Depends on the width of the rim. A wheel designed for the 700X20 may not work with the 900X20 as the wheel would be narrow and not have enough off set to keep the side walls from rubbing. If you already have 8.25's and they have plenty of space between them 900X20 should be fine. As old sub mentioned sidewalls rubbing can cause tire failure. Underinflation can also cause the sidewalls to rub.