I am starting a FXS build, which is quite different from what I've built in the past. I have found recommendations on tire sizes, but I would like to know the pros and cons of the differing sizes. The track I'll be racing on is a 1/6 mile dirt oval (Jackson Speedway in Michigan). I have found that 15x8 tires on 8x8 rims for the rear are common. What are the advantages of that size over a 12x9? I am planning on using 11x5.5x6 Hoosiers on 6x6 rims for the front. Also if I were to go with the 15s, could I make a 15in diameter plate to use until I get the tire and rims? Or are the tires not exactly 15? I'm sure it depends on air pressure as well. Thanks in advance.

Your wuestions help me alot. Thanks for asking.