Question about matching tires to wheels

[5lbsofswisscheese]

I've been looking around at various wheels and tires on the net, and realised that a few places (like tirerack.com and wheelmax.com) seem to be recommending 225/40R18s with 18"x7" wheels. However, just about every tire company has in the specs that the 225/40R18s are approved for 7.5" to 9" wide wheels. Is it safe (much less wise) to put that size tire on an 18"x7" rim?

[goodvibe]

I wouldn't do it. You can probably get away with it but expect a possible abnormal wear pattern. The sidewalls will be softer and you'll want to run higher pressures for stability and to protect the wheel. That will adversely effect the contact patch on a too small rim. It comes down to why you're doing it. Looks or handling. Handling wise you should go with a wider wheel of probably 17" diameter being the best bet. Lighter and enough sidewall for realworld tracking. In any case for handling the wheel should be towards the wider side of the tires recommendations. Wider rim gives a firmer sidewall. Narrower gives a softer one.

[5lbsofswisscheese]

I was actually thinking about it for looks and handling. I would go with 18x8s, but I would like to start doing autocross again in the STS class, which only allows up to 7 1/2" wide wheels.