A used trailer axle may be an economical answer to a damaged or otherwise incapacitated trailer, but you will need to do a bit of research to find the right one. A visual inspection will certainly be necessary to ensure the used trailer axle is in good condition, and you will need to know the fair value of such an axle to ensure you pay the right price. Keep in mind that axles vary significantly in size and function, and you will need to find out what size and weight capacity you need for your trailer.
The weight capacity is a number that dictates how much weight can safely be placed upon the axle without causing it to fail. This number may be imprinted on the axle itself, or it may be simply determined by the manufacturer. Be sure to take note of the weight capacity of a used trailer axle before you purchase it to ensure it will work properly with your trailer and support the amount of weight you are likely to haul on a regular basis. The width of the axle will also be important to note, as a used trailer axle that is too narrow will not work on some trailers, and one that is too wide may not be street-legal.
Consider the added options you need the used trailer axle to have. Some axles feature leaf spring suspension systems, while others may simply be dead axles without suspension at all. In general, if you will be driving the trailer over rough terrain or will be towing items that require a smooth ride, you will need suspension. Heavier loads will also benefit from adequate suspension. Some trailer axles will also feature some sort of braking system that works in conjunction with the wheels; this braking system is activated at the same time as the brake system of the towing vehicle, and if you need such a system, you will need to research to find out if it will work with your make and model of towing vehicle as well as the wheels and trailer chassis you intend to use.
When visually inspecting the used trailer axle, look for obvious signs of damage or neglect. Rust on a steel axle is quite common and not necessarily detrimental, but rust that leads to holes or cracks can compromise the integrity of the unit. Look for cracks, holes, dents, or other damage that can worsen over time, and be sure to inspect any bearings or moving parts carefully to ensure they are not seized, loose, or otherwise in poor working order.