Castrol SRF

[Nocturnal]

Do you need to change the Castrol SRF often? Same say you do, but other say you don't.

Boiling Point:
Castrol SRF: Dry 590ºF (Wet 518ºF)
Motul RBF600: Dry 593ºF (Wet 420ºF)

From what I understand, brake fluid will take in moisture very fast to reach the 3% water content which is the wet boiling point. About 30 days is what I read...

That is why people say Castrol SRF is very good because of the high WET boiling point. But, then everyone say you have to change it often... Why?
If it have a high wet boiling point, shouldn't it be fine even if it is "wet"?

Or will brake fluid continue to take in water until it contain 5% water and so on?

[freakazoid3]

Well my rule off thumb is; the more exoric the brake fluid the more it need changing. When using dot 4.1 in my brakes it feels less firm in use then when using dot 5.1 But it seems the 4.1 remains more stable over a set amount off time.
I change the dot 5.1 at least every 6 months ass it seems to go darker and suck up moisture very quickly and the pedals goes soft sooner. So my advice is not to use the Castrol SRF for to long. I don't use the Castrol stuff myself but all the differnet brands more or less have the same abilities

[frostmotorsport]

i use the motul 600F myself - both in my rally car & GTR. rule of thumb is about 2 years unless you get a leak in the system....

I used SRF in my old rally car - was the absolute nuts! however, it got changed every year or 3000km approx. dunno if that helps.

personally I think SRF is overkill for a road car - even if you intend to track it the odd weekend....

[Nocturnal]

I had the RBF600 in my car for 1 year, 13 month max.

Took it to Lydden Hill and the fluid boil within 2 lap (10 corners)

Just don't know if the SRF will be any better because it still have a high boil point even if it is "wet"

But then I worry about the life of the fluid also. If the SRF will last 2 years, great; but look like 1 year at most for most performance fluid

[P3RV3RT]

Ive been told by a few people the SRF is very good and very expensive. Changing every 6 months is recommended.

I guess you need to keep on top of the fluid if you want the best performance. I will be tracking my 32 quite often so will always be bleeding the brakes/changing fluid.

Now I dont now if this is true but Im sure someone told me that you need to do a complete change of fluid rather than just a bleed. So that would mean its going to cost a fortune using the SRF!

Im on track this Saturday. Im using Halfords special DOT5.1 LOL. The car has R34 Brembo's up front and I hope the get Brembo's fitted to the rear in time. I will give it some stick and see how the brakes get on.

[2rismo]

If it's the difference between enjoying 10% of a trackday or 100% of it, what is a few dollars extra in brake fluid?

[frostmotorsport]

nocturnal - are you sure you "boiled" the fluid, or did you simply suffer brake fade due to excessive heat killing the pads?

Not sure why SRF should be changed so often - it's fully synthetic, and as such should not absorb water - the reason people recommend brake fluid be changed every few years - as normal fluid is hydroscopic (absorbs water)

regarding bleeding etc - yes - you need to buy a litre of SRF, and you can either bleed through each line till you see the new, clear fluid or if you're rich, you can drop the old stuff and start from scratch - but you'll waste a bunch getting the air bubbles out of the lines!

I did my R33 GTR fluid the other month and used about 700+ mls - but I am fussy and rBF600 ain't that expensive....

Also, be aware that you must never mix "grades" of fluid!!!! i.e. 5.0 & 5.1 & 6.0 are VERY different chemically!!! and not necessarily compatible!