Off-Road tire testing presents a series of unique challenges for manufacturers and engineers seeking to evaluate their products in real-world conditions. These extreme testing environments demand a detailed assessment of a tire’s performance on challenging terrains like uneven surfaces, slippery mud, loose gravel, and steep inclines.
In this Q&A, we spoke with our experts—John McKinnon and Taylor Floyd—about what makes the Off-Road Testing areas at Treadwell Research Park the ideal place for real-world testing insights.
What are the common primary goals of off-road tire testing?
Off-road tire testing is fundamentally about ensuring a tire can handle the rigors of challenging terrain. A primary focus is on traction, which involves measuring how well a tire grips various surfaces like mud, rocks, and sand during acceleration, braking, and cornering. This also means testing the tire's ability to handle in mud or grip smooth rock faces. In addition, specific terrains are tested to ensure the tire is working as intended for its designed purpose.
Besides traction, durability is a critical aspect. Off-road tires must resist punctures, cuts, and abrasions from sharp obstacles. Sidewall strength is particularly important in these tests. Furthermore, evaluations include tread durability, to determine how long the tire will last under harsh conditions. While off-road performance is the core focus, on-road characteristics like noise levels, ride comfort, and handling are also considered, as many off-road vehicles are also driven on paved roads. Finally, the overall construction quality of the tire is assessed to ensure consistency and reliability.
Of course, the testing plan will vary based on the different types of tires being evaluated. R/T (Rugged Terrain), M/T (Mud Terrain), or A/T (All Terrain) tires can present different testing priorities. We work closely with each client to understand their final goals for the testing program to customize surfaces and maneuvers to provide the best opportunity to evaluate performance.
Are there any trends in off-road tire testing that you’ve noticed?
We've noted increased testing of R/T-type tires for both on and off-road performance, emphasizing cut and chip resistance, but also how the tires perform on paved surfaces. This speaks to an increase in the use of these types of vehicles on standard roads, which bring noise and handling expectations from consumers. We do still see plenty of emphasis on mileage accumulation on off-road surfaces to understand overall durability as well as traction performance (e.g. loose soil traction). Also, there has been a focus on evaluating chip, tear, and cracking over boulders.
What are the considerations for surface preparation and maintenance associated with off-road testing?
Consistency and repeatability in testing is critical to benchmark and understand performance differences. As you get into off-road surfaces, it can become challenging to create and maintain surfaces to allow for 100% consistency.
Every program starts with a conversation to better understand the testing goals. Before beginning a testing program, we will spend at least a day preparing the various surfaces to support the test requirements. This could include additional compacting of the surface, utilizing specialized surface grooming methods, or adding water to create mud, wetted rock, or puddle-laden surfaces. We also consider weather sensitivity and timing, going above and beyond to ensure everything is ready in advance of the client’s arrival on-site. During testing, we maintain continual upkeep of the track sites that may include grooming them after each test run to keep conditions optimal.
To maintain consistency with surface standards, we are actively developing new tools in collaboration with industry experts. Mud surfaces are an area that we’re actively trying to work with industry research organizations to study and develop ways to ensure consistency of surfaces for testing scenarios. By studying things like moisture content, soil type mixture of surfaces, plasticity, and liquid limits of different mixtures, we can better understand how to provide greater repeatability in surface preparation.
How is driver skill and experience factored into the testing process?
The selection of drivers is critically important due to the subjective nature of off-road testing. Approximately 90% of off-road testing is subjective due to the nature of the surfaces and variables involved. While there is certainly a lot of technical training involved in understanding tire technology and vehicle dynamics, there is also a large component related to the number of hours of experience that informs the driver with performance indicators.
We only work with internal team members and contract drivers who have the expertise to conduct test programs effectively. Additionally, we welcome clients to conduct their own evaluations with their teams of in-house drivers at the Treadwell Research Park.
What role does tire design and composition play in off-road testing outcomes?
Because off-road surfaces have such unique traits and variability, tire design and material selection need to be forgiving enough to accommodate a wide variety of conditions. Add to this the ability to also perform on paved surfaces, and companies are faced with a tall order.
The materials used in off-road tires are carefully selected to balance performance and durability. Tread compounds are a primary concern, as they directly impact grip and wear. Softer compounds offer superior traction on challenging surfaces but wear more quickly, while harder compounds extend tread life at the cost of some grip. Manufacturers also tailor compounds for specific environmental conditions, incorporating additives like silica and carbon black to enhance strength and resistance to damage.
Sidewall construction is another critical area where material choices matter significantly. Reinforced sidewalls protect against punctures and cuts from sharp obstacles like rocks or boulders, with ply construction playing a vital role in determining sidewall strength. Flexibility is also essential, allowing the tire to conform to uneven terrain and maintain traction. The internal structure of the tire, including belts and plies made from materials like steel, polyester, and nylon, contributes to its overall strength, stability, and load-carrying capacity. These materials are engineered to withstand the stresses of off-road driving, ensuring the tire can handle heavy loads and resist punctures, ultimately helping to determine the tire's overall performance and lifespan.
In addition to tire design factors, vehicle features provide another tool to properly validate tires. Some may require 4WD for certain terrains, while others can be tested with 2WD. Vehicles using axle-lockers can also be used for improved performance and real-life validation.
Different surfaces can be used to test the various design attributes of the tire. For example, tread pattern design and durability can be tested on embedded rock hill climbs as well as boulder crawls. On a trail ride, you can evaluate the performance of the tread pattern relative to traction and how it performs under surface contact with high lateral forces. Tread compound performance relative to traction can be evaluated under wet and dry conditions.
How can off-road testing contribute to innovations in vehicle design and technology?
The increase in electric vehicles (EVs) has created new variables to the testing of these powertrains on off-road surfaces. The added weight, different weight distribution, and higher torque at the wheels all contribute to unique performance in off-road conditions. We’ve seen more testing of vehicle stability as well as traction testing in various surfaces. Vehicle companies have also introduced special driving modes such as crawl or bounce mode to support performance in rough terrain.
Given the rapid changes to the market and technologies being developed, our off-road test sections are highly adaptable, allowing us to customize the track based on specific client requests. With ample space available, we can tailor the testing environment to meet the unique needs of each vehicle and scenario.
To learn more about our Off-Road Testing services or to discuss a testing project, Allison Ofenstein, Senior Operations Manager at
aofenstein@smithers.com.
