What are the differences between lightweight 17s and 18s?

[Hobbes =^.^=]

One of the major arguments was the extra weight and diameter of 18s affected the car's handling and acceleration.

The wheels that I found weigh: 17"-16.5lbs 18"-19lbs. With that in mind, are the handling and acceleration differences between lightweight 18s and 17s that big?

 

[markmakeitso]

the factors that affect performance for tires and rims, besides traction, are linear inertia, unsprung weight, and angular inertia. unsprung weight and linear inertia are both directly related to the weight of rim and tire combined, but angular inertia (force required to spin the wheels, rather than just move them forward) is related to both total weight and also how far from the center of rotation the weight is located. i don't know of an easy way to compare angular inertia, unless the manufacturers are kind enough to provide it.

the bigger rims, which are heavier, might be offset by the tires, which will probably be lighter than the tires that go on the 17s

 

[Johnny5]

I would assume a smaller diameter wheel would be faster much like the effect of an underdrive pulley. Just a thought.

 

[nutshot]

A tire can cause underdrive if the overall diameter is smaller than stock. If the tire of an 18" wheel has the same diameter as that of a 17" tire, and both tires are of equal width, the 18" tire will be lighter, creating a equality in overall weight (there are variances in wheel tire combo's) between the 18 and 17 combo. Where the most gain is found with an 18" wheel is less sidewall flex while cornering, generating greater friction and sticking to the road better. However, if you drive on bumpy roads (risking cracked rims), drag race (where sidewall flex equals increased forward traction), or need the ride quality benefit of a thicker sidewall (think basket-ball versus bouncy ball), a 17" will definitely suit your needs.