RE: 17" wheel questions
I'm talking in very general terms here. I know when I went from stock size to 245/50/16 the car handled much better, less sidewall deflection is part of it. Then when I upgraded to 17 inch rims with 245/45 and 275/40 the handling went through the roof, I couldn't believe it. It wasn't just because of having better tires either. The 245 16 inch tires I had were high performance eagle gs-c tires, very grippy. There are a lot of variables that factor into handling and responce. I think one major factor is tire type, sidewall size, and width. The better you match the tread width the rim the less the tire can deflect on hard cornering.
here's some good reading
http://www.valvoline.com/carcare/articleviewer.asp?pg=pht20020101mu&cccid=4&scccid=2
quote:
"With all those changes, don't forget the wheel and tire combination. First determine which general category of tire suits your needs. Daily-driver vehicles should have tires that provide longer treadwear and possibly a smoother ride. Street cars that see occasional track time would be better fitted with a lower-profile, better-handling tire, possibly with upsized wheels. For all-out performance, racing tires are essential, but keep in mind that they may not be the best or legal choice for a street-driven vehicle. If you live in a very wet or snowy area, you will definitely want to take weather conditions into consideration.
Increasing the size of the wheel while decreasing the height of the tire is a simple and effective way of improving handling performance. A low-profile tire decreases sidewall deflection and enables a faster turn-in and improved cornering stability. This increase in handling responsiveness may be less noticeable if your car retains the factory suspension components. Also, you'll probably notice a tradeoff in ride comfort for performance. Low-profile tires give better handling but at the cost of increased road noise and vibration transferred to the suspension.
When changing wheel and tire sizes, keep in mind that in order to keep your speedometer and odometer fairly accurate, you'll have to stay within three percent or roughly 3/4 inches of the original overall diameter of the wheel and tire combination. Any increase in size above this range will require recalibrating your speedometer. For instance, a 15-inch wheel with a 60 series tire could be upgraded to a 17-inch wheel matched to a 40 series tire. "