300bhp/ton said:
Not necessarily, on both counts.
Well generally, yes. But I know what you mean.
with 17" Wheels, you will get better traction assuming all factors are the same (ie: using the same type of tires on both the 17s and the 18s). And 18s will look MUCH better, and fill the wheel well gap MUCH better and they will handle better and help making turning more solid. Traction for drag racing or launching MAY be a problem however. I personally have never driven with 18s yet, so I can't say how good or bad traction is over 17s.
Another problem with 18s is that they are very heavy. And any weight added to the car as a "rotating mass" (as wheels are) is very bad. rotating mass-weight is the worst kind of weight for the car. So by adding bigger heavier wheels there will be a loss of power. So with 18s now there is a loss of power AND traction. I have heard some people say on here that they went with 18s and could actually feel that the car got slower. Thats debatable I guess
Personally I will be getting 18s (probably in the winter or next spring of 06) and will be getting the STEEDA Ultra Lights. These wheels are lighter than almost (if not) every 17" wheel on the market, as well as lighter than stock. So if you get 18s, you might want to consider some STEEDAs as they will not make you feel any power loss from adding typical 18s.
ANOTHER problem with 18s is that it will throw your speedo off a bit, so you will need to get it recalibrated. I dont know if a SPEED-CAL can do this for you...can it anyone?
So if it can't, you may need to buy a superchip.
I just got 17" Cobra wheels 17x9 and 17x10.5" (with Nitto DRs) and personally if they weren't from my friend who needed the cash, then I wouldn't have gotten them, because they are heavier than stock, and don't look as nice as the 18s I want will. So I will probably sell them soon...