Since tires represent such a large expense for truck operators (normally the second largest non-labor cost behind only fuel), considerable thought is given to tires of the future; specifically, on ways to improve operating efficiencies influenced by tires. I’d like to share some admittedly subjective thoughts, based on my 50 years spent in this area.
First, there is a growing difference between high-speed linehaul and mixed service (on/off road) and local P&D tires. Special tread rubber and sidewall compounds resistant to rock cuts, stone drilling and other abrasion type injuries characterize mixed service tires. Thicker sidewall gauges and deeper tread patterns also enhance traction on deformable surfaces and extend casing life by allowing fewer belt and ply cord injuries.
In recent years, the extreme loads, constant severe acceleration/deceleration and scuffing of sharp turns in congested service routes have favored larger sized cross sections, higher load ranges and inflation pressures, and even special heavy-duty fastening systems for these workhorse axle end components.
Meanwhile, high-speed linehaul tires have evolved in a different direction, with lower rolling resistance compounds, lower aspect ratio (height/width) dimensions, slower-wearing, quieter and more irregular wear resistant tread patterns that are compatible with softer riding, and dampened air suspension systems on drive and trail axles. The biggest game changer is the introduction of even lower aspect ratio wide single tires, now available from multiple tire manufacturers, designed to replace traditional dual tire fitments.
From an engineering perspective, it is logical that all pure over-the-road, high-speed trucks will eventually adopt this technology. The basic structure of two supporting sidewalls instead of four on an axle end favors lower rolling resistance and results improved fuel economy, which will become more evident as new single tire technology continues refinement. This, combined with substantial weight savings, will make the choice of singles replacing dual assemblies inevitable.
Future mixed service tires, on the other hand, are likely to remain on dual assemblies, especially in applications where casing damage is frequent and less expensive versus wide single tires. Also, P&D and other less fuel sensitive operations can be expected to take advantage of a new secondary (retread) market for worn out linehaul steer tires once more drive and trail axle positions are converted to singles.
This creates the dilemma of unique linehaul steer axle tire sizes with no opportunity to use these casings, once retreaded, on drive or trailer positions.
One option would be to sell steer tire casings after their first treadlife to fleets still running duals or to an alternative downgraded market such as local P&D, export, farm or local delivery service. A more productive, cost-efficient solution might be to utilize high quality retread processes and materials that assure properly inspected casings could serve a second treadlife on steer axles. This is currently done on many mixed service and local P&D highway trucks now. The only legal restriction is that retreads cannot be fitted to passenger carrying vehicles (e.g. buses). However, retreads are not generally used on steer axles of high-speed trucks, as new tires are fed first through steer positions and ran as used or retreads to the remaining drive and trail positions not yet converted to singles.
Further, if used linehaul steer tires are not programmed to serve later on other axle positions, why not consider using smaller diameter, lighter weight, more fuel-efficient, tire sizes? For example, the smaller 19.5-in. steer tires currently growing in popularity for height conscious car hauler truck/trailer combinations could be used on any linehaul Class 8 tractor. This would lower the truck chassis, resulting in a proven aerodynamic drag improvement from reduced under chassis to ground plane space with smaller add-on front air dams.