Been playing with race cars of one kind or another my entire adult life and tires and tire rules have always been a hotly argued topic. No tire rule or the lack of any tire rule, someone is going to be unhappy.

In my experience, treadwear limits seem to be the best compromise. 140, 200, 500, whatever, it really doesn't matter. 200TW is the number most bodies settled on so 200 it is. That's how the TW rating for CAM was decided. Most other series that promote pro-touring autocrosses require 200TW so it would be the same in SCCA's rules. From what I understand 140TW tires are on their way to becoming extinct so 200TW will be the softest UHP tires in regular production by most manufactuers in the near future.