2.7tDallas

any what type of engineer are you?

Just Me

All my professional experience is in EE
MIT

Why. Does it change the facts?

If i was say, a chemist or an economist ( which i also am) would the relationship between mass ad acceleration change?

I really am sorry to annoy you, since you contribute a lot o thsi forum, but I think facts matter.

Grant

joeq10

will stick with 17's. I may still change the wheels just for a new look (love the wheels on 2.7tDallas's machine!)

Just Me

Proving that I can talk out fo both sides of my mouth.... If you do go 18s, which can look very nice, my advice is to get light, strong wheels. This almost invariably means high pressure forged. Light to minimize the effects i discussed. Strong to keep them from bending.

Enjoy either way. Maybe the biggest input factor is the quality of your local roads.

Grant

joeq10

A question from the novice wheel guy. Do "strong wheels equate to more expensive wheels (I'm trying to keep the cost around $150/wheel or less)? I love the aggressive look of the wider stance of the bigger wheels, but I definately do not want to sacrifice performance.
I know wheels are a subjective call, but any suggestions you might have (given my cost limitations) would be appreciated. thks. joe

4Driver4

That is the right advice no matter what size is selected. Pat attention! Wheel weights can be stupidly high.

Just Me

Unfortunately, yes, and in a big way. For example, a 17 x 8 cast wheel from a good manufacturer like BBS might be $200- $225. Their forged gold line might be $400+. I cant say exactly because once you're in that neighborhood, i change my mind :-) One manufacturer that is said to have good, cheap ( relative term here) forged wheels is ENKEI.

I'm very much atypical in that I'm fine with smaller wheels. I have 16s on my S6. I have a set of 16s on my Porsche too, and i really LIKE the steering feel of higher slip angles. It gives me lots of warning before bad things happen. On a track, that's very important to me.

note that aa light wheel also rides better. It has less inertia to fight the irregularities in the road, and is more easily damped by the existing dampers.

And furthermore, it creates less gyroscopic pull to fight -- and obscure -- steering. Not sure what I mean? Spin a bicycle tire fast and then try to twist the handlebars quickly. Hard, huh? As Colin Chapman said "keep adding lightness' He was right.

I will admit that on the nose-heavy S6 the 16" side walls (245-50-16, Z-rated all seasons) get a bit mushy. A previous ( but not round) set of GSD3s were better in this regard.

Grant

Just Me

BTW - they wont have a wider stance unless they are either a) wider wheels or b) have a larger offset.

Don't get me started about using the wrong offset. It messes up suspension geometry.

And the wider wheel goes half inboard ( and if it goes far, it hist stuff), and half outboard. SO if you go from 17x7 to 18x8, it is wider by 0.5", not by 1"

I agree they do look better that way. And lowered. Which, within reason, and if the car is properly aligned, improves just about everything except clearance - center of mass, squat, dive, weight transfer ( reason for the last 2) - and even looks. I generally look at 0.75 --> 1.25" below full stock. Audi sport are generally 20-22mm below stock already ( that's 3/4 inch, roughly)

Grant

2.7tDallas

Because engineers always want to apply simple formulas to extremely complex systems (like an automobile), with massive amounts of variables, in a very superior way, many times without the benefit of any real world experience with the specific situation in question

2.7tDallas

for wheel cost of $150 or less, you will not get great wheels.

You may be able to find some 18" factory wheels from an A6, S4, etc, with offset of 35 to 38, which will work fine, and usually be good wheels