Originally Posted by mastek
... I will be using this BBK once a month @ the track for HPDE events...
This will consist of 4-5 25min. sessions per event ... and each session will include a warm-up lap, 4-5 hot laps, and a properly slow, cool-down lap ...
My worry is 'overheating' -- since that was/IS a major issue with the OE brake system ...
And what is the pad shape number for reference?
It will be interesting to see what Chris says, but I thought I'd describe my experience of M3 braking.
First, my track days are different than yours, in that the track opens at 9:00AM for three hours until lunch, then at 1:00PM for three hours until closing. It's open lapping with 24 cars and no run groups - we're all "advanced". My typical day is 200 to 250 miles, depending on which track we're on.
Success for a day like that is all about pacing yourself and the car. If you cook your brakes at 9:15 in the morning, you lose the day. It's a bit like running an enduro - you have to plan ahead and pay attention to the signals the car is sending about how it's doing.
On days like that, my stock brakes with Pagid RS19's, stainless lines and Castrol SRF were "all over the place". Constant vigilance was needed. Brake fifty feet later at the hairpin than last time, you're rewarded with a spongy pedal for the next two laps.
I upgraded my brakes to the AP/Stillen kit in two stages, and I ran one track day with the front-only configuration. It rained in the morning and was dry and hot after lunch.
After I installed the front-only setup the factory rear brakes that I hadn't upgraded were still prone to overheating, and they became the limiting factor in brake management. I've read what Stoptech says, but on my M3, my experience was that the stock rear calipers were still on the brink of fluid breakdown.
The four-wheel setup fixed everything. Balance is perfect and braking is perfect, and I've continued using the Mintex pads that the kits came with. I have a set of Pagid RS29's for them, but I've never been inclined to even try them; the Mintex pads are excellent. Between the AP brakes with Mintex pads and Castrol SRF, my track day prep amounts to changing the tires. I flush the fluid once in the spring and there's no need to bleed during the season. This convenience factor was something I specifically wanted and I got it with the AP/Stillen kit.
Now, I'll admit that maybe it works for me because I'm just naturally easy on brakes. I don't know, but I can say that I'm still on the stock suspension, I haven't taken the front backing plates off and yet I'm running within a second or two a lap of heavily modded E46 M3's.