What is the steer axle?

The steer axle is the front, steered axle of a truck. Federally it may carry up to 20,000 lb, but tires and the front-axle rating usually limit it to 12,000–13,200 lb.

The steer axle is the single front axle of a tractor — the one connected to the steering. It carries the weight of the engine, cab, and front of the vehicle, plus whatever the load transfers forward.

Its limit

As a single axle the federal cap is 20,000 lb, but in practice the steer axle is limited well below that by the front tires and the axle's own rating — commonly 12,000 to 13,200 lb. Overloading the steer axle hurts steering and braking, so it is a safety limit as much as a legal one.

A load whose center of gravity sits too far forward pushes weight onto the steer axle; shifting cargo rearward relieves it.