Plus sizing is one of the easiest ways to achieve enhanced performance and improve the appearance of your vehicle. In the example below, a 15x7 wheel with a 205/65R-15 tire is considered the O.E. (original equipment) size. Converting to a plus one size would mean increasing the wheel diameter by one inch (16x7.5) and selecting an appropriate tire to fit (225/55R-16). Likewise, moving to a plus two fitment would result in a 17x8 wheel and a 245/45R-17 tire. It is important to note that although the wheel diameter is increasing, the overall diameter of the tire remains consistent.
Two things happen to the tire to increase performance when moving into plus sizes. First, the tire becomes wider due to an increase in section width. This provides a larger footprint and more contact with the driving surface. Second, the aspect ratio is lower, resulting in a shorter sidewall. The combination of these changes offers better lateral stability and increased steering response.