Dot 4 Dot 5 etc etc

[E36GUY]

Can someone explain all the differences between Brakefluid DOTs etc.

I have some AP racing fluid 600 on order which needed to be here today as my car is booked in to get its brake hoses swapped for braided ones and the brake fluid changed. I've already changed all the pads at the weekend for more racey versions. Seems however that the fluid is unlikely to arrive today which scuppers the booking I have at the garage and there are no other days available until next week. Going to the Nurburgring at the weekend so really wanted this all done. Can anyone recommend a fluid type that my local garage can pop in tomorrow that will do the job? Bear in mind I'm no race driver but the brakes will get hot.

[Munter]

What you want is some dot 5.1.

Start ringing local motor factors and asking for dot 5.1 brake fluid is my suggestion.

http://www.stoptech.com/tech_info/wp_brakefluid_1a...

edit:because I wasn't sure I'd got the compatability of fluids right. But 5.1 is the stuff.

Edited by Munter on Monday 17th March 15:23

[E36GUY]

Getting the fluid changed completely so no worries on mixing one with t'other.

Why DOT 5.1. I'm buggered if I know the differences. I guess it's all about temperatures etc.

[chrisr29]

Dot 5 has a higher boiling point, don't know what it is specifically though.

If your fitting new pads try and bed them in before you go. Pad fade is just as bad as boiling fluid when you are trying to stop in a hurry. I find the best way is to take it easy for a 100 miles or so and then hammer them to the point of pad fade (The peddle will feel hard but the car wont want to stop) let them cool then you should be fine.

[Munter]

E36GUY said:

Getting the fluid changed completely so no worries on mixing one with t'other.

Why DOT 5.1. I'm buggered if I know the differences. I guess it's all about temperatures etc.

Yeah basically. The higher the DOT number the higher temperature it can take. They are all compatible except 1. Which is DOT 5. Thats based on different chemicals and might affect seals etc. But (having read the link below) dot 3 dot 4 and dot 5.1 all work happily in the same system.
http://www.306gti6.com/forum/showthread.php?id=283...

[E36GUY]

okey doke.

Thanks guys

Chris - yes. Done 100 easy miles on them already and have the 300 mile drive all the way to the ring on Friday to bed them in more.

[richardb.jones]

Munter said:

E36GUY said:

Getting the fluid changed completely so no worries on mixing one with t'other.

Why DOT 5.1. I'm buggered if I know the differences. I guess it's all about temperatures etc.

Yeah basically. The higher the DOT number the higher temperature it can take. They are all compatible except 1. Which is DOT 5. Thats based on different chemicals and might affect seals etc. But (having read the link below) dot 3 dot 4 and dot 5.1 all work happily in the same system.
http://www.306gti6.com/forum/showthread.php?id=283...

not strictly true - I believe most (if not all) the high performance / racing fluids are DOT 4 - not 5.1 - I think this is because they do not meet performance figures for a 5.1 at certain temperatures. ie when -40 Deg C but that means they cannot call it a '5.1' fluid - but in all other aspects (wet/dry boiling points) the DOT4 racing fluid is vastly superior to normal DOT 5.1

[E36GUY]

oh FFS.

Does this mean I should be using DOT4 then?

[Munter]

Umm possibly you know. I just checked my stuff and it's DOT 4. But has a Dry Boil of greater than 300°C and a wet boil of 195°C.

Compared to the 5.1 standard of
DOT 5.1 Dry: 260°C Wet: 180°C

I think the answer is you need to speak to the motor factors and ask them what high temp brake fluids they have. Look them up and the net. Then buy the one with the highest boiling points.

[boxsey]

You cannot mix Dot 5 with the others (Dot 4 and Dot 5.1) unless you have completely emptied the entire system because Dot 5 is a silcon based fluid whereas the others are glycol based.

You CAN put Dot 5.1 (e.g. Castrol SRF) in a system that previously had Dot 4 as long as you completely flush the system. Castrol SRF is pretty expensive especially when flushing the first time. The alternative is to get 'super dot 4' e.g. ATE blue or Castrol Response and put that in.

HTH

Here's a useful link for you:

http://soarer.ace.net.au/brake_fluid.html

[Monty_M100]

I`m no expert, but these seem to be the best

Castrol SRF Brake Fluid but expensive.
http://www.raceparts-direct.com/products/fluids_an...

Motul RBF600 High Performance Brake Fluid comes in 500ml
http://www.mocomracing.com/product_details.asp?id=...

ATE Super Blue Racing Brake Fluid
http://www.k300performance.co.uk/ate-super-blue-ra...

but you`ll find it difficult to get these from your local motorfactors, if you can`t get these then 5.1 might have to do but i`ve boiled this on track so take it easy on your brakes

[Birdthom]

DoT 4 or DoT 5.1 doesn't matter as much as the quality and boiling points. For instance, Halfrauds sell a "Racing" (their words, not mine, it has a silver label rather than an orange one) DoT 4 which has higher boiling points across the board than their DoT 5.1. I've used both and they've been fine, so I haven't needed to spend any more on RBF600 etc. My car is only about 1000kgs/165bhp though.

I have used boggo DoT 4 and even DoT 3 before if there really is nothing else to hand, but I wouldn't use them again as they boiled up pretty quickly.

HTH.

Edited by Birdthom on Monday 17th March 20:13

[pikeyboy]

I use the ap racing stuff in the race car as its only a few degrees off of the dry boiling point of castrol SRF but is about a 1/4 of the cost. I used to use ATE super racing blue, eurocar parts sell it for about 12 quid for a litre.