Then below that you will see the carnage that occurred during my last session of the day. Brakes failed and I went off and narrowly missed a barrier. Had to ebrake back to the pits where I discovered mushroomed and grinded brake pistons, warped backing plates, destroyed Polymatrix pads, bent pad pins, and my passenger caliper ON FIRE. Needless to say I had to get the car trailered back by a friend. I'm working with Wilwood to get the braking kit replaced. Hoping they step up.
Someone linked me to this for some input.
First a very unfortunate situation that could have been worse. Dodged a bullet a bit on this one...
That being said...Polymatrix E compound pads are NOT a race compound for open track use. (nor are the stock BP10 pads that come with the kits). E compound is an elevated street compound which would be ideal for Autocross use and parking lot Solo events. It's roots are in dirt track and lighter weight vehicles.
What happened was the sustained high temps allowed the compound to break down and the binding agents to come apart. Much the same as the original BP pads. The E pads have perhaps an elevated temp range of up to 7-700f and while they could be pushed maybe beyond that in a rare event only ample cooling time would allow for enough recovery to do it again.
The entire Factory Kit is an exceptional value but it is not a racing kit. The limitations being: light weight, non directional rotors, pads of only 12mm thickness and compounds not suited for extended open track use. There's nothing wrong with the kit...and to that end this was no so much 'brake failure' as it was the wrong equipment for the job.
To maximize the Fiesta kit you'll need: Heavy duty GT rotor castings, race pads such as H compound, some Titainium heat shields and some ducting for cooling. At that it will remain "rotor challenged" in the size of only 12.2 x .810". Most race sets are a minimum of 1.10" and more ideally 1.25" castings and today put 14" or more. The Fiesta doesn't need quite all that...but the Fiesta kit was not engineered for a track day use- coming well before there was an ST model in fact.
Please get some of the more suited parts for this use and build in some greater margin of safety.