I have an 03 Cobra convertible and want to change my wheels to a custom 18" wheel. I have looked everywhere on the Internet and it seems wheels for the 03 Cobra are either expensive or cheap. I did however find a wheel that I find attractive, the Dale Ernhardt Killer but the wheel for the front of the car is an 18 x 8.5" wheel and the stock Cobra rims are 9". The Tirerack rep says the .5" differenceis inconsequentialbut my performance adviser says I should run nothing but a 9" or even better a 9.5" wheel. I need help from anyone with knowledge or experience in this area.

 

Don't look for 03 Cobra rims then. Look for 5 lug... what, 94-04? I dont know about the 05+ wheels. If you go back to Fox they were 4 lug. Either way, all the 5 lug wheels work from 94-04 at least.

The 8.5", 9", 9.5" numbers are your widths. With an 8.5" width you're talking a pretty skinny tire for a Cobra. I'm by no means an expert on it but I think that may be around a 245-265. I agree with your performance advisor if you want any chance of ever sticking to the road.