What are the forums thoughts on 'racing blue' and other performace brake fluid for use in kitcars?

One of the members of the uni motor club has been pushing the merits of said brake fluid and the performace improvments its made to his car. However this is a heavy car thats driven hard on track (audi quatro coupe) and given that they work really very well once blead and that even on a trackday the kitcars brakes dont get as hot as the tintops do after a vigours drive on the road im not sure theres going to be much point?

That said, recently i have been having problem with spongyness. Last time i flushed/rebled it the spongyness went but i didnt get any air out so while reflushing it again is going to be next port of call im not sure this is the cure.
Currently im using bog std halfords fluid bought with a tradecard.


Daniel

I used DOT 5.1 with yellow stuff (277mm discs) on a celica on track, using the brakes HARD.
I reccon it would have faded using DOT4.
The smallish brakes used on the sevens will probally fade with more than 200 hp if used hard on track with DOT4.

Darren

looking at comparable specs doesnt seem that much higher than 5.1 spec
super blue 280 dry 198 wet 5.1 270 and 185, if you are running basic dot4 then either would be an improvement, and the super blue seems to resist moisture unlike the older race fluid

Even fresh DOT4 won't boil at any temperature you are likely to be able to subject it to.

What pulls down the boiling point of brake fluid is the moisture (water) content of the fluid. As a rule of thumb the higher the boiling point of the fluid when new the more hygroscopic it is.

After 6 months a racing or other high boiling point fluid will have a lower boiling point than fresh DOT5.1 or even DOT4. Racing brake fluids are also more much inflammable than normal general service brake fluids.


As a general rule DOT4 is good for 3 years service in the damp UK climate DOT5.1 is good for 2 years service, with a racing fluid I would change it twice a season.

Also don't confuse fluid boiling and brake fade, fluid boiling is one of the causes of "long pedal", long pedal which returns to normal on cooling, brake fade is a fall off in the friction performance of the brake material with increased temperature.

Halfords brake fluid is a bit strange it has a much higher viscosity than normal brake fluids personally I would not use it.

If you have spongey pedal it is 9,999 times out of 10,000 either air trapped in the system or a mechanical problem ie pedal box or its mountings flexing or a caliper problem.

Cortina calipers for example are prone to stuck pistons or pads, if one piston or pad in a caliper is stuck solid you get a slightly spongey pedal which gets steadily worse as the miles are clocked up.

After market calipers mounted on home fabricated brackets will cause a similar problem if the calipers are not mounted 100% true to the disk surface in all axis.

If the steady spring clip has not been fitted to Sierra style floating calipers you get a similar problem.

If Sierra rear calipers are used on Seven type cars they often need to be unbolted and turned so the bleed nipple is uppermost to allow them to be bled through properly . This also applies to some 4 pot alloy calipers

Finally if you have 4 or 6 pot alloy calipers do a web search on caliper flexing for your brand of caliper. All alloy caliper bodies flex more than Sierra or Cortina calipers, a flexing caliper gives spongey brakes.

[Edited on 4/12/09 by britishtrident]