Brake Fluid

[exdos]

My light has come on to change the brake fluid, so whilst this job needs to be done, I've got some new Goodridge braided hoses to fit and want to take the opportunity to uprate the brake fluid too. I've got Red Stuff pads with OEM discs.

What is the spec of the standard brake fluid and what fluid spec would others recommend?

I've read that changing from DOT3 or DOT4 (Glycol based) fluids can react with DOT5 fluids and cause corrosion of the brake lines. Therefore, if the standard brake fluid is either DOT3 or DOT4 what procedure needs to be followed to prevent contamination of new DOT5 fluid if you change to DOT5 fluid?

Apparently there are different types of DOT5 fluids, which is the best?

[r80ter]

IMHO, dot 5 should only be used in racing or when you are going to regularly change the fluid. Dot 5 has not got as long a life as dot 3/4 so it will need changing more regularly than if you used 3 or 4. It apparantly degrades the older it gets. Also, only ever use unopened containers when filling a system.

This is what i got told by Silkolene when i was racing anyway. And they didnt say that to me so I bought more, as I got the stuff free anyway!

As for flushing the system out, I use a vacuum pump and pull a good 1/2 litre though each caliper.

[maahny]

I use Castrol SRF in my setup which is DOT4 and have been very happy with it. Have not experienced a sinking pedal yet despite lots of abuse. I thought the brakes were weak before I changed the pads/discs/hoses and fluid.

[r80ter]

further to my initial post, I think mixing of 2 types is not ideal, but when changing a small ammount of the old fluid will remain. This should not be a major issue.

The thing about dot5 corroding brake lines is due to Dot3/4 being able to absorb water, where as dot 5 can not. so any water in the system, (which is almost inevitble) will stay as water thus increasing the chances of corrosion.

IMO, the product that Maahny use, is top quality. I have used the same in the past and rate it.

BTW, My findings are from Bike racing, not Cars, but it all transfers over.

[exdos]

Thanks for the info lads. I shall opt for the Castrol SRF then :D 8)

[c_w]

DOT 5 is a silicone-based brake fluid and not used much and I never see it for sale tbh.

What you want to use (if you're not using the SRF) is DOT 5.1, this is compatible with DOT 3 and 4 but is a higher specification (ie higher boiling point etc). DOT 3/4/5.1 are usually Synthetic-based these days.

[Judge]

Im using ATE Super Blue Racing Fluid in combination with goodridge ss hoses. Very happy with braking performance :D