https://www.zytrailerparts.com/products/trailer-rear-axle/ Trailer Rear Axle is the most important part of a trailer. It's root mean square rating is determined by its axle beam and tires, but the actual load is more a function of your vehicle's weight distribution. The reason for this is that the majority of weight is transmitted to the axles via your vehicle's frame. For more trailer axles and springs at bulk price.