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Tire size and type selection for Class 6-8 highway trucks is almost a science for most fleet users and their dealers.

Recent developments, such as super wide single tire options and selected self-sealing highway tires, may warrant a fresh look, but the choices are relatively simple and well known among dealers. This is certainly not the case for many light- and medium-duty fleet vehicle buyers.

Many trucks and truck chassis with GVWR ratings under 14,500 lbs. are designed primarily for personal use service, or, at best, a combination of personal and commercial use.

Recently, the trend has been an increase in weight for these vehicle types, as diesel engines (heavier than gasoline fueled counterparts) have increased in popularity. Also, the engines on these trucks generally require heavier, upgraded powertrain components. Additionally, recreational trailers (pull-behind and fifth wheel-types) have become more plush and, consequently, heavier requiring heavier towing vehicle ratings. Along with these trends, there has been a significant emphasis on improved vehicle ride, handling and noise reduction. From a tire viewpoint, these tend to be opposing design parameters.

I recently had the opportunity to drive a new diesel powered pickup towing a fifth-wheel RV trailer from Michigan to Florida. It had a GVWR of 14,500 lbs. and the trailer alone scales a bit over 23,000 lbs. While the ride and noise levels were what one might expect in a luxury sedan, it concerned me that no CDL or training beyond a regular driver’s license is required to pilot this articulated rig. Also, it was obvious that the tires had been carefully selected and tuned for comfort rather than cost-per-mile commercial productivity.

There are many light- and medium-duty commercial truck applications, ranging from utility service to package delivery, with endless variations in between. Users are downsizing vehicles for a variety of reasons, and this can result in the selection of up-spec’d smaller trucks vs. the down-spec’d big trucks of yesterday. In many cases, this may be satisfactory, but some caution is in order, especially in the areas of vehicle handling, tire selection and tire program costs.

Commercial tires are designed for long original treadlife, extended casing durability and multiple retreads. They generally operate at higher inflation pressures that add load carrying capacity and lateral stiffness. These qualities are especially important, for example, on bucket trucks, raised roof vans, small dump trucks and others that have relatively high centers of gravity and/or heavier loads.

Aggressive, deep-tread traction tires designed for the personal use 4WD market should generally be avoided, or at least carefully evaluated before being selected for these vehicles. On the other hand, heavy-duty radials with steel casing plies tend to be less vulnerable to sidewall damage and, ultimately, early removal and scrapping. The extra cost of steel ply/steel belt tires for commercial use usually can be justified by the residual casing value and retreadability.

Other features to be avoided for most commercial service applications are unnecessarily large rim diameters and wide tread tires. Optional larger tire/wheel combinations on light-duty trucks are mostly intended to enhance styling and image. They nearly always come at a cost premium that won’t be recovered in extra performance. Wider than necessary treads can create vulnerability to irregular wear, since the outer tread edges are displaced more for any alignment inaccuracies, especially toe and camber settings.

They are also more likely to wear faster in service that includes high frequency and severity of wheel cut – normal operating conditions for many of these vehicles. Wider than necessary treads are not appropriate for winter driving and snowplowing service, where the increased unit tread pressure of narrower tires provides far superior traction.

Good advice from knowledgeable tire engineers or field service reps is invaluable for avoiding tire/wheel issues when helping your fleet customers spec light- and medium-duty trucks for commercial service. Fortunately, much information is available, but you need to ask.

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Asa Sharp

Asa Sharp

Asa Sharp

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