Mismatched wheels

[Caleb Sykes]

How bad is it to have wheels of different sizes that are all powered together without any reduction compensation?

For example, say we have a 6WD drop-center drive with a 9" center wheel and 8" diameter wheels in the front and back.

My speculation would be that, as long as most of the weight is on the center wheels, you would lose the static friction on the front and back wheels, and have kinetic friction instead. The reverse would be true if most of the weight were on the front/back wheels. Since this arrangement would cause the wheels to slip more, wear on the wheels would also be a bigger concern than it would be for matched wheels.

Any theory or practical experience would be appreciated.