Independent wheel suspension

The rubber torsion axles have advantages and disadvantages. The advantage is that the give a real good ride when they get about 60% or more of there rated weight on the axle. The disadvantage is that they need to be replaced every 20 years or so because of the rubber getting hard. Also since they don't have an equalizer, they must take the entire load on one axle (assuming you have tandem axles) if the bump is high enough such as large speed humps. Some rubber torsion axle manufacturers require each axle to be rated at 1.25 the intended maximum load because there are no equalizers. Flexiride is the one one that I know of that has adjustable torsion arms with spines. I won't buy them any other way.
Dexter made independant leaf spring axles that were used on Avions during most of the 1980s. These axles give a good ride and are great for towing. Eventually, (late 1988) Avion went to rubber torsion axles because they were cheaper.