135i at Homestead - Observations

[MidlifeRacing]

Took the new 135i out to Homestead the other day.
It's been 2 years since I last tracked a car out there, but I've run the course many times. Was very rusty during the first session (combined Solo/SuperSolo run group)- my timing was very off, but by the second session, my brake and turn in points were coming back to me.

Car setup:
KW v1, -2.0 F / -1.5 R Camber
Vorshlag Camber plates
34 psi all around on the stock run flats
Ferodo 2500 front and rear (used thin ti shims up front)
Motul 600

Observations:
Powertrain
Compared to previous cars I've tracked (WRX, RX8, Miata), I found myself shortshifting this car on the straights- there's power everywhere, no need to wind this car up high in the rev range, especially on a casual track day.

Suspension
Even with the modest suspension/alignment upgrades (which have drastically encouraged a crisper turn-in response), there is still a slight tendency to understeer. I didn't fiddle with tire pressure so as to establish a seat of pants base line for the day.

Brakes
Given my driver rust, I didn't brake as efficiently as I normally would have (also this is a new car to me, so I had to adjust to this car's braking as well, so my landmarks from years ago weren't working exactly, as I was carrying much more speed in to brake zones due to the straightline power of this car). I found myself braking either too early or too late at first and triggering ABS frequently. The result was a 20 minute first session ending in severe fade on the last lap where the pedal went completely mush and the car broke squirrely in a long brake zone- came in right away. During the second session, I modulated brakes a bit better got the trail braking working smoothly and drove more of a momentum line with earlier turn-in points. Stayed out 20 minutes, but came in before experiencing any severe fade (though I felt some loss of braking performance towards the end of the run). Later runs, I pussyfooted around a bit, driving more conservatively since I knew the fluid had reached its limits on earlier sessions and was not up to par. Biggest shame is that I had 60 minute run sessions and could only stay out for 20 minutes max before reaching the brake's limits.

Tires
At 280 UTQG I wasn't expecting much, but I was surprised to see the limiting factor in this car was the brakes rather than the tires. The tires, for what they are, held up rather well and provided an acceptable amount of grip to succussfully negotiate the track and point the car to where I wanted. They gave up a bit in low speed turns but would give me decent feedback as to where their limit (in understeer in this case) was. Compared to your 200 UTQG track day tires, there were a bit more slippery, but the compound did not chunk and they even held up to the NASCAR turns 3 & 4 on the Homestead Grand Am circuit which we used which eats up the inner shoulder of tires (contrary to the outer shoulders being taxed on your average course).


As for the track day itself, I showed up on a Sunday and was the only solo driver not to have driven on Saturday. As we staged I realized I should not have gotten in line up front and of course, the frenzy of 2nd day drivers with Saturday's runs fresh in their memories, crowding my rear view mirror and the thought of running the NASCAR turns 3 & 4 (a first for me and not usual for an HPDE) had me a bit concerned given my past 2 years of exclusively driving a mini van. After trying to keep up at first, I soon realized the extent of my rust and pointed by as many people as I could to keep the rear view mirror clear so that I could concentrate on learning the car and relearning the course. By day's end I was really enjoying the freedom of the full course passing zones and was keeping up with people whom I eagerly pointed by on that first session. Without safety equipment installed, I kept speeds under 120mph.
Compared to my old RX8 (which did not tend to understeer), this car is not as well balanced, less eager to rotate and the steering/pointability is less finessed. While the RX8 was more rewarding through the turns, this E82 has the potential to be more fun overall with some better heat resistance in the brakes and a bit less understeer.


On the agenda for next outing:
2pc rotors up front

[ECSTuning]

The run flats holding up is a rather big surprise to me, I've had numerous guys complaining of destroying stock run flats in HPDEs. It sounds like you had a blast. When you're ready to jump into the two piece rotors shoot me a PM and I'll get you set up.

[syenisch]

I can attest to the RFT's as not that bad for HPDE. Not the best obviously, but you could do far worse. I did 2 DE's on them and they held up very well. Honestly I think they are much better than what they are made out to be on this forum.

[neilvosko]

Glad you had fun and knocked the rust off. Hms is a fun track, which group did you run with?
I run the 335i and an LSD and square tires will help you rotate around the turns like a ballerina. M3 bits on the suspension will help as well.