Tandem or dual axles, usually found on big trucks, are a pair of axles holding two sets of wheels closely spaced together, with a shared suspension. “Tandem” is defined as “having parts arranged one behind another.”
Axle load limits define the amount of weight that an axle can carry, including the weight of the entire vehicle. Axle load limits ensure the safe transportation of truck cargoes, given the effect of axle and tire loads on bridges and pavements.
Tandem axle centers are 40 to 96 inches apart. Tandem axles connect independently to or have a joint attachment to the vehicle. A mechanism linking the axles balances the load between them.
Haul or towing capacity determines the upper limit to the trailer load that a vehicle can haul. In the United States, the federal interstate system tandem-axle haul capacity is 34,000 lb.
