Recommendations: Brake & clutch fluid for trackdays

Technical Area Motorsport & Trackday Preparation
2

 Can anyone tell me if it’s worth splashing the cash on upgraded brake and/or clutch fluid for a Mk1 MX5?

After a couple of track days this year I have just replaced all 4 discs with new OEMs, along with Yellowstuff pads, and s/s hoses.

Now it’s time to change the oil & filter, thought I’d put in fresh brake & clutch fluid at the same time.

So is it ok to stick with bog standard Halfords dot 4? Or is it worth paying extra to get:

AP 5.1, or Castrol Response High Performance Synthetic Fluid, or RBF 600…etc etc, as they all vary enormously in price?!

Any advice appreciated Thumbs up

Cheers, Steve.

 

3

 I Run Ap 5.1 Its great and you hear no complates from me

4

Don’t worry about special grades of clutch fluid - the only way to overheat your clutch fluid is to set fire to your car. So cheap stuff will do.

5

 Thank you. I’ll try AP5.1 for brakes and stick with the cheapie stuff for the clutch then. Ta.

6

 As brake fliud is hygroscopic (absorbs water from the atmosphere) it needs to be replaced every 2 years regardless of any other recomendations.

Water trapped in brake-fluid will boil and expand to 15 times its original volume causing vapor-lock inside your brake hydraulics, NOT GOOD any brake fliud will do as long as it han`t been left laying around the garage for years and still has its seal intact.

DR Eunos.

7

 don’t use 5.1 its not really suitable for use in a road car, dot 4 is fine just use a good quality one, millers oils do a good race dot 4 and ate do super blue which is also supposed to be good

8

Tha main thing is not to use DOT5 (silicone).  Not many places sell it, and with good reason, it’s incompatible with  DOT3, DOT4 or (confusingly) DOT5.1.

If the pads have plenty of meat on them, heat conduction to the fluid is quite low so fresh DOT4 should be fine, and is what the car was designed to use.  Very worn pads overheat the fluid more because there is only a thin layer of friction material insulating the piston from the metal backplate, which conducts heat very well indeed.

9

 Thanks for that. Pads & discs are all new so I’ll just flush out the old brake fluid and put in some fresh good quailty Dot 4.

10

 When you get to the point of confidence on track that your brakes are suffering from heat that is the point to change to 5.1