Lug-type wheels are recommended for medium and heavy duty applications. For heavy duty use, the steel wheel hub is formed with a series of bubble-like indentations around the outer rim which match lug shapes molded in the compound of the semi-pneumatic tire. This arrangement prevents the tire from slipping on the hub.

Lug
Molded
Tires
Tractor tire with lug indentations molded into rubber to prevent tire from slipping on rim during heavy-duty use.