Originally Posted by footie
Why do you believe 20" will be better?
The facts are that the large the rim, the smaller the side wall and with it the ride gets worse, the transition from grip to slip is less predictable and the steering feel is unpredictable with increased tramlining.
Try an M3 with 20" and then try one with stock 18". If you think the 20" still feels better then you are the type of people that 'show' is more important than anything else.
Try and follow my logic and math posted above if you want an answer to your first question. I don't necessarily think that 20's will perform better except that I can't see why they shouldn't from what I stated above. I don't even necessarily disagree with the sidewall argument except that there are cars much faster than my E92 M3 that run 20's stock or use sidewalls that are lower profile.
I'm about to purchase a new set of rims and I'm curious why everyone seems to agree that 20's perform worse because they're heavier when in my example they clearly are not. No matter what I decide to do I'm keeping my stock 19's for track work. On the track I completely agree that function takes precedent over form. You don't have to look pretty as long as you get the job done. On the street, however, I would argue that form "could" take precedent over function since you shouldn't be taking the car or the tires to the limit of their abilities. Racing is for the track.
Once again, I'm not sold on 20's nor do I firmly believe that they will perform better OR worse than 19's. I'm simply trying to answer a question that has been bothering me.