Which brake fluid?

[wazza]

I'm having my new disc/pads fitted next Wednesday.
(B5 S4 with grooved OEM discs and EBC redstuff pads).
Which brake fluid should I use? and why?

[Golich]

strictly speaking DOT4 as written on top of the reservior tank. Erwin manual states this as well.

Some of the lads have been talking about using DOT 5 type grades with higher boiling points. I don't very much about brake fluid to be honest so I've stuck with the stuff recommended until I know better.

Worth reading the bleeding brakes posts. Check to see what your service agent is going to do. You might not be 1getting a complete fluid flush that you think your paying for!!

[img]images/graemlins/yellows4.gif[/img]

[JJRS4]

John Roberts recommended Motul dot 5 to me. I guess you need a higher boiling point than standard. Boiling is what puts air in the system.

[Andiroo]

Castrol SRF Dot4 has served me well on trackdays [img]images/graemlins/wink.gif[/img] As JJ says the higher boiling point of the fluid is key. Not really sure on benefits/drawbacks on Dot4 to Dot5 to our applications though [img]images/graemlins/tongue.gif[/img]

Andiroo

[DuncS3]

I have DOT 5.1 in my S3 (I think 5 is the silicone one which is what I dont have) put in by AMD

Dunc [img]images/graemlins/s3addict.gif[/img]

[s2driver]

Have to agree with Andiroo. Castrol SRF DOT4 is brilliant. My brakes are currently peaking over 700 deg C (RS4 disks going blue/cracking and greenstuffs melting!) and the fluid is still good.

Am addressing the disk and pad issue by getting a few F1 spec floating disk setups made next week by an F1 supplier. Only difference will be a heavy iron disk (instead of carbon).

[img]images/graemlins/rocker.gif[/img] [img]images/graemlins/rocker.gif[/img]

[DuncS3]

interesting about the temperatures, my brakes (using a electronic thermometer) read 152 degress straight after coming off the track. Is that the same sort of reading you are talking about?

Dunc

[DuncS3]

reading a thread on scoobynet about a brake group buy, someone said this:

"They do an "Extreme 5" Brake Fluid which has all the properties of a 5.1 apart from the fact that it will not eat through your seals on the master cylinder"

is that a fact or just Subaru related?

Dunc [img]images/graemlins/s3addict.gif[/img]

[foomans2]

HI,

Castrol SFR for me too. It's not cheap, but it has an excellent wet & Dry boiling point.

Anyone able to arrange a group buy?

Cheers
Steve [img]images/graemlins/24430-audibash.gif[/img]

[johneroberts]

Motul dot 5 [img]images/graemlins/grin.gif[/img]
why accept anything les than the best [img]images/graemlins/acclaim.gif[/img]
jr

[JJRS4]

Anyone who comes straight off the track with very high temperature brakes has obviously not done a cooling down lap - the most important thing to do on track days and, of course the only time anyone will overtake you. Give them the thrill of it!

[Andiroo]

Equally as important as a warm up lap JJ, IMHO - a far to often overlooked trackday rule [img]images/graemlins/wink.gif[/img]

[s2driver]

I am peaking 700 degrees on the disk surface on the road!!! Will be getting heavier disks to reduce their temperature (increase durability) and changing the pads to run at higher temperatures. There is no problem running the brakes hot if all of the materials in place are designed for those temperature levels. Besides, radiative cooling is far greater from hot bodies (proportional to temp^4 as are convective losses) so you will loose far more heat energy from a hot system than a cool one in a given period of time, all other things being equal. One of the main reasons why high end motorsport try to run their brakes at the highest temperatures possible so they can dissipate the energies involved much quicker and hence design fade out of the system too with relative ease.

Lee

PS I hear good things about AP600 (and the lower temp AP551) fluid too but have no direct experience.

[simonelman]

F or C ??

[JJRS4]

Warm up lap Androo? [img]images/graemlins/wink.gif[/img] Once the red mist descends and the target to catch is the 5 sec man in front, thoughts of warm up go right out the window. But very good advice - cold tyres, cold brakes, cold engine - cold shiver.