silicon brake fluid?

[haynes]

Is silicon brake fluid any good, thinking mainly for cars which are not used daily? Particularly on my mates race car we have to change rear wheel cylinders every year or two. Is it possible to bleed through a system with the new fluid or can it only really be used on a brand new brake system which hasnt previously been contaminated with normal fluid? Oh yeah, is it generally any good?

[Neil8p]

I tried it on my trackday car.

I used it when building the car up with all new brakes. I'd heard it can have a bad effect on old seals that have spent their life in normal brake fluid.

The fact it doesn't absorb water (not hydroscopic?) is good, but if there is water in the fluid I suppose it could gather in one place and cause localised corrosion.

In terms of performance, I personally couldn't tell any difference. My brakes were non-servo'd with pads that were too hard so I'd often be on the verge of crapping myself anyway!

The fact it doesn't damage paintwork also appealed to me, but the price didn't.

Track car needs a rebuild, and I'm adding a servo and I'm using normal brake fluid this time.

[Cooperman]

I always use AP600 Racing Fluid in my rally cars. I can boil DOT4 fluid quite easily.
Never tried silicone fluid though. Is it possible to boil it? If so, at what temperature?

[haynes]

Peter, do you have much problem with rear brake cylinders seizing when the car is stood, or do you never let it get that bad! My mates hillclimb car is stood for 6 months and he rarely gets it out during the winter, so its hardly surprising we keep having to replace cylinders. My road car has started pulling to one side probably due to being stood quite a lot over the past couple of months.

[Neil8p]

Not sure if it's possible to boil silicone fluid

Did a quick google and found this

www.apracing.com/car/brakefluid/

I wonder why they don't recommend silicone fluid?

[GreenV8S]

Neil8p said:

I wonder why they don't recommend silicone fluid?

As you said earlier, it doesn't absorb water so the water that naturally gets into the system will collect in nooks and cranies. Then you are knackered in terms of boiling point and internal corrosion.

[jellison]

Try CRF - used on alot of bike - silicone - works for me. Not on th road though - if boiling dot 4 on th road - you should be locked up as a danger to user road users.

[Cooperman]

It's very easy to boil DOT 4 on a tarmac special stage, especially in the mountains. Once it has boiled it goes black and the pedal is very, very spongy. You then have to bleed the entire fluid out and fill with new stuff until it's all clean. Not easy and not recommended. No, it's AP600 race fluid for me in my rally cars and I've never had any problem with it. I bleed the systems out once a year without draining down, just bleed a lot out until the level in the m/cyl is quite low, top up and continue to bleed until low once more, then just top up.

[haynes]

does bleeding / changing the fluid regularly keep the corrosion problems down because your getting rid of the old fluid which would have absorbed moisture?

[Cooperman]

Guess it does as the reason you need to change it is because of its water absorption, which in time will make it more compressable, easier to boil and less effective. Presumably it will cause corrosion as well in the steel components. That's a good reason for getting stainless steel caliper pistons.