Do i need dot 5.1 fluid

[bassett]

Hi, im in the process of tweaking my kit car in preparation for a track day. Im looking to do either a short taster session or possibly a half day down at Brands. It will be both myself and my dad driving probably at quite a tame level for our first track day in this car. Currently the car runs dot 4 purely as a cheap fluid for its first bleed to get it on the road. The car weights around 430kg, dual master cylinders, bias bar, wilwood 4 pots on vented disc at the front with sierra discs and handbrake calipers at the rear. I understand why you need the better fluids and there boiling points but for real world use what do I need? will my dot 4 do if its fresh or will i require the better quality super dot 4 or even 5.1.
Thanks
Ada,

[GreigM]

the ratings mean very little in reality - Castrol SRF is the best you can stick in your pipes (IMO) - and its only DOT 4

[mmm-five]

DOT 4/5.1 is fine, and no need to bother with silicone (DOT 5) fluid as it expensive, and it's doesn't mix well with water or other types of brake fluids.

Just have a look at the wet/dry boiling temps of the various DOT 4 products and you'll see that while they all meet the minimum spec for DOT4 (otherwise they couldn't put DOT4 spec on the bottle), some exceed it by 50%!

Shouldn't need to spend more than £10 on it, and whatever you've got is probably fine if it's unopened - if it's been opened and left then don't use it as it will have absorbed moisture.

[haircutmike]

Because I was desperate before a T/D I bought and used Halfrauds "Racing" brake fluid, (Dot 4).

Been in for about 10 T/D's in the last year and has had heavy use in the tiv.

Coupled to Hawk HB Plus pads, never a glitch, ever

[TheEnd]

DOT 5.1 is a higher minimum spec, but the top ones usually fall into the DOT4 category.

A good DOT4 is better than the cheapo 5.1

[teabagger]

The brakes on a lightweight car such as yours dont take as much punishment as a heavier car.

Just put in a branded dot 4 and you will be fine.


I have just read what kind of car you are running and it turns out it is the same as mine.
We are still running the standard stuff from MNR (a standard cheapo dot4 probably).
The car has never suffered any brake fade even after a full open pit lane trackday doing double stints (car is shared by two of us).

Edited by teabagger on Wednesday 3rd March 23:47

[bassett]

Cheers guys I wont worry about the 5.1 and just find some good dot 4. Hopefully the castrol super dot 4 will be good as while i was thinking about it i haven't bled the brakes on the Leon which is feeling a bit mushy.

[philmorris]

5.1 material is more hydroscopic than 4; for this reason it is less suitable for long-term applications (like road cars). however, change it after every event, and you'll be fine (if a lot poorer).

As for SRF being "the best", ask the seller (or manufacturer) about its "compressability" rating (which is the measure of performance under pressure); not looking so good now, is it?

[jonamacg83]

Do NOT use Dot5 - this is very different to Dot 5.1. Dot 5 is Silicon based and as such is totally incompatible with Dot 3, 4 and 5.1

If SRF is a bit out of the price range (it is fiercely expensive) I have had good experiences with Motul RBF600 or AP600 fluid. Just starting to use the Carbone Lorraine stuff now, not sure what its like yet though.

[chris7676]

I use Castrol Super Plus DOT 4 (whatever it's called) on a car 3 times heavier, so I can only assume you can use any cheap decent fluid and be fine.

[aww999]

I have more trouble getting the brakes *up* to temperature on my kit! As someone has already said, you are highly unlikely to get the brakes hot enough on a 430kg car to warrant buggering about with a fluid change.