What is the 3% tire rule?
The 3% rule states that when replacing tires, the new tire’s diameter should not differ from the original by more than 3%. This guideline helps maintain proper vehicle performance, safety system functionality, and speedometer accuracy. For your vehicle to perform at its best, your tires should all be of the same size, load-carrying capacity, speed rating, construction and tread pattern. The only exception to this rule is vehicles that rock a staggered fitment, which have different tire sizes on the front and back axles.
What is the 105% rule on tires?
Based on research performed by Silca, who observed an aerodynamic advantage when a rim is at least 105% the width of the tyre. This can be used to evaluate the setups, as well as refining riding pressures. Wider rims and tires offer tangible benefits in comfort, grip, and control, but they come with compromises in weight and aerodynamics.