Influencing the track….

Axle ratings are posted on the door label. These values represent the maximum capacity for the axle, based upon the lowest rating of the contributing components. At times, this nominal capacity published for any single component can be influenced by the assembly. This is commonly true of hubs.

Aluminum and iron hub rating are dependent on the wheel offset, both on the steer and drive axles. Aluminum steer axle hub ratings can also be influenced by presence of a lift axle. Typically, iron hubs on steer axles are not affected the same.

The list of components which effect the rear axle rating are the axle, hub/drum, suspension, tires and wheels. Any one of these can reduce the rating. The key to overall rear axle ratings is of course the axle, but more importantly, iron or aluminum hubs coupled with wheel offset.

When specifying wide base wheels/tires (Super Single) on the drive axle, the offset makes a tremendous difference. It is important if changing wheels/tires on an as-built chassis to take these into considerations. The data below identifies the hub ratings for tandem drive axle sets.

• Aluminum using a wheel with 2-inch offset = 38,000 lbs.

• Iron using a wheel with 2-inch offset = 40,000 lbs.

• Aluminum using a wheel with 0-inch offset = 46,000 lbs.

• Iron using a wheel with 0-inch offset = 52,000 lbs.