The tire manufacturers disagree about it fitting better at least, both BFG and Cooper list a 7.5” as the narrowest rim a 275/60/15 should be mounted on.
That said, I’m sure plenty of people have run them on 15x7’s. The problem will be that if the tire is squeezed on a narrower rim the tread pattern will be distorted, so you’ll have to run a lower pressure to keep all the tread on the ground. Otherwise it kinda defeats the purpose of running the wider tire.
