Trailers Should Sometimes Come First

If the headline above caught your attention and conjured up visions of big rigs heading down the highway backward, we accomplished half of our mission. Make no mistake, we’re not advocating changing the direction of traffic flow, but we do want to underscore and explore the importance of devoting some serious thought and analysis to the selection and maintenance of over-the-road trailer tires.
There are some basic operating cost considerations, as well as some industry trends, that support a new focus on trailer axle positions.

Where Shallow Really Works

Resistance to irregular and premature wear, while obtaining the highest overall tread life (removal mileage) potential, is the primary consideration for most operators. This necessitates a tire choice that is primarily dependent on service conditions, especially frequency and severity of trailer axle side scrub.
Long distance high speed rigs with minimum local delivery work will benefit from the current generation of premium casing, shallow tread trailer axle-specific tires. Compared to deeper tread options, these tires offer improved fuel economy as rolling resistance improves as the tread wears.
As everyone knows, tire contribution to total truck fuel economy increases for free rolling tires at steady speeds.
With the absence of high lateral forces in the tread footprint area, shallow tread tires also tend to reduce irregular wear. Many operators also report better results, including lower operating costs, with shallow tread tires on trailers equipped with air ride suspensions.
One large manufacturer of dry vans and refrigerated trailers reports that the percentage of new trailers produced with air ride suspensions is currently near 70% and rising, compared to 15% only five short years ago.
This trend is being driven, in part, by the rapid increase of electronic goods shipments and the development of lower tare weight, reduced maintenance air suspension designs.

Going Deeper Depends on Case

Local delivery service, including tight maneuvering in congested areas, favors selection of deeper tread tires, such as those used on steer positions of line haul or metro service power units. Food service trailers and metropolitan area petroleum delivery tankers are good examples of these applications. Many of these high-scrub service conditions simply create fast wear rates and unacceptably low removal mileages of the more fuel-efficient shallow tread tires.
Irregular wear is seldom a problem, as the fast wear rate tends to obscure or eliminate this condition. One caution here is to avoid deeper tread tires with de-coupled or undercut shoulder ribs. These are designed to reduce irregular wear on line haul steer axles, but may be susceptible to shoulder rib tear in high scrub trailer service, especially on tandem axle units and on trailers subjected to frequent curbing.
   Many users also find that 70-series or lower aspect ratio tires are more susceptible to sidewall and shoulder damage in high scrub service, especially on tandem axle trailers, as tires on these units are forced to slide laterally in tight turns.

Spread Axles Add Scuff

   Special consideration must also be given to tire selection for spread axle trailers. These are generally defined as having more than 60 inches between adjacent axles, and include all trailers with three or more fully utilized axles. These configurations can create very high degrees of tire side scuff when turning and generally require deeper tread tires with solid shoulder ribs to achieve satisfactory tread life. Some tire manufacturers even produce specialized low tread radius (more rounded shoulder) tires for these applications.

Dead Heading Kills Tires

One other service factor relevant to tire selection is trailer loading. Most users report tires deliver optimum tread life when operated under consistently loaded conditions. Irregular wear tends to develop during lightly loaded or empty runs. The selection guidelines above should apply to operations in which the trailer is usually loaded, including most diminishing load delivery uses.
However, if dead heading makes up a high percentage of total trailer mileage, irregular wear should be monitored closely. Selection of shallow treads – even in some local operations ®“ tire rotation, inflation adjustments, and increased use of retreads may be required to contain costs.
With the increasing popularity of air ride suspensions, some operators are now considering suspension systems that allow lifting one or more axles of multi-axle units on empty-load return runs. Consultation with experienced tire company representatives is especially useful here.
Maintenance of trailer tires should also be reviewed periodically and prioritized. Many cost-conscious operators have recognized their high investment in premium radial trailer tires and concluded that additional maintenance is justified.

Retreads for High Torque Units

It’s becoming widely recognized that transfer of driving torque is one service condition that tends to age tire casings over time. The trend in over-the-road diesel power units favors higher torque ratings. Therefore, it makes sense for many operators to retread used drive tires for use on free-rolling trailer positions, and retread high quality trailer tire casings for drive tire service.

Avoiding Roadside Problems

In addition to extending removal mileages, emphasis on reliability has also increased. One large tire manufacturer reports the average road service call requires approximately two hours of roadside downtime and costs from $400 to $600. It is also common to end up with a new tire that doesn’t match the brand or tread type of others on the rig. Barry Petrea, Goodyear’s commercial tire marketing manager, indicates that 70% of their requests for emergency road service are for trailer tires.
Aside from this out-of-pocket expense and the risk of delaying customer deliveries, roadside safety is an increasing concern. More frequent inflation checks and visual inspection of trailer tires could also contribute to a reduction of failed tire pieces along the roadside – one of the industry’s major image concerns.
With the development of axle-specific tread designs for both new and retread tires, and the use of premium casing types on axle positions, it’s more important than ever that operators consider a comprehensive tire program for all wheel positions. Planning tire selection and maintenance separately for power units and trailers can result in higher operating costs, and that brings us to a bottom line problem fleets don’t want to face.