Of course, but wider tires don't always = bigger contact patch. It depends on how much the wider tire crowns - go too wide and you end up with less contact patch and a tire that will wear out fairly quickly. No idea where the limit is on the stock Solstice rims, but presumably somewhere north of the 275x45 that gmtech said work well.To wspohn, yes, more contact patch will give you more grip...
BTW, in certain limited circumstances, a wider tire isn't always better. I've raced in classes that limit engine modification and any slight benefit you gained in cornering by going to a wider tire was more than offset by having to push that wider tire down the straight with limited power. I watched the other guys sticking on wider and wider rubber and going slightly slower and scratching their heads (they also got to the point where crowning became an issue for handling as well).
On an 18x8" rim, the normal maximum recommended tire is a 255x45, but one can usually push that a bit before crowning kicks in.
Sadly, all of my vintage high performance stuff has 15" and it is very hard to find any high speed rated tires in correct sizes for those any more!