One tire replacing two tires has many budget benefits for a truck fleet, including improved fuel economy, weight savings and improved brake cooling, not to mention the elimination of dual tire matching concerns and, of course, reduced tire and wheel inventory.
Drivers consistently report that they like the way the tires feel on the road, and today’s super wide tires are not affected like dual tires when it comes to road rutting. Comfortable drivers are happy drivers, and happy drivers make fleets happy.
So it’s little wonder more commercial dealers are recommending super wide radials to their fleet customers.
In general, there are two common super wide sizes: 445/50R22.5 and 455/55R22.5. There are a few others, but these two sizes represent the lion’s share of the market.
The biggest share of the market is clearly the 445/50R22.5 size. One super wide 445/50R22.5 can support a maximum load of 10,200 pounds. The larger 455/55R22.5 has a greater load capacity at 11,000 pounds. In most cases, drive and trailer axles are rated at 17,000 or 20,000 pounds, so specing the 445/50R22.5 still gives plenty of safety.
It has been more than 10 years since the super wide tire market kicked off. The tire is not for every fleet, but sales growth has been exponential. Marketshare numbers vary but they are considered to be in the 5% to 10% range.
Just about every tire company is now offering a full line of super wide drive and trailer designs with varying tread designs, compounds and skid depths. There are also complete lines of retread designs and compounds from which to choose.
Keep in mind that one tire is replacing a set of duals, but the tread width of a super wide tire is not exactly twice that of a conventional radial. A set of dual 11R22.5s have a nominal tread width of 22 inches, while a super wide 445/50R22.5 has a tread width of 17.5 inches.
So what does that mean in the real world? With nearly five fewer inches of tread width, a super wide tire is working harder through every revolution, which places greater emphasis on maintaining proper tire inflation pressure. And if the bigger tire is run 10% to 15% underinflated, it will generate a significantly greater amount of heat versus a set of duals.
Diagnosing Wear Issues
Troubleshooting irregular tire wear issues with super wides is somewhat different than diagnosing conventional tire irregular wear. The Technology & Maintenance Council (TMC) of the American Trucking Associations recently issued a Recommended Practice addressing this very issue of irregular wear specifically on super wide trailer tires. The RP lists all the trailer components, utilization practices, maintenance practices, and super wide tire issues that can contribute to the occurrence of irregular tire wear.
For example, most fleets are under the mistaken impression that antilock braking systems will eliminate brake-related tire flat spotting and localized wear that may lead to irregular wear. In truth, this depends on what type of ABS the fleet has spec’ed.
The premium four-sensor/two-modulator ABS should eliminate flat spotting. The two-sensor/two-modulator ABS will only reduce flat spotting of trailer tires. Also, it is important to make sure that the ABS is working properly. Malfunctioning valves may cause localized tire wear. In addition, the trailer parking brake should be completely released before the trailer moves. This will eliminate flatspots by stopping tire chatter at trailer take off.
Automatic tire inflation systems are commonly used on trailers equipped with super wide tires. It is important to ensure that these systems are set to the fleet recommended inflation specification. The correct tire pressure is based on the worst-case load the tire will see during service. Use the load/inflation tables available online at all the tire company websites to determine the recommended pressure based on the load.
Another potential issue related to super wide trailer tires occurs when running an empty trailer – deadheading. Since the tire pressure was based on the worst-case load scenario, when the load is significantly less when running empty, the tire shoulders are barely touching the ground. This leads to fast shoulder wear. The more a fleet runs empty, the greater the odds of developing fast shoulder wear.
Out-of-balance super wide trailer tires are quite susceptible to irregular wear. Always check that the tire is mounted uniformly and plenty of lubricant was used during tire mounting.
Reducing Irregular Wear
Too much wheel-end play is always a negative when it comes to irregular wear on trailer tires – duals or super wides. Poor bearing conditions will lead to alignment issues; specifically, negative camber and excessive toe that can lead to inside shoulder wear. The same goes for hubs and brake drums. In particular, brake drums should be clean, rust-free and properly seated on drum pilots.
Trailers are not typically checked for alignment compared to tractors. Misalignment is a leading cause of irregular wear on super wide tires, especially in local tanker operations where there are a lot of tight turns. If irregular wear appears on one shoulder, it is usually due to the trailer being out of alignment.
Suspension system maintenance is also important to reducing irregular trailer tire wear on super wides. The use of offset super wide wheels can lead to axle flex. If the super wide trailer tires consistently see heavy loads, the shock absorbers may be working harder. This will require more frequent inspection and replacement in order to avoid irregular wear.
From a tire standpoint, there is a wide range of super wides available on the market. In many cases, a shallower tread depth will create less tread squirm, which is effective in reducing and/or eliminating irregular tire wear. Of course, lower tread depth will also lead to early tire removal. There is always a tradeoff.
But even with some special handling required, truck tire dealers should seriously consider the upside benefits of recommending super wide radials to fleet customers.
