ompanies have for years been developing aftermarket systems to further enhance the ability of, well, “adequate” leaf-spring suspensions to reduce the impact of road hazards on trailers. One of the simplest of these — from an installation standpoint — is SumoSprings, an “airless air bag” system developed by SuperSprings International.
It’s also one of the most technologically advanced products on the market. By using a closed-cell urethane — injecting nitrogen bubbles into the urethane — its proprietary design allows for the adjustment of the diameter and density of the air bubbles, effectively allowing the company to create products capable of different support capacities. It also features a parabolic spring curve, a fancy term for describing a progressive spring rate: as the suspension travels and there’s more movement, the SumoSpring gets stronger. It essentially functions much like an airbag system without requiring a compressor and can’t leak, making it zero-maintenance. SumoSprings are available in two densities for towable applications: “Blue” SumoSprings are designed for trailers with gross axle weight ratings (GAWR) of 3,000 to 5,000 pounds, while “Black” springs are for GAWRs of 5,000 to 8,000 pounds (superspringsinternational.com/trailer-sumosprings/). Kits, which retail for about $250-$300 per axle, are available for over-axle and under-axle leaf-spring configurations and can be installed in about 30 minutes. Kits also are available for a number of motorhomes and tow vehicles.
Before raising the vehicle, measure from the bottom of the trailer to the top of the leaf spring plate. Locate from the supplied parts a combination of spacer plates (0 to 2) that stick up to a height of ¼ to ½ inch taller than that initial measurement. Then, using the correct length 8mm bolt (supplied), attach the SumoSpring to the mounting bracket, adding a light amount of Loctite to the bolt threads. Leave the connection loose for the moment.
Secure the trailer and raise the frame high enough to position the SumoSprings on the leaf spring. Place the SumoSpring perch on the leaf, ensuring it is positioned between the U-bolts attaching the leaf spring to the axle.
