What a nice set of many different wheel and tire configurations in this thread. I know the OP asked for thoughts beginning at 245 wide tires. I am fine with that, and although I fall into a lesser range numerically, I think visually I strike a balance that takes into consideration the positive impact of less unsprung weight on both handling and acceleration. On both our 1969 Shelby GT500 and our 1973 Mach 1, we are using Magnum 500 15 x 7" wheels (I believe original on only the Shelby, added later with the Mach 1 which were originally E70 x 14 bias ply tires). They are now running with 235R60 x 15 tires radial tires on the Mach 1, and old school reproduction Goodyear Polyglass GT F60 x 15 bias ply tires on the Shelby.
Now, at this point I will be the first to say the Shelby handled far better with radial tires on it. I intentionally found a set of reproduction Polyglass GT bias ply tires because that is how the car initially came when new, and I wanted to stick with a high degree of conformity to the original vehicle - just because. That said, when the day comes the Shelby needs new tires I will select a nice set of radial tires for it in P235R15. I have heard that there is one reproduction tire now offered in a radial version of the Polyglass GT. If so, that is how I will go. If not I will look for the best radial tire suited for the Shelby.
Anyway, I found long ago that as nice as wider tires are for traction, especially with TractionLok/PosiTraction, it is possible to over-do a good thing. The larger tires, and wheels, bring to the table higher weight. Weight in the wheels and tires wreak havoc on overcoming inertia when beginning to spin the powertrain up in motion. And, when it comes to handling, less unsprung weight is always better than more unsprung weight. I, admittedly anecdotally, feel anything larger than G60 x 15 (or radial equivalent P235R60 x 15) is beginning to push into the area of more unsprung weight than I wanted to have to deal with. That said, the F60 x 15 tire on the Shelby is akin to a P225x60, a little smaller than the P235R60 tires on the Mach 1 that originally came with 14" wheels. Long ago I ran with a set of a friend's G60 x 15 wheels and tires on my 1969 Mach 1, and the inner fender & quarter metal rubbed/cut into the outer parts of the rear tires. I have not had any issues with the F60 x 15 tires on the Shelby. It is possible G60 x 15s would be fine on the Shelby, but I opted to err on the side of caution. They still look plenty meaty and do good job keeping me planted on the pavement. I will more research on fitment before replacing the tires on the Shelby, and if I can get away with P235R60s that is what I will get.
So, finally, we got to the end of this post. If nothing else, the tires and wheels on out 69 Shelby and 73 Mach 1 look great, and handle well. Although I do not track these vehicles, nor pretend to track them on public roadways, I can tell what works well both aesthetically and with real world performance. I qm a happy camper.
