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Vinspin, for 18's, you have to decide if you want a square setup or staggered setup. Square setup means all four wheels are of the same width. Staggered setup means the fronts are narrower than the rear wheels. For 86/BRZs, a good width would be 8.5 to 9.5. With offsets from 45-38. The lower the offset, the farther from the hub or the wheels poke more out of the fender. For an 8.5 wheel, a 225-235 width tire would be good. For a 9.5, a 245-265 tire will do. A narrower(245) tire would stretch more than a wider one(265) when mounted on a 9.5 wheel. Some people want the stretched look and some want the meaty look. It depends on you.
For tires, Achilles 123s are a good set of tires which give really great traction on dry, and give good performance on wet roads. Guys who I track with have tested and proven the 123s. Most of us who track our cars have the 123s installed. A good tire for its price!