You can fit any tire on stock sized rims. You could buy forged wheels that are 15x6" (I believe that is stock for you) and make sure they are within 1/4" offset and put 225/45x15" tires on them - if you can find someone who knows how to put a tire that wide on a wheel that skinny.

Personally since it's your 1st season autocrossing I would just worry about driving and less about mods. You could ruin a perfect new set of R tires your 1st time out. R tires do not give any feedback when you are at and past the limit of your car and tires. Street tires squeal before you are about to loose control of your car OR going past the limits of your car.

I would invest in some Falken Azenis, Kumho MXs, or Hankook RS2s. They are faster than most street tires and still give great feedback when you reach the limit of your car.

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