Brakes

[kenprotheroe]

Any idea why silicon brake fluid is a no - no

for "AP" brakes ?

[m12_nathan]

Both DOT 3-4 and DOT 5 fluids are compatible with most brake system materials except in the case of some silicone rubber external components such as caliper piston boots, which are attacked by silicon fluids and greases.

There is also a problem with mixing Dot3-4 and Dot5 fluids making it very difficult to switch over properly.

A high quality dot4 fluid such as Castrol SRF has a higher boiling point than silicone fluids and can be used without problems, as can a 5.1 fluid such as one of AP's own 5.1 track fluids. No problem in micing 5.1 and 4 either as neither are silicon based.

Castrol SRF is probably the best fluid you can get and I used it in mine along with the vegantune brake cooling mod. It never boiled but is expensive at about £35 a litre.

[DanH]

I thought SRF was silicon based?

I've just had it put in my RS. It does at least mix ok with whatever you had previously.

www.castrol.com/castrol/productdetailmin.do?categoryId=8290039&contentId=6007734

www.castrol.com/castrol/productdetailmin.do?categoryId=82915521&contentId=7001576

[m12_nathan]

It is DOT4 rated so is just like normal brake fluid, along with 5.1. DOT5 is silicon and cannot be mixed?

SRF "exceeds DOT5 temp requirements" but the bottle definately says DOT4. Maybe by messing around with silicon they've changed it chemically so it can be mixed?

http://members.rennlist.com/911pcars/

www.350evo.com/catalog/product_info.php/cPath/22/products_id/55

I'm using AP600 at the moment, seems ok.

[Al D]

Which fluid does the factory use?

[LaurenceFrost]

Read here:
www.stoptech.com/tech_info/wp_brakefluid_1a.shtml

That should tell you what you need to know.

So much wonderful information there.

[v6gto]

Al D said:

Which fluid does the factory use?

Comma 5.1

Martin.