[Kevin Sevcik]

You'd kill your battery pretty quickly. Driving straight forward, the motors would have to provide enough torque to overcome the static or kinetic friction of the wheels you're slipping. Even without much weight on them, the outer wheels will take a decent amount of torque to slip like that.

I think the reason it works in the case of slight differences in diameter is because there's enough give in the carpet-tread system, that the tread and carpet just elastically deform to accommodate the differential as they roll from starting contact to full contact to releasing contact. The incoming tread and carpet is always undeformed, so it's not like there's any build up of differential. Elastically deforming the tread and carpet for that little bit still requires some force, but it's almost certainly less force than sliding friction.