Increase in Wheel Diameter
Plus sizing is one of the easiest ways to achieve enhanced performance and
improve the appearance of your vehicle. In the example above, 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.
Increase in Section Width
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.