I am a budget autocrosser who wants to retain my BBS 17 x 7.5 wheels. My Bridgestone RE070s are now ready to be replaced. I run in the STU class and would definitely love to run the class max width of 245, but I don't want to buy new race wheels. The tires that I plan on running will be the Bridgestone RE01R. Could some tire expert (Luke) explain to me the difference of the 235/45/17 and the 235/40/17 and why the 40 series tire can be put on a 7.5" wheel and the 45 series tire is recomended to be put on an 8" wheel. Originally I was just going to go with the standard 225/45/17 but would like to go a little wider on my stock wheel. Thanks in advance for any reccomendations.

 

The second number is the profile percentage. Soo... the first number is the width. 235mm. The second number represents the percentage of the first number. So... 40% of 235, or 45% of 235mm. Essentially, the two numbers determine the diameter of the tires.

 

2005/2006 national STU champion ran 245/40/17 yokohama neova ad07s on his stock 17x7.5 bbs wheels fwiw so it can be done. Take a look at the new dunlop direzza z1 tire too. It's been getting great reviews for our heavier cars.

 

the top three choices would be

Potanza RE01R
ADVAN Neova AD07
Direzza Sport Z1

 

do you know if you could fit a 245 re-01r on a 7.5 wheel?

 

the 225/45-17 would perform as well if not better on the 7.5" wheel ... with the sidewall pinhed in on the 245 the contact patch would be almost the same but, you would have more sidewall deflection and less contact patch control