here’s an old adage among some veteran RV owners that notes that the first rule of camping “is to fix what may have broken on the way there.” It’s obviously an exaggeration — contemporary RVs are built to higher quality standards today, and both manufacturers and dealers have implemented extensive pre-delivery inspections to catch most problems that may have crept into the assembly lines. That said, as RVs age they do tend to experience higher component failure rates; it’s an unavoidable aspect of towing mobile houses across untold miles of suspect roadways.
This is especially true of travel trailers and fifth wheels, which rely on leaf-spring suspension systems. There’s a reason for this: the suspension works, its simple design makes it inexpensive to use and it can be easily adapted to virtually any towable design. But while the venerable design does help to mitigate the terrain, there’s only so much a simple multi-leaf spring pack that’s bolted to the vehicle frame and axle can accomplish.
Not surprisingly, companies have for years been developing aftermarket systems to further enhance the ability of 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. Founded in 1998, the Carpinteria, California-based company released a version of its SumoSprings for RV towables in 2019 — and, to underscore its confidence in the system, SuperSprings International offers a no-questions-asked 30-day moneyback guarantee on the product. Since January 2020, said Adam Weisner, chief commercial officer, SuperSprings International has only been asked to honor the guarantee five times, “Or about 0.001% of our Trailer SumoSprings sales.”
The performance of SumoSprings has also led to the product being installed at the factory by a number of RV motorized manufacturers, including Winnebago, Tiffin, Coachmen and Midwest Automotive Designs, and SuperSprings International is in talks with towable manufacturers to have them added as factory equipment. The company has also approached a number of dealers, including Fort Worth, Texas-based United RV, which now equips all trailers with Trailer SumoSprings before releasing the units to customers.
To understand the popularity of SumoSprings requires a bit of background on how it came about — and what it really is. The company’s first product, SuperSprings, was initially developed by the sister of SuperSprings International CEO Gerry Lamberti in South Africa. Lamberti bought the patent and set about developing a product line for what he characterizes as a “mechanical spring.”
“I was looking for a closed-cell urethane where effectively, instead of the air being in a single-volume airbag it would be in a urethane matrix of nitrogen bubbles and urethane,” said Lamberti, who is an engineer. “Technology perfected in Germany had allowed micro-cellular urethane to be formulated so you can adjust the diameter and the density of those air bubbles. With that technology, we could not only create an ‘airbag’ at various air pressures, but in a urethane matrix — which would allow it to not rely on a compressor. And by being closed-cell, it would never leak.”
The stumbling block, said Lamberti, was that he also wanted the product to have a parabolic spring curve, which is essentially a product with a progressive spring rate. Once that was accomplished, he turned to one of SuperSprings International’s major clients, the U.S. Border Patrol, to test the product.
“It was a great testing ground because they sometimes have to drive those trucks like they stole them, across extremely rough desert terrain,” Lamberti pointed out. “And SumoSprings withstood that kind of punishment. It was durable and it gave a great drive quality.”
Proven at the Proving Grounds
According to Weisner, SumoSprings have performed just as well since their release to the RV market — but the accolades have always been seat-of-the-pants observations. To understand exactly what Trailer SumoSprings delivers in the areas of ride quality, SuperSprings International executives and technicians spent time recently at the Navistar Proving Grounds in New Carlisle, Indiana. The expansive site —used by an array of vehicle manufacturers — includes a three-mile oval and specialized grades on- and off-road designed to evaluate vehicle suspension dynamics. The oval also was used to simulate the forces on the trailer when being passed by a truck moving in the opposite direction.
“Navistar has developed an extensive array of testing equipment, including 7-way gyroscopes and accelerometers, that can monitor everything the suspension does,” said Weisner, who added 32 remote cameras to the interior, exterior and beneath the Grand Design fifth wheel to further document the testing.
The testing itself was done using a 2020 Grand Design Momentum two-axle fifth wheel with an unloaded weight of 14,000 pounds, pulled by a Ford F-250 truck. The truck and trailer made numerous passes through each track segment in stock form to establish a baseline, then replicated those tracks after the installation of SumoSprings to gauge improvements.
Once collected and analyzed, Weisner said the data provided an eye-opening glimpse into how a typical trailer suspension reacts to road irregularities — and how such forces were significantly canceled out by the addition of SumoSprings to the suspension.
The “spike” Weisner referred to was a large event — in real-world use, comparable to hitting a pothole or crossing between the curb and roadway when entering a driveway.
“Spring-leaf packs are not really made for spike loading, so it’s a very difficult problem to solve,” he added. “But as the suspension travels and there’s a lot more movement, the SumoSpring gets stronger. It pushes back more as more pressure is applied because of its parabolic spring curve.”
From Weisner’s perspective, an even greater benefit of SumoSprings was the product’s demonstrated ability to lessen the G-forces that act on the trailer.
And, as Weisner pointed out, the performance of Trailer SumoSprings doesn’t come at the cost of compromising any other suspension component.
“SumoSprings complements the suspension versus replacing it,” he said. “And it’s maintenance-free. We’ve done torture tests you can see on our YouTube channel on the product where we drilled holes in it, we threw it in a lake, we set it on fire — and then we put it back on a truck, put a few screws it and then ran it. And performed just the same. It can withstand the elements and extreme use, which is perfect for the outdoor industry.”
