widest street tire?

[bmdoyle82]

I was wondering if anyone knows the widest tire that can go on a 2wd 2007 tahoe. I haven't lowered it yet but it does have the ppv package on it. Didn't know if 345 40 17 would fit on the back

 

[CrashTestDummy]

That's a lot of tire to put under that truck. Is there even 14" of space between the inner wheel well and the outer fender lip?