During road operation, the trailer, at the tractor connection, tends to ride up and down. This causes tire bounce on both the drive and steering wheels of the tractor. The tires are continuously being compressed, a condition that eventually leads to tire cupping. A lightly loaded rig will tend to bounce and shake, a condition that is not only hard on the tires, but all mechanical parts and assemblies. You have probably noticed this most when passing or trailing an empty tanker-not only the violent shaking but the noise.
Hard trailer braking, causing tire bounce and vibration, leads to further tire wear.
The reader can probably think of others. Any condition that might change the weight distribution of the tire over the miles and years of driving will not be corrected by static wheel balancers. Before getting into that, let's find out just how they work and how many different types of active wheel balancers there are. All of them mount so as to turn with the wheel assembly. They are usually in the form of a round metal plate mounted in some manner to the wheel assembly, with a tube filled ball bearings, shot, sand, oil or mercury forming a ring around the outer perimeter.