There are many reasons for variations in tire wear, but they can be broken down into two basic categories: Driver behavior and hardware/environmental factors. To summarize the first, driving practices that maximize fuel economy also tend to extend tire life. Putting aside high-speed cornering caused by lack of brake application and over-inflation to minimize rolling resistance, this is a reasonably valid correlation.

Now let's focus on how equipment differences can affect wear patterns. Radial truck tires, for example, are designed to operate at specific load/inflation relationships for optimum wear. So tires that are either lightly loaded or overloaded will wear faster. Why? Because the pressure distribution designed into the footprint area at the tire/road interface is disturbed if the tire is under- or overloaded.

A light load has a greater impact on treadwear than does an overloaded condition, which has a greater impact on casing durability. How does this affect tire wear in vocational service applications that include diminishing loads — or the ultimate load variation, light tare weight tankers? Assuming tires are properly inflated to carry the full GVWR of the vehicles when loaded, it's likely that more tire wear occurs on the empty return than on the outbound, loaded leg.

Assuming that the load/inflation relationship is correct, what are some other factors that can influence tire wear? Cornering forces, such as experienced by steer tires, as well as torque applied through drive tires, cause faster wear rates than experienced by non-steering, free-rolling tires, e.g., trailer, tag, and pusher axles.

However, those forces also tend to “clean up” developing irregular wear patterns. Wear rates on a typical tandem drive 18 wheeler would be fastest on the drive axles, moderate on the steer axle, and slowest on the trailer axles. The onset of irregular wear would normally be in the reverse order.

Since tires with deeper tread depths tend to develop irregular wear sooner than shallow treads, this has led to axle-specific treads for high speed rigs: 18-19/32 for steer tires; 24-30/32 for drive tires; and 12-14/32 for trailer tires.

Wheelbase is another factor, especially on tandem drive trucks. Since the steer tires must generate sufficient cornering force to slide the tandems in turns, shorter wheelbase trucks tend to wear steer tires faster. This difference is most pronounced in service that requires a high frequency of and/or severe wheel cuts. So trucks with steer axles that have a higher-angle wheel cut capability, while more maneuverable, tend to wear steer tires faster.

Steer tires on tandem drive axle vehicles usually wear faster than those on single drive axles. This is true whether or not the “drive” axles are truly driven or are merely tag or pusher designs.

On light-duty vehicles with idler-arm-type steering linkages, right side steer tires usually wear faster than left side tires due to the less polished, more abrasive texture of the road surface near the shoulder.

On medium and heavy-duty trucks with solid beam axles and drag link mechanisms that connect the steering box pitman arm to the left steering knuckle, however, the road surface effect is overcome, and the left tire typically wears faster.

Drive tires of single-drive vehicles wear faster than tandem drive counterparts in response to the difference in torque being transferred by each tire. Thus, higher torque engines wear drive tires faster, and small- and medium-duty trucks with diesels engines wear drive tires faster than those with gasoline engines.