Lost brakes at track day

General
1

So i got some second hand 6 pot Mountune brakes, they look great and appear to be in excellent condition.

All has been well in normal use but when i was at the track day the pedal completely went to the floor after several aggressive laps. Had done about 20 laps before this, over 2 goes, with no issue.

I was luckily enough near the pitlane so off track quickly but needed to use the handbrake to make the car stop. After leaving the car for 15 minutes, the brakes were usable but felt a bit spongey.

I have barely used the car since as they don’t feel as good as i think they should be. I had done a few previous track days with the standard brakes, and never had this issue.

Anyone have any ideas?

2

What pads are you using?

It sounds like the pads might have gotten too hot and glazed during the process, or you could’ve cooked the brake fluid.

3

They’re using the Mountune performance brake pads.

From what I’ve found, it does seem like it could be the fluid. If that’s the case, one solution would be to replace the brake fluid with a high-performance, heat-resistant fluid like DOT 4 or DOT 5.1, which can handle higher temperatures without boiling. Also, flushing the system to ensure there’s no old fluid left in the lines could help prevent further issues.

4

You should definitely change your brake fluid, switch to high-performance brake lines, and consider running DIY brake ducting. The upgraded fluid will handle higher temperatures, the brake lines will improve durability, and the ducting will help keep things cool during heavy braking.

5

Braided lines should be solid, so that’s good. Upgrading to a more performance-oriented brake fluid sounds like the right move, as it seems to be the weak link right now. Look for something with a higher boiling point, like a DOT 5.1 or a racing-specific fluid, to keep things in check during those intense braking moments.

6

I highly suggest considering the DIY brake duct mod if you’re gonna track it a lot

Depending on your generation of ST the torque management system will heat the brakes pretty bad

7

The general consensus is that a spongey pedal usually indicates boiled fluid, while a stiff pedal that won’t stop points to overheated pads.

Adding cooling and higher boiling-point fluid should help, and you can go from there.

Also, you can always refit the fog lights after a track day; adding a removable duct won’t be too much work.

8

What spec brake fluid are you using?

Also, cooling through the front fog lights really does make a huge difference.

9

Honestly, I’m not sure either since my mechanic installed them, but I highly doubt the fluid has been upgraded from the standard one.

I wouldn’t mind looking into cooling through a different method than the fog lights, as I never use them. However, since it’s my daily driver and needs to pass the annual car tests, I can’t remove the fog lights — it would fail without them.