I continue to be mystified by the continuing increase in wheel/tire diameters. For years, most cars had 14" wheels, with some compacts equipped with 13s and large, luxury models shod with 15s. Then we started seeing 15s on even small cars, and now 16 and 17 on Corollas, and 20 on anything regarded as 'sporty', whether SUV or sedan/coupe.
Larger wheels add unsprung weight to the chassis, which causes additional, or accelerated, wear to the suspension components. Same goes for the bigger rubber mounted on those wheels. The only logical reason (other than styling, which the driver can't see from his position) for larger wheels would be to add braking capacity, by increasing the diameter of the rotors, and concurrently adding bigger pads and calipers. This should add safety by improving braking performance (while adding further to unsprung weight, by the way), but I can find nothing in road tests or manufacturers' advertising to indicate what enhancements have been added. Engineering specs, when you get the full breakdown, probably have that kind of data, but it seems everyone just slaps these wheels on and expects the buyer to go along quietly.
Oh, by the way, as many of you already have found out, a 17" tire costs just *a few* bucks more than a 15", and when you get up to 20", be prepared to sink the pablum budget for new skins on the Camaro!
