Tire Force Variation

A tire may normally appear to be a true circle with a uniform internal structure. However, due to the construction characteristics of a tire, the tire's weight, its' internal rigidity, and its' dimensions, tires may have a small amount of variation.





Force variation should not be confused with out-of-round tires or tire imbalance. In fact, tire force variation cannot be determined by the naked eye or most types of balancing equipment. Tire force variation can only be determined by setting a tire on a drum, applying a load to the tire, and then rotating it while the drum axis-to-tire distance is kept constant. While the tire is rotating, the variations of reaction force that cyclically develop on the ground contact is measured (Figure 1). High force variation can contribute to a vehicle surge/vibration.

NOTE:
PENTASTAR TIRE BALANCER H-9702-DD-R (HUNTER GSP 9700) HAS THE CAPABILITY TO MEASURE TIRE FORCE VARIATION.