A 15x7 is the minimum recommended width from the manufacturers for a 255/60/15. The manufacturers measuring rim width is only 15x7.5” though, and the tread width is usually ~8” to 8.5” depending on which tire you’re talking about.
Obviously there are some tire shape differences between the minimum recommended width and the maximum recommended width. But as long as you’re still in the manufacturers recommendations you really shouldn’t have any issues. Maybe some tire pressure fine tuning for the track, but even that should be minor.
Based on the number of people here that completely ignore the manufacturers recommended minimum and maximum width and raise holy hell about how they’re not dead any time I say something about not doing something stupid like ignoring the minimum rim width recommendations I’d say you should be fine if you follow the manufacturers guidelines.
