[fredjacksonsan]

Yeah, should have claridied; I was referring to a big change in size, as generally a little bigger won't bother anything. But if you go from 225/75r15 to a 33" tire, that makes a big difference. On one vehicle I had, (ok it was a car) I went from 205/70r15 and 25mpg on highway to 225/75r15 and 17mpg highway. Guess it depends on the vehicle.....