Originally Posted by +fireamx

I guess I should have elaborated a little more when I mentioned the 11 year old Motor Trend article.
The 03 SLK was mechanically identical to the 04 Crossfire. H.P. and gear ratio.
Speedy 4x4 clarified what I meant by saying the SLK had smaller wheels, this is how Motor Trend put it.

From the starting line, the SLK showed a slight acceleration advantage, which increased throughout the run. The Crossfire is about 100lbs lighter overall, but its wheels are much more massive, creating more rotating inertia.

Those very same "smaller" tires that help improve the 0 to 60 (and 1/4 mile) times of the NA SLK over the NA Crossfire, may just have a detrimental effect on the "Supercharged" version of the SLK. Because the smaller width of the 225/50/16" tires don't lay down the footprint of the Crossfire's big meats.