[SPYDERLK]

Adding mass to the tread area of the tire as these active balancing arrangements do, causes more energy to be lost as the tire flattens onto the road and resumes round shape as it rebounds. The tire deforms almost instantly as it contacts the road but is delayed a little in getting round again as it leaves. This hysteresis gives the effect of always running slightly uphill. A tire/wheel with weights on a non deforming area [rim] exhibits less of this effect owing only to the tire tread itself. This small effect repeated for forty million revolutions will end up costing several dollars in fuel over the life of the tire.
larry