In this episode the Squirrel takes his Mini to the track for a 3rd time and promptly FUBARs his brakes for a 3rd time.
I took the Mini with me to work/ instruct at a autocross/track event at Canaan Motor Club (site of last episode’s brake FUBARing). I made some passes at the autocross layout in the morning (a fast layout with speeds reaching 65mph in my 115HP Mini, with one braking zone from that 65mph top speed to about 35 with a further 4 wheel drift down to about 25 (that corner was beyond slippery when it was wet in the morning) and another from about 55 to 20), after my 3rd pass you could smell a bit of brakes (to be expected when Hawk HP+ pads are driven hard) and the pedal was a tad squishy, something I put down to the fact that I was driving in my sneakers and not my usual racing shoes.
Fast forward to the afternoon and the students are inside learning about track etiquette while the instructors are making laps to dry the last sector of the track a bit (the autocross layout only used the first half of the lap). I’m doing my laps and with every hard braking zone (In my car Canaan has 1 zone coming from 70 to 35, 1 from 55 to 30, one from 75 to 60, another from 70 to 30, and a final breaking point from 45 to 30, all over a lap of about 1:45 so not exactly kind to brakes but nothing quite like the 105 to 30 zone at Thompson) the pedal is getting noticeably squishier. I did 4 laps before calling it as the pedal had reached a point where it was soft enough I was starting to get concerned about it getting softer.
Over the course of those 4 laps at no point did the stopping performance lessen in any way. Despite the soft pedal it was still happy to throw out the anchor every time you hit the pedal. The car still stops exactly the way you expect it to, just with more pedal travel. This leads me to believe the car is just boiling the fluid every time you lean on the brakes.
My setup is as follows: Hawk HP+ pads on Centric cryo-treated rotors (vented in front and solid in rear) installed about 5k mi ago in July, factory steel lines in the body with braided stainless steel lines to the factory calipers (installed with the pads and rotors in July), the entire system was flushed and bled with DOT 4 fluid in July, and then flushed and bled again with DOT 4 Synthetic AMSOIL Racing Fluid in September after I got a soft pedal last time I went to Canaan for an autocross. And now after 4 laps at Canaan it needs to be bled again. It’s really beginning to tick me off that I can’t get my brakes to not die the instant you use them aggressively over about 60 mph. It’s a 115HP car that only weighs 2,500 LBS, why can’t I get it to stop destroying brakes?
After each beating the pads still bite as expected. The pedal just gets soft which leads me to believe the fluid is boiling every time I go to an event. It took 2 20 minute sessions at Thompson on the OEM set-up before the pedal started going soft on me (worth noting that I was actually getting a bit of performance fade on the OEM setup at the end of the first session) and by the end of my 3rd session they were FUBAR. I rebuilt the system with the goal of getting the car to survive a track day but I just made it so that it stops way better but the pedal goes soft in less than 5 minutes. I’m thinking the extra heat produced by the aggressive pads is just too much for the fluid and I don’t know what to do about it.
So tell me Oppo, is there anything I can do to get my brakes to survive track use? Is there a fluid beyond DOT 4 racing fluid that I could put in that won’t boil like this?
I’m really starting to think that I should just put a set of OEM pads back on and give up on the idea of ever tracking this car again. It was rather depressing watching the other cars do lap after lap with no issues when I had to park my car after only 4 laps.