Right now I have 225/45/17 tires on my 17" american racing rims. I'm going to buy some Nitto 555R drag radials. What would fit? I'm assuming the 225/45/17's would(obviously) but what is the biggest I could fit, because I would REALLY like to get 315s. I wouldn't mind getting the 275 either...

 

It would help if you'd provide the width of your rims, though with them having 225's right now im going to bet for some unknown reason you bought 7" wide rims, if this is the case you have no chances of installing 315's on them, slim to none for 275's, and probably the most you'll get away with is a 245.

 

I have no idea how wide my rims are...how do I check..i bought the car this way..

 

Try removing one and look at the backside of the spokes and or in the lugnut area it may be there on the wheel. If not you'd have to get the tire dismounted and check, honestly though, your gonna need new rims to run even 275's.

 

Does it even really matter how wide I get my tires?? The Nitto555r 225's would hook up just as well wouldn't they? or the 245's

 

Too wide of a tire on a narrow rim will actually give you less traction than a narrower tire.