tire rubbing

i have a 1998 ford taurus with 18 inch rims. one of the rear tires was rubbing bad, it rubbed so bad that it made another lip in the tire. the other rear tire is fine. there is no more on one side than the other. could this be a bad strut, or something else???

it is on the inside of tire

i know that in some tauruses, the tire would rub on the inside, but only when hauling something heavy. it happend on the right hand side, and turned out to be the gas tank hose from the filler goes down at an angle and the rear splash guard rubs the inside of the tire. i'm not sure if that's anyhelp to you. goodluck