Cooked brakes on track again!

[AceOfHearts]

As a bit of background I have the 283mm brake upgrade on the front of my Chim. Rears are standard and will be getting rebuilt this winter.

After Blyton Park earlier in the year (and cooking my brakes) I replaced the 2 year old DOT 5.1 with fresh, and fitted grooved discs and Ferodo DS2500 to the front of the car. Brakes felt a lot better after this and I was hoping this would fix the problem. The rears are standard at the moment but am planning on getting the calipers rebuilt this winter and refitting with matching grooved discs and DS2500. I don't think the rear brakes are my problem though.

At Snetterton yesterday the car was great around the track and the brakes were not fading, but when I stopped for lunch and came back to the car the pedal was very soft, so much so I had to call it a day and limp the car home early.

I am suspecting this could be the master cylinder on its way out, but has anyone else had this?

[Bluebottle]

Assuming you have already got braided hoses? then get yourself one of these Brake bleeder and some of this Castrol SRF and you'll have fun all day long

The SRF fluid is fantastic and you get no fade or soft pedal whatsoever

[QBee]

Did you look under the bonnet? Was there any leakage from the brake fluid reservoir cap?

[AceOfHearts]

Thanks I will give that fluid a try once the rear calipers are rebuilt and back in. That bleeder looks a lot easier. Doing a bit of reading online it sounds like it could be due to not giving the brakes long enough to cool down before coming in after each session, so the hot discs just sit there and heat up the fluid when back in the pits.

This was only my 4th track day in the car so still a lot to learn

[AceOfHearts]

QBee said:

Did you look under the bonnet? Was there any leakage from the brake fluid reservoir cap?

I did check but no the fluid looked fine

[QBee]

AceOfHearts said:

Thanks I will give that fluid a try once the rear calipers are rebuilt and back in. That bleeder looks a lot easier. Doing a bit of reading online it sounds like it could be due to not giving the brakes long enough to cool down before coming in after each session, so the hot discs just sit there and heat up the fluid when back in the pits.

This was only my 4th track day in the car so still a lot to learn

I have never had this problem, with a similar set up to yours, though I do have braided hoses.
By the way, you do leave the handbrake OFF in the pits between runs, don't you?

[phazed]

QBee said:

I have never had this problem, with a similar set up to yours, though I do have braided hoses.
By the way, you do leave the handbrake OFF in the pits between runs, don't you?

Very much ditto.

Braided hoses, DS2500s, Halfrauds racing brake fluid, dozens of TDs and not a problem, ever!

[ClassiChimi]

Smashing picture
The experts only do say 15 minutes hard driving then say upto two slow down laps to let the brakes cool right off before pitting that will help tremendously,
Then leave at least 20-30 minutes before taking to the track again,,
Hope that helps

[AceOfHearts]

Cheers guys, yes i have braided hoses, but was only doing 1 cool down lap, and yes I was leaving handbrake off when back in

[Richard 858]

Remember to also bleed the master cylinder as well as the calipers when going through a full system check.

[QBee]

Your soft pedal is to do with the hydraulics, not the disks and pads IMHO.