I think what he is trying to say is that if tires are mismatched, the smaller one will wear out in almost no time because centrifugal force will cause the smaller one to stretch to touch the road. This is why we use a caliper to match used tires on our trucks. One would think that the taller tire would wear faster because it carries the load, but it flexes like it was designed to do and wears normally. On the smaller tire, the carcass stretches abnormally and the tread is traveling less feet per second than the larger tires. Since the larger tire is carrying the weight, it gets traction and the smaller tire scuffs trying to keep up with the larger one. I have had drivers buy an old lug type tire on the road to replace a non repairable tire and mount it along side of an almost new shallow tread tire and the almost new tire is down to the wires in less than 500 miles. Its rather difficult to explain, but it is common knowledge to commercial truck operators.
For example, we set our ECMs for 513 revolutions per mile for low pro 22.5 drive tires. Low pro trailer tires can be about 516 revs per mile. If you do the math, you can figure how much the smaller tire will be scrubbed in 500 miles.
