[hdrewh]

Basic question: all else being equal (suspension, tires, staggered setup or not, etc.) what is the performance benefit, if any, of 18" over 17" wheels?

Thanks,
Howard

[preDoc 328]

I'm no expert, but I have been researching wheels for a while. I don't think the size of the wheel matters as much as the width and weight of the wheels/tires you run. Wider wheels should give you more contact patch, leading to increased grip levels. Going up one inch in wheel size is probably more cosmetic than anything.

For example 17x9 wheel should grip better than a 18x8 wheel, whereas an 18x9 will be better than a 17x8. As for 17x9 vs 18x9, I doubt there will be any difference. It is the cost of tires, as well as how wide they are I believe. Any real experts plz feel free to correct me.

[HighlandPete]

Depends what you mean by 'performance', and is it for day to day driving, or track use.

Width isn't everything either, tire 'width' selection, for a particular rim size, can make a difference to 'balanced' performance, over a range of conditions. Even traction grip and lateral grip are not simply a rim size, or width issue. A better tire, running optimum pressures can be a better performance enhancement than 'up sizing' rims.

One problem with increasing rim size and width is, when driving poor road surfaces, we lose some road contact and this can translate to a decrease in performance. Skitter, poor road follow, can be the trade off, for increasing rim sizing.

A good example, the E46 M3 drives better on 18" wheels than on 19" wheels. track lap times have been proven to be faster on the 18" wheel setup.

HighlandPete

[JoosyJoos]

The main performance difference between the two rim sizes is really the weight. Less sprung weight is always going to perform better. Some of the other factors have already been spoken for...

[hdrewh]

Thanks guys. My question is primarily because a. I don't know the answer and b. eventually I'd like to upgrade my non-ZSP suspension and would be wondering if I should get bigger wheels also. My driving is basic daily driving, possibly twice/week to where I work in NYC where roads obviously suck. I wouldn't be tracking the car. So I lean towards keeping the 17's eventually with non-RFTs, but if 18's provided a clear advantage I'd consider them. From the replies so far....they don't.

Looking forward to hearing more...

Thanks again,
HH

[JoosyJoos]

You wouldn't see any benefit unless you like heavier rims, more expensive tires, and a harsher ride lol. Only downside is that 17" rims look tiny.

[preDoc 328]

How much harsher is 17in to 18in? Was is very notable? I am thinking about going from 16-18in pretty soon...lol

[reprod]

Originally Posted by preDoc 328

How much harsher is 17in to 18in? Was is very notable? I am thinking about going from 16-18in pretty soon...lol

Are sticking with RFTs? If you are sticking with RFTs you will not feel much of a difference. If you going into non-RFTs then there is a noticeable comfort difference between the 17s and 18s.

I have KWv1 and 18" OEM 189 wheels and I drive in NYC every week. If you know the roads you take you are golden... If you like to drive in a straight line and eat potholes then the chances of a bent rim are much higher with the 18s.