HI,just about to order 18" wheels ,but does it take the performance away??
please help?

 

Yes. Generally 18's are heavier than 16's or 17's (depending on the wheel of course), plus more of the weight is pushed further out towards the edge of the rim, which is even worse for performance (more rotational mass).

If you are concerned with performance, stick with a 16 or 17 inch wheel. 17 is a good compromise between looks and performance.

 

depends.....i'm sure there are some forged 18's that are lighter than the OEM....or maybe not?

 

Larger wheels also make your final drive ratio taller, which decreases acceleration a bit.

 

Saab9-3 is partly wrong - it is the tire outside diameter that determines a change in final drive ratio, and the worst you can do is like 3%. As for lightweight 18" wheels, stock 16's still have the acceleration/braking advantage.

 

Incorrect. Tire size plays the ultimate role in deciding if your final drive will be affected.

 

Hi,so the best way is to buy the lowest profile tyres so the rollong radius will be smaller it the tyres have thiner walls??

IM I RIGHT OR WRONG

 

Well you also want to make sure you tires have large enough sidewalls to protect the rims from damage from pot holes. So I would try to keep it close to stock.

 

You can have 18" wheels as long as you choose the right aspect ratio for the tire. You will maintain overall rolling diameter of the combo and not affect the gearing of the car.

 

If you go with 18's no matter what.....you will effect gearing..

a 255/35/18 stands taller than a 225/50/16

If you follow plus sizing for example:

an S with OEM 205/55/16 front and 225/50/16 rear will be lower to the ground than an S with 225/40/18 front and 255/35/18 rears.

18's without a drop look like crap IMO.