What makes an R/T an R/T? Well you got all the technical stuff thats been listed here already but the main difference, the thing that separates the R/T from all the other RAM's out there is fact that there is a different hot chick in the passenger seat every weekend who wants a ride in a very badass truck and then wants to ride something else....
And yes diameter of the tires is the same as any other ram. I checked this when I did an alignment on my truck. I didn't want to put the alignment heads on my rims so I borrowed a 2009 ram off the used car lot where I work which had 17" rims on it and they measured out to be the same exact diameter.
My rt looking sexy with 17's: