Tires on the front axle of any spread axle trailer can be exposed to fairly severe service, and even more so on drop-deck spread axle trailers.
When designing a tire for a drop-deck spread axle trailer, creating a product to withstand the demands of the application is challenging. Tires in this application are among the most abused of any in the trucking industry. When the Cooper Tire engineering team set out to design a Roadmaster tire that could take the punishment that carriers dish out, their goal was to develop an excellent tire at an affordable price.
For several months, the team used computer modeling and advanced finite element analysis to test various ideas for tire shapes and structures. They also evaluated various tread compounds for their ability to withstand the enormous lateral pressures the tires endure.
3,000+ Lbs of Lateral Force
When trucks pulling spread-axle trailers make a turn, an enormous amount of force transfers from being distributed across a tire’s total footprint to being focused on its shoulder rib—up to 3,000 pounds of lateral force. A tire that’s not designed to handle this kind of abuse can experience significant damage.
The forward axle on a spread-axle trailer is typically 10 feet from the back axle in order to spread the weight of the load more evenly. As the trailer turns, it pivots on its back axle and, as a result, the tires on the trailer’s forward axle scrape along the ground (scrubbing) sideways. tranferring as much as 60% of the 5,000 pounds that the tires carry. This loading and scraping can potentially tear the shoulder rib.
With all of this in mind, Cooper engineers set out to develop the Roadmaster RM272 so that it could handle the stresses of spread axle trailers as well as the more routine scrubbing and curbing which can cause tires to find their way to the scrap pile quicker than their long-haul counterparts. That’s why having a tread compound that provided the best balance between resistance to side forces and optimum wear was important for the RM272.
Tough Test Procedure
As the Cooper engineers developed some options for the new Roadmaster RM272 trailer tire, they knew testing would be difficult. For a spread-axle trailer tire, the tire industry has no standardized test that can adequately simulate extreme conditions under which spread axle trailers operate.
Applying several different test protocols at commercially available test sites, Cooper engineers were not able to replicate the conditions they had seen on some tires returned from the field. So the engineers developed proprietary testing procedures and built a small test facility that could adequately simulate the range of road conditions.
The rigorous testing provided all the stresses and forces found in the worst conditions one could expect to see in the field. The tires were dragged under full loads across each of the test surfaces to simulate the dragging they would experience out in the field maneuvering in tight quarters. This helped achieve the goal of designing a tire that performed above the call of duty in this tough service and yet still retained the capability to be used in all positions.
The resulting Roadmaster RM272 has a slightly rounded tread footprint, along with a reinforced shoulder, to help withstand extreme side forces and the scrubbing and tearing that spread-axle trailer tires can experience in everyday operating conditions. Like all Roadmaster tires, casing integrity is an important element. All Roadmaster tires are engineered for retreadability and are backed with a strong warranty of two retreads within six years.