Will they soon have the advantages of both lug- and rib-type tires? Automobile tires have changed so much that many engineers agree it's difficult, if not impossible, for motorists to predict winter tire-traction performance based on the look of the tread.
New rubber compounds that enable treads to remain compliant in cold temperatures, and CAD-generated tread designs that optimize tread pressure distribution and tread-element phasing without excessive noise and vibration have truly advanced the state of the art. Not to mention the fact that roads have improved, especially limited-access highways.
Is it possible that the time is right for the evolution of lug-type drive tires for trucks as well?
Some tire manufacturers already offer hybrid designs that feature closed shoulders, yet retain discontinuous center ribs and deep tread depths. Some hybrids are designed to address the compatibility issue that arose with the introduction of air-ride suspensions on tandem-drive highway tractors. The softer ride of the air suspensions can lead to uneven wear and premature tire removal on vehicles spec'd with more traditional lug designs.
Before the hybrid designs were available, some fleets experimented with steer-axle-style rib tires on drive wheel positions. They reported significant improvements in fuel economy and ride. More specifically, less high-frequency vibration was especially noticeable in sleeper compartments. There were also reports of more responsive handling, although this hasn't been a big issue for large over-the-road trucks. The biggest downside reported by fleets using rib tires on drive axles was a shortfall in removal mileage, especially in high-torque applications such as heavily loaded single-drive-axle rigs.
As far as traction is concerned, rib tires generally deliver good driving, braking and lateral traction on wet and dry paved surfaces. But traditional lug-type tires may have a traction advantage on soft or deformable surfaces such as mud or heavy snowfall.
Let's summarize the advantages of traditional rib vs. lug tires when used on drive axles of typical tandem-drive 18-wheelers. Traditional rib tires are superior in terms of fuel economy; wet traction; soft, smooth ride; heel/toe or alternate lug wear; and wheel rotation flexibility. Traditional lug tires have the upper hand when it comes to treadwear/high removal mileage and traction in mud and snow.
Another factor that's likely to influence the design of new drive tires is the requirement that all new trucks and trailers must now be equipped with antilock braking systems (ABS). ABS works by using sensors to detect tire rotation by axle or by individual wheel end, depending on the complexity of the system. With this hardware in place, software can be added to control wheel spin in marginal traction conditions.
It's really not quite that simple. But several suppliers already offer this optional feature of traction control, which addresses much of the concern about traction when using rib tires and other closed-shoulder designs on drive axles.
Many fleets today are also adding comfort and convenience options 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, quiet rides.
Finally, several tire manufacturers are busy evaluating new materials, designs and processes, with an eye toward that optimum combination: a drive tire with the classic benefits of the rib design, as well as the treadwear, durability, fuel economy and casing longevity demanded by fleets. Drive tires may never be the same.
