) to make it worth changing the fluid?

what brakes. AS some makers say do not do it.

nicklouse

skyliner
the old Lockheed bottles used to have the BP's on them. Yes the tinnies are kept near the brake fluid. :oops:

skyliner

You are a gentleman, a scholar, and all round snappy dresser sir. Many thanks.
(you can't have your alcohol becoming hygroscopic, that just won't do)

Boffington

avid juicy 3's like i said before they're very similar to the juicy 5's which use 5.1 which made me think it could be done

nicklouse

but why? are you boiling your fluid now?

there is no need. you will need an Avid bleed kit. and you will not notice much if any difference.

Boffington

nah the brakes are fine it was but a whimsical wonderance of a wandering mind-

check me out!