Will Lug Tires Remain a Driving Force?
Remember the days when nearly all car owners except those in the southernmost states ®“ performed the ritual of mounting and removing snow tires each year? Many drivers even purchased separate wheels, dedicated for use during the winter to avoid the extra time and expense of the semi-annual mount/dismount routine.
While some may still adhere to this operation, most notably emergency service vehicle operators and those hearty souls who reside in heavy snowfall areas, many mainstream motorists have abandoned the practice in favor of all-season type tires.
What has caused, or more appropriately allowed, this change?
First, roads in North America continue to improve. We’re not talking about the need for pothole repairs here and won’t get into the orange barrel discussion. Facts are that maintained paved roads continue to grow as a percentage of total roads, and the average motorist spends a greater portion of driving time today on limited access highways vs. crowned secondary roads.
Increases in population density and urban sprawl boost tax revenues, and also increase demand for timely snow removal and chemical treatment of more heavily traveled roads.
Secondly, vehicle configurations have changed with a large portion of the mix now made up of front-wheel drive passenger vehicles, and many four-wheel drive SUVs. These all have improved driving traction. Granted, two-wheel drive pickups remain popular, and while they have handling and winter traction characteristics similar to older nose-heavy rear-wheel drive autos, many are second or third vehicles in multi-car households.
From the Old to the New
Perhaps an even more significant factor is how automobile tires have changed. New generation rubber compounds that allow treads to remain compliant in cold temperatures, and CAD-generated tread designs that optimize tread pressure distribution and tread element phasing without the added noise and vibration of the old “snow” tires, have truly advanced the state of the art. Many tire engineers confirm that it’s difficult, if not impossible, for average motorists or even vehicle enthusiasts today to predict winter tire traction performance based on visual appearance of the tire tread.
For these and other reasons, lug-type drive axle truck tires may be prime for an evolution. In fact, some tire manufacturers already offer the first round of new hybrid designs that feature closed shoulders, but retain discontinuous center ribs and deep tread depths.
Some were designed to address compatibility issues with air suspensions on tandem drive highway tractors, which can result in uneven wear and premature removal of some older traditional tread designs with shoulder lugs.
Fleets Experiment With Ribs
Prior to the availability of these new tires, some fleet operators experimented with steer axle-style rib tires on drive wheel positions and reported significant fuel economy improvements and improved (softer) ride with less high-frequency vibration, especially noticeable in sleeper compartments.
Some also report more responsive handling, although this hasn’t been a big issue for large over-the-road trucks. The biggest downside reported by operators using rib tires on drive axles has been a removal mileage shortfall, especially in high torque applications like heavily loaded single drive axle rigs. Rib tires also generally deliver good driving, braking, and lateral traction on wet and dry paved surfaces. This leaves only soft or deformable surface conditions, such as mud or significant snow accumulation, where traditional lug type tires may provide a traction advantage.
Let’s sum up the strong suits of the traditional rib and lug tires when used on drive axles of a typical tandem drive 18-wheeler:
Systems Influence Design Options
Another factor that’s likely to influence future drive tire designs is the requirement that all new trucks and trailers be equipped with antilock brake systems. These rely on sensors to detect tire rotation by axle or by individual wheel end, depending on system complexity.
With this hardware in place, it becomes possible to add software that can control wheel spin in marginal traction conditions, and, voila you’ve got a traction control system! While it’s not quite this simple, several component suppliers already offer this optional feature which addresses much of the concern about driving traction when using rib tires and other closed shoulder designs on drive axles.
Also, many fleets today are adding comfort and convenience options (and resulting costs) to new trucks in an effort to attract and retain high-quality drivers. Rib-type and new generation hybrid drive tires complement this effort by emphasizing soft, smooth and quiet ride qualities.
Looking Forward at New Materials
Several new tire manufacturers are busy evaluating new materials, designs, and processing techniques to find the optimum combination that will combine many benefits previously available only in rib type tires with the treadwear, durability, fuel economy, and casing longevity required by cost-conscious truck operators.
Drive tires may simply never be the same.®′