If you are on a 7" rim, I wouldn't put anything more than a 215/40 on. If you are 7.5", then 235/40 will be fine, and the combination you are talking about is what I used to run on my 500bhp Sapphire. I wouldn't fit a 245 unless you had a MINIMUM of an 8" rim. The disparity will be no problem what-so-ever between a 215/40 and a 235/40 tyre on a 2wd car. Obviously if it is 4x4, then the rolling radius HAS to be the same .