
Originally Posted by
Richard Buckingham
I've been running my SRA for >4 years and I've settled on 205/50-15 at the front and 275/35-15 at the rear running Hoosier R7s. For wheel size at the track you want to max out wheel for whatever tire you run so the tire sits right on the wheel and you get the max contact patch and even wear, so for the 275/35-15 I run a 15x11 wheel, for the 205/50-15 I hear you can go as large as a 15x9 (so the Miata guys tell me!) though I have not tried that large yet.
For larger wheels for your SRA you probably can't do any better than to get the 949 Racing 6UL wheels, we share the same 4x100 bolt pattern as the Miata. For the Atom 3... I have no idea.
TMI are correct that getting heat in bigger tires is harder... but not that hard at the rear on the Atom. Of course it depends how hard you drive the car but heavy braking and acceleration will put plenty of heat in the rears. For the fronts you just have to work them real hard on the brakes too, but on a cold track it just is not going to happen. Some people run A7s to compensate for that. Downforce at the front helps of course if you want to invest in some aero but its not really necessary in order to have a good time and a high performing car. Running lower pressures than you might think is right too. You want to monitor heat as soon as you get off track (probes are not cheap but best, cheaper IR gun can work) and monitor wear. Tune pressures, brake bias, dampers, toe & camber as you see fit for optimal lap times but you should just be able to have a single configuration for everything that at least works ok everywhere and is comfortable and balanced. The factory TMI set-up for the SRA is not bad, although I hear they ship spring rates as 400 front and 300 rear which is weird to me, I run very little toe but add a bit more camber to the back but you can get to those tweaks over time, also depends of course on what tire and dampers you run how you want to adjust those.
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