Radial Force Variations
The radial force is a force that compresses a tire. Based on its size, a tire has softer (-item A- ) and more rigid areas (-item B- ) due to design and production-related factors. Given this, the tire compresses to various extents at a constant wheel load (-arrows 1- ) and a constant tire pressure (-arrows 2- ). This varying spring action (-X- ) in the tire can cause vibrations in the chassis on even road surfaces and the driver may notice this as shaking in the steering wheel, for example. Measuring the radial force variation involves running the tire on a wheel balancer that measures radial force variation while applying a constant load to the tire. This simulates the rolling of the tire on a driving surface. Variations in radial force occur independently of the direction of rotation of the tire and are measured as the difference between the maximum and minimum radial force ("peak to peak" value).