A car trailer axle is an axle that is mounted beneath a trailer designed to haul cars. Commonly arranged in a tandem configuration, a car trailer axle typically has electric brakes that are activated by a switch mounted in the tow vehicle. Commonly positioned by heavy leaf-spring suspension, a car trailer axle is fitted with multi-ply tires to allow the tires to support the weight of not only the trailer, but the vehicle carried on the trailer as well. The typical axle design for an auto transport is a straight tube axle with allocations for the wheel hubs welded onto each end of the tubing.
While there are single-axle trailers used successfully to transport automobiles, it is highly recommended that any trailer used for hauling an automobile be equipped with at least two car trailer axle assemblies. The tandem axle trailer uses four tires to support the trailer and the towed vehicle safely down the road, whereas a single-axle trailer uses only two tires to support all of the weight. Even with durable multi-ply tires, this is not a good arrangement. The single-axle trailer might be fine for towing a dune buggy or very light race car, however, it should be avoided for towing a full-size automobile.
The typical car trailer axle is long enough to allow the tires to extend out past the width of the trailer bed. This allows the vehicle being trailered to ride between the tires of the trailer, and be tied snugly to the trailer bed. Some home-built trailers use house trailer or mobile home axles on the trailer. The problem with using these types of components for a car trailer axle is the wheel attachment style. Unlike an automobile or car trailer axle bolt pattern that uses a regular automobile wheel, the mobile home axles use an open wheel that mounts by using lugs located at the extreme outer edge of the wheel.
The wheels used on the mobile home axles are difficult to install in an even manner, and they also come loose occasionally. By using a purpose-built car trailer axle, the wheels are much easier to tighten, balance and locate in the event of experiencing a flat tire. The tires typically used on most mobile home axles also are not intended to operate at the common highway speeds that a car trailer axle tire and wheel are designed for.