I am on the same page with anyone wanting to control cost's when doing mods. However, their are some area's where you should pick carefully or you can pay a price in your ownership experience. When buying rims, do be carefull not to let their weight go too much higher then the oem rim weight. Your oem suspension will only be able to contain and control so much more unsprung weight and not have that increase felt ride and drive wise. Some will focus on rim weight and rotational mass, but that's not really my reason for posting.

 

It's my understanding that the coupe's sport suspension ('03-'04 coupes with forged 18" wheels and '05 coupes with forged 19" wheels) was and is stiffer than the sedan's sport suspension.

Dropping the ride height by 1/2" without changing the spring rates will increase the chance of the suspension bottoming-out. You might be able to leave the shock valving the same but the spring rates would most likely have to be increased to keep from hitting the bump stops. Even a 1/2" reduction in ride height is a big difference when considering the total amount of suspension compression.

However, it's obvious that you've been around a lot longer than I have (based on your number of posts).

I do completely agree with you on the quality of wheel that someone should consider. You get what you pay for and a set of wheels is not something one should skimp on. Most people don't realize the affects of increasing unsprung weight, sometimes beyond what suspension engineers accounted for, and the ill effects is can have on a vehicle (not only for performance—accelerating, stopping, and turning—but for safety as well). Not to mention the added rotational mass and increased rolling resistance of a wider tire (going against Pontiac's old motto, wider is not always better).

 

the avon tech m550 is what i just put on my car, and they are very nice tires. they are good in the wet and dry and ride so quiet and smooth, you hardly know they are there! they are not as grippy as the firestone firehawk wide ovals i took off, or the michelin pilot xgt z4's i had, but they do not grip any less. they just don't feel as grippy. of course i had 235/50's vs the 215/55's i now have on, so that had some influence i'm sure. also, the stock size 215's are giving me an average of 2mpg better than the wider tires. it may not matter to you, but i thought i would mention it.