[goatless]

Ummmm... you miss my point, Mr. Champ. Both 15" wheels and radial tires were available in 1964 and yet the engineers at Pontiac said your GTO would be better suited to have 14" wheels with bias ply tires. They must have had a reason. You have decided to go against those engineers.

Maybe if I put it in your own words you'll understand.

"I think the point that many are missing here is that just because a 15" radial tire can physically be mounted to a 1964 GTO doesn't mean you should or that it's safe to do it.

Car manufacturers have engineers that believe that 14" bias ply tires is what should be used for this car model.

I'm sure that there are good reasons for their belief."

Really, I'm just messing with you. I understand that ideally a 275 would be mounted on a wider rim. We make judgement calls every day regarding our classics, modifying them in ways the original engineers never intended or even imagined. Sometimes it's ok to step outside of the "rules" as long as you understand what is at play. As you can see from others that have posted above mounting a 275/60 on a a rim that is .5" narrower than the recommended range has very little negative associated with it. The worst issue that I've seen are the guys that pop up to tell you you shouldn't do that.