from what I have seen it depends on which tires as some 275's measure different not only in width but height also. Now the centerline of the tire will not change going to a 10" rim but the bulge on the tire will. A 8" rim will pull the sides a little more where as the 10" rim lets more of a flat sidewall if you know what I mean. Oh heck just get a bigger hammer also while your at it.

Top of the tire to where it goes in on the sides to the rim is more curved in on a 8" rim but as you widen the rim the side wall will be more of a 90* to the rim and this is the area you will have rub