Brake Fluid

[jp7]

Sorry for this old chestnut again but i couldn't find the posts from a few months back. I'm upgrading to green stuff pads and thought it would be a good time to change the fluid. Can anyone recommend a good one. Cheers

[John Whyman]

If you are a racing man get a second opinion but for a road car if you are prepared to completely renew your pipe system and flush out all signs of old fluid, then fine, but I would stick to whatever is currently in their at the moment (they don't mix). By all means change it, which you should do anyway once every 2 years or so as it becomes contaminated with air and water, and Caterham don't recommend some types ( Check with Tech). Any DOT 4 standard is O.K.(if that is what is in there) as they all conform to a tight tolerance/standard.

 

 

 

Happy Motoring. thumbsup.gif C7 WJW.

 

Edited by - John Whyman on 2 Jun 2001 20:13:34

[captain chaos]

If it's a car you've not long acquired, how can you tell what's in the system? I know the silicone fluids are easy to check but what about the other standards?

Can't I just continue using a DOT 4 of a different brand?

 

Renewing pipes seems a bit drastic if you're just changing fluids...is it really that crucial to purge the system so completely?

[John Whyman]

This is a personal opinion,(borne out of experience) but I take the view that your brakes and your tyres are your life, so don't mess with them. Fluid will contaminate any carrier, like a pipe, and is very difficult to purge completely if you are considering changing to a silicone product ( which is not recommended by Caterham) or vice versa. Any brand of DOT 4 standard is O.K. as they are all made to the same BS (stay with the same if possible). I agree it is not always easy to see what you've got so I always flush through, change once a year, and refill with recommended product or same BS equivalent. Not necessary to change tubes, but check over all joints, connections and bends thoroughly.

 

FYI, the 1700x/f I acquired from Caterham had so much crap in the fluid tank it was virtually black and the pedal was spongy. A flush through and fill with Girling DOT 4 and all is fine with good firm pedal.

 

 

 

 

Happy Motoring. thumbsup.gif C7 WJW.

[jp7]

Cheers for the replies. I've had the car from new in 95. In 98 I asked for the fluid to be changed during a service at Caterham, but to tell the truth I'm not sure that it was. During last year i did a couple of trackdays and the brakes were crap. After each rest there was absolutely nothing there until I'd pumped up the pedal a couple of times, and even then under braking it didn't inspire confidence. I almost ran into the back of an R500 at Brands as he braked for one of the corners! So I thought i've got to do something about this.

The car came with DOT4 fluid so thats what I'll replace it with, however a friend of mine suggested Halfords 5.1,Is this synthetic? If it is would flushing the system thoroughly be OK?

[Luke Beaumont]

As yet another Comma brainwashee I've gone for their DOT5.1 stuff for my new 7. Just a few quid/litre more than DOT4 so I thought it worth a try. From the Comma website:

 

"DOT 5.1 Synthetic Brake Fluid

Highest quality brake fluid - formulated for todays high performance vehicles.

Minimum wet boiling point of 180ºc - ideal for all ABS systems.

Non-silicone based, can be mixed safely with DOT 3 & DOT 4 Fluids."

 

 

Never had to change fluid before, but wouldn't it be possible to use an Eezibleed to blow the old fluid out with air before filling from scratch with new?

[AMMO]

Andy

 

I would use DOT4. Not had much luck with DOT 5 synthetic as is not compatible with some types of seals (Brembo in particular). It's only good attribute is that it doesn't strip paint.

 

Not so worried about flushing the system out as most fluids are meant to be compatible with whatever happens to be in there. Just bleed it through until it comes out clean.

 

I agree with John about not taking any risks with brakes as your life depends on it. Make sure all the air is out. One good trick is to push the pads back as this will make any air that has worked its way back up the hose and trapped near the master cylinder come out into the reservoir. Make sure the reservoir is not full to the top or brake fluid will go all over your nice paintwork.

 

For racing and track days 550 or 600 degree AP brake fluid or Castrol SRF. If the pads transfer too much heat even these specialist fluids will give up the ghost. In this case I've not found a better pad material than Performance Friction. Makes all brake fluid problems fade away!

 

Don't know if anyone uses these pads on Caterhams (or even if they are available) as most recommendations seem to be towards EBC products.

 

Hope this is of use.

 

 

AMMO

[Chelspeed]

People are confusing Dot 5 and Dot 5.1. This is what I understand:

 

Dot 5 is the silicon stuff and to change you need to fully purge, change seals etc etc. After all that it's a little bit compressible so pedal pressure is allegedly not so good. Good for show cars that get driven once a year as it doesn't get contaminated with water. Not good for fast road or race cars.

 

Dot 5.1 is state of the art "normal" brake fluid. You don't need to purge anything else out (unless you've been suckered into silicon in the past...) as it mixes OK.

[Luke Beaumont]

That's my understanding too Chelspeed. I don't know if DOT5.1 makes that much difference to all but extreme Caterham use, but if nothing else its wet boiling point is 20-30 degrees higher, so a few extra quid gets you a longer service interval.

 

There's a comparison of popular fluid standards here

[jp7]

Many thanks for all the replies. 5.1 it's going to be. I'm off to Halfords......

[stevefoster]

Ran dot 4 and then changed to 5.1. On track with big brakes and slicks I notice no fade or sponginess on either normally.

On Dot 4, during an interupted session (red flag) I had to come in on a hot lap without my usual cool down lap. After 10 mins and a restart the pedal was quite spongy and this disappered quickly as the disks rotated and cooled things down.

Not sure if this was pads or fluid.

A long break lets things cool naturally and the pedal isn't spongy then.

 

I haven't needed to do the same 10 min test on DOT5.1.