I think tires are the #1 tuning option on a 12th-so I used to have in all different sizes:
Front:
TRC Purple, Tan and Magenta
Jaco Purple, Dbl PInk.
Rear
TRC Grey, PInk
Jaco White, PInk.
And all these compounds are for Carpet. YEs-Caster-T-bar thinckness, Old school vs. Re-active caster front end, side srpings-damper lube all work towards the balance of the chassis and are very important-but tires can make the biggest impact in lap times and Driveability.
Ray