The difference in sidewall from stock to Alex's 225 is a loss of 36mm in sidewall. The difference between the 225/40's and the 215/40's is only _4mm_. Source http://www.rx7.org/public/tiresize.html > Those Kumho's are 215/40's which you do not want. The overall diameter is > too small and the sidewall will not offer too much protection.