Sorry for jacking your post i was i wanted to ask the same thing.

i have an 06 but rims from 08. I know the CR are 225/45-17, 255/40-17 i think. why is this.

Also as for my self i dont track but i take corners fast and do alot of spirited driving. so Should i go up to the 225/45-17, 255/40-17 over 215/45-17, 245/40-17. cornering means alot to me. im also looking at the same tires the Star Specs

 

CR tires are 215/45-17 front, 255/40-17. Why? Another small way to differentiate it from the non-CR, probably worth less than a tenth at the track...

Cornering means a lot to me too, and I roll on 205/55-16 front, 225/50-16 rears on the street. The benefits of wider tires on the street just aren't as dramatic.
215/45-17, 245/40-17
215/45-17, 255/40-17
225/45-17, 255/40-17
It really isn't going to make much difference. If you want slightly taller/wider tires, get them. If you want to save a few bucks, get the smaller sizes. No biggie.

 

Dunlop Direzza Star Specs.
225 F, 255 R.

Best bang for your buck out there.