id like to know if anybody can let me if245/40/19 tires will work on a crossfire

 

on the rear, yes...

 

I wouldn't see why not I have 265/30/19 on the rear of my N/A and the installer never mentioned an issue. Or are you more worried about the being to small for the wheel?

 

Should work.

If you go on Tirerack.com and find your tire, you can pick the 'other sizes and pricing' tab next to the 'product description' tab and then locate the correct tire size.

Upon selecting the tire there is a tab that says 'Specs', and under that tab it tells you the Rim width range. For instance, the brand of tires I am currently running (Hankook Ventus V12 Evo K110), in 245/40/19 fits a rim width range of 8-9.5". I believe our OEM rear rims are 19x9, so those tires would fit.

Here's the link: Hankook Ventus V12 Evo K110 245/40ZR19

 

Many are running 275s and more without an issue. I have 255/30/18s (race slicks) on the front, much can be done than the factory settings. Woody

 

+1, my rear tires are 275/35/19

Everything is totally stock (OEM rims, suspension, etc.)