Huxley

I need to do a complete fluid change on the system so what's the best fluid to use?

Dot4/5 synthetic/silicone etc?


Huxley

Hoppy

AP Lockheed Ultra DOT 5.1, from ScoobyMania and others. Avoid silicone. Some racing fluids most not be mixed, and they all need more frequent changing.

Richard.

ChrisB

Silkolene Pro Race from TSL (& ScoobySport IIRC).

Huxley

Need more input!!!! Come on there must be more people on here that can tell me whats the best??


BTTT


Huxley

Hoppy

Hux, I told you once!

You want The Old Croney to comment, but here's the gist of what I found out.

The DOT rating is a measure of water absorbancy, not a heat rating. Racing fluids have higher temperature capability, but lower DOT rating means they have to be changed regularly - not just topped up.

Some racing fluids must never be mixed with other stuff, and they can eat certain metals

Silicon fluid was invented for the US military with zero water absorbancy so that army vehicles kept in storage for long periods were ready for instant action. It has no other virtues.

Pete Croney did a few tests and found some fluids are more compressable than others - important for brake feel. AP Lockheed Ultra was one top fluid, as was some Silkolene and others. The AP stuff is DOT 5.1 and has a high temperature boiling point, hence my recommendation. Very good overall performance.

Pete?

Regards,

Richard.

Huxley

Thanks Hoppy

How much will i need to do a full refill as i need to get rid of all the old fluid.


Huxley

Pete Croney

Nicely put Hoppy

Huxley, the system holds 0.5 litre, but I would put 0.5 a litre through to flush out the old stuff and then your second 0.5 litre to ensure it was full of good stuff.

**TIP** When you have fitted any new lines, pads etc and are ready to start bleeding the fluid, get a long pointed syringe and remove all of the old fluid from the reservoir. Refill with new and you will be sure that you are sending through new fluid, not a mixture of the two. If you don't press the brake pedal during the reservoir fluid swap, you won't get any extra air in the system.

Silkolene Pro Race has a dry boiling point of over 300 degC and a wet boiling of over 190 degC. These are the sort of figures you should be aiming for and make sure any fluid you use is a "24 month" fluid.

Hoppy

Cheers, Pete Your fluid change tips are very helpful.

A few more comments while I'm on...

Silkoline Pro Race sounds like good stuff, and is DOT 4 I believe whereas most race fluids tend to be DOT 3

For the record, AP Lockheed Ultra 5.1 has a dry boiling point of 260 deg C and a wet boil point of 180 deg C, but AP point out that "use of a high temperature fluid should not be used as a substitute for proper brake cooling" and recommend the use of temperature measuring stickers or paint to check heat levels (AP supply both).

One of the racing fluids to be avoided is AP Racing 600. This is designed for very high temperature carbon brake systems, it must not be mixed with other fluids and disolves magnesium Prolly not so clever to spill on your paintwork, then

Best regards,

Richard.

care3

i was thinking of trying automecs stuff
http://www.automec.co.uk/cgi/Silicon...ake_Fluid.html

[Edited by care3 - 5/15/2002 2:49:27 PM]

n1ckr

DOT 3, DOT 4 and DOT 5.1 brake fluids are glycol based compounds that are compatible with one another. DOT 5 brake fluid is silicone based and should never be mixed with DOT 3, DOT 4 or DOT5.1. DOT 3, DOT 4 and DOT 5.1 fluids may damage painted surfaces and DOT 3 and DOT 4 have lower boiling temperatures than DOT 5 (DOT 5.1 has the same boiling point as DOT 5). Furthermore, DOT 3, DOT 4 and DOT 5.1 fluids are "hygroscopic", which means they absorb moisture from the air. This causes the fluid to turn dark, indicating that it is time for the brake fluid to be replaced. DOT 5 fluid will not damage paint, has a boiling temperature in excess of 500ƒ F, and is not hygroscopic.
DOT 5 does NOT absorb water... at all. DOT3 and DOT4 spec. fluids
DO absorb water into solution. (I had this backwards in my head for
years) Absorbing water is a GOOD thing, because if the water vapor (which does get into most fluid systems, especially those that get very hot) settles out of DOT 5 fluid easily and it becomes standing water in the system... that can corrode steel or iron brake system parts.

Also, these silicon based brake fluids (DOT5) are also nearly impossible to bleed. They trap air bubbles (from the instant you pour them in the Master Cylinder) into solution and never have a firm pedal, no matter how many times you flush the system. Also, silicon fluid compresses a certain amount.

http://www.danoland.com/nsxgarage/definitions.html

http://www.swedishbricks.net/700900FAQ/Brake%20Fluid%20Comparison.htm

http://www.vtr.org/maintain/brake-fluids.html

http://www.conecrazy.com/brake.html

[Edited by n1ckr - 5/15/2002 3:16:29 PM]

care3

now im confused?
i thought water absorbtion was a bad thing due to contamination of the fluid lowering the boiling point.

Huxley

Now i'm confused, i have brought some AP 5.1 1ltr,I have now got some I hope that it's the right stuff as I was going on recommendation.

So please don't tell me now that it's no good as I hope it's ok as I have Spent Vast sums of money all of about £8.06 from Raceparts in wallingford as it's local to me "well my mate lives not to far from them and a lunch time trip to pick them up for me

Any way i thought that this is the fluid you get with the AP kits for the scoobs?


Huxley

Steve vRS

Whilst everyone is worrying about their fluid, I've just filled up with Castrol SRF. What horror storries do you all have about this stuff? Or is it the pups parts

Steve

care3

nick
ive read your thread again and i dont see where your coming from:-

DOT3 and DOT4 spec. fluids
DO absorb water into solution. Absorbing water is a GOOD thing, (and dot 5.1)

water absorbtion is a bad thing due to the lowering of the boiling point in turn producing steam causing a spongy pedal and rotting abs units and caliper pistons.thats why you should flush once a year with abs or once every two years without

the water vapor settles out of DOT 5 fluid easily and it becomes standing water in the system... that can corrode steel or iron brake system parts

wheres this water coming from? the fluid is non hygroscopic,thats the whole point

Also, these silicon based brake fluids (DOT5) are also nearly impossible to bleed. They trap air bubbles (from the instant you pour them in the Master Cylinder) into solution and never have a firm pedal,

a good flush may be in order following Petes handy tips
im quite prepared to get my coat on this one just what ive seen after a bit of research

PeeVee

iTrader: (1)

Steve

SRF (IMHO) is the best fluid on the market, we use this in all of our rally cars. (as do most of the world rally & F1 teams) When on stage, the brake discs are glowing a really nice cherry red colour, so you definatly won't be reaching the fluids limits in a road car.

We have tried several fluids over the years and I would re-iterate what has already been said about silicone based fluids, these are a nightmare to bleed & trying to get a firm pedal is bl**dy impossible.

If you can afford to purchase SRF (it's flippin expensive @ circa £40 per litre) then go for it. You won't be disappointed!

Phil


[Edited by Barretts Motorsport - 5/15/2002 8:31:55 PM]