Are you thinking of installing a tire with a 9" tread onto a 7" wheel?
Or one with a 9" profile?
Cuz, a 9" tread will have a profile about 1.5 inches wider, so say 10.5, which translates to about 267, which rounds up to a 275. But, a 275 on a 7" rim, at normal tire pressure, will pull the edges...