smaller vs larger wheels - Whats the diff?

[Spokane540ia]

I'm interest in what having smaller vs larger wheels do?

I know if you like 20's you like the way they look. That's not what I'm asking about.

What are the performance differences, what performs better? Why?

What are the trade offs?

My Sirocco 16V, back in the 80's I believe had 14's instead of 13's. My Subaru Outback has
15's as opposed my old Legacy Wagon which had 14's (instead of 13's)

My 540 has 17's (as opposed to the 16's it came with) My friend 2006 M4 coupe has 18's.

Can anyone help me? Is it just fashion?

I know there are issues with sidewall width, unsprung weight, and so on.

But I have not found a definitive answer!

Please help if you know, (and please don't answer if you don't)

also posted this in the E39 forum, thinking this may apply to more people:)

Marv

[frasc]

I am not a super car guy, but as far as I know it depends on the size of the wheel gap and what you can fit on your car really. The wheel size + the tire size should be constant on your car so if you get for example 16" wheels and your tires are 3" bigger then that is 19". If you upgraded to 17" wheels you can only get tires that are only 2" in order to keep the total at 19.

Because of this, if you upgrade the wheel size, you have a more rigid wheel closer to the pavement and less tire to cushion the road. So you will have a slightly bumpier ride by having bigger wheels and smaller tires. I don't know if it provides any benefit beyond looks though. Someone else on here can correct me if I am horribly wrong.

[terranuser]

Usually bigger wheel means more weight, so your unsprung weight goes up. This will adversely affect car's straight line performance. Since your wheels are heavier, it takes more energy to rotate them, compared to lighter wheels.
However, bigger wheels will give you better cornering performance (as long as the wheel is not ridiculously big) since you will have (generally) shorter, meaning stiffer, sidewall, which translates to more and stable traction to the ground. And since your sidewall is shorter, the ride will be more rough, compared to bigger sidewall wheels.

[cam99]

Usually bigger wheel means more weight, so your unsprung weight goes up. This will adversely affect car's straight line performance. Since your wheels are heavier, it takes more energy to rotate them, compared to lighter wheels.
However, bigger wheels will give you better cornering performance (as long as the wheel is not ridiculously big) since you will have (generally) shorter, meaning stiffer, sidewall, which translates to more and stable traction to the ground. And since your sidewall is shorter, the ride will be more rough, compared to bigger sidewall wheels.

+1 , bigger wheels = better looks but at a price.

for example, my vette, lowered with 19in in front and 20in rear

http://corvetteforum.net/c5/cam99/

looks cool but .....