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A quick aside on tires

Over the last few months, I went through a few different types of track tires on the M240. Figured, I'd share my notes here.

No, I didn't test them back to back on the same day, but we'll use Sonoma in the morning (ambient temps 60-70 F) as a bit of benchmark. Car setup stayed the same with all these, which I think makes for an interesting comparison. Even if the tires are in pretty different categories from each other. All tires are 275/35/18. Typical disclaimer, tires are very setup dependent -- don't trust a random guy on the Internet, do your own testing.

Bridgestone RE-71r (33-34 psi hot, 1:55.X at Sonoma)
That's the benchmark I'd been used to over the years. Pretty good for a street tire. Takes no time to warmup, but also gets greasy pretty fast. Ok in the wet. Discontinued now, it seems.

Nankang AR-1 (30-31 psi hot, 1:53.X at Sonoma)
Nice big step up in grip from the 71r. Surprisingly lasts about the same as them. Setup-wise, didn't seem to like as much camber as the other tires here. Sliding it is manageable, but a little chompy, not quite smooth. 275/35/18 seems impossible to find in the US now.

Pirelli PZero DHH (28-30 psi hot, 1:52.X at Sonoma)
I'm really not doing these slicks justice, since I got a takeoff set from a racing team (with presumably 1-2 race heatcycles on them) and put another 4 HC before taking them to Sonoma. Wasn't as life-changing compared to the Nankangs, as I'd expected. I'm sure stickers would blow the socks off any other tire I tested (everyone I've talked to says their first HC is crack). Very good and progressive (though quiet) when sliding. They lost longitudinal grip way before lateral -- as long as I was careful with the throttle / brakes, I could eek ~10 HC on top of whatever they'd done before.

Toyo RR (29-30 psi hot, 1:51.X at Sonoma)
Pretty popular race tire with NASA. I've run them on many other cars, but felt a bit different on the heavy M240. They definitely like their slip angle (nice and smooth), and get pretty loud when you get them near the limit. Could use more camber, especially compared to the Nankangs. Grip peak was high, but relatively narrow compared to the others here -- had to constantly dance on the wheel throwing the car between US to OS to keep them there. Lasted about 15 HC (though slowed down a bit after ~10).

Hankook Z214 (C51 compound) (~29 psi hot, 1:50.X at Sonoma)
Fun tire. First heatcycle felt bananas (but times don't reflect that, someone put it in the wall early on during that outing). Wider grip peak than the Toyos, also quieter. Fronts started going after only 6 HC, which is not great. Needed pretty extensive warmup. I haven't driven Hoosier R7s, but it seems like they're pretty similar.