Where the Rubber Meets the Road – Why Tires Fail

By June 3, 2015 June 16th, 2015 Maintenance, Tires

It’s not too much speed that may cause tire failure; it’s likely too little inflation.

Those in the commercial trucking industry are all too aware that tires are huge cost centers for fleets; in fact, they’re among the top three or four cost centers, according to a May truckinginfo.com article. So keeping those tires in good condition is vital to a fleet’s positive balance sheet. So why do tires fail or wear out too soon? Since last week was National Tire Safety Week, this seems like a good topic to discuss and to clarify.

In early April, truckinginfo.com ran a story, “Too Fast for Your Tires?” that dealt with the perception on the part of the press, and often the public, that driving too fast is a major reason why tires fail. I would recommend reading the article, which goes into great detail on one of the actual reasons why tires may fail. In many cases, it has more to do with maintenance than speed. As the article notes, almost all North American on-highway truck tires are rated for 75 mph, and most trucks are probably not going to exceed that speed. But when it comes to maintenance, specifically proper tire inflation, the numbers are not good. According to the article’s author, Jim Park, Equipment Editor for Heavy Duty Trucking, a TMC study found that only 44% of tires were within +/- 5 psi of target pressure. Park also notes that an earlier article he wrote concerning inflation pressure in steer tires received a large volume of comments; and those comments clearly indicated that readers (and quite possibly, drivers) were not aware that a maximum load would require elevated pressure in the tire. When many of us hear statistics like 40% of tires are underinflated, we correlate that to the targeted pressures set by the fleet manager.  The big concern is the weight each tire will carry and setting the pressure for that tire to the manufacturer’s recommendation. This can be significantly different than the fleets standard tire pressures. As fleet managers we like to standardize as much as possible, however we need to be cognizant of each tires application, load, and speed to ensure it is within the recommended limits. If not the consequences can be alarming.

There’s another component that needs to be considered when replacing tires – especially steer tires. Does the tire rating meet the minimum required axle rating? An example is a vehicle with a 12,000 lb. front axle using G-rated LP22.5 tires which could have a 6,100 lb. single load capacity. Put that same tire on a 13,200 front axle and the tire is overloaded. An (H rated) tire or even a larger tire size may be needed to meet the axle capacity. Again, we like to standardize tire inventory whenever possible but be sure the tire weight rating and the tire pressure meet the load and capacity for the application.  It is important to make sure the technicians installing replacement tires confirm the tires being installed meet the axle rating.

Regardless of whether it’s a matter of over- or under-inflation, or ply rating, make sure your maintenance team is performing regular maintenance on all of your fleet’s tires.

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Joe Puff

About Joe Puff

Joe Puff is the Vice President of Truck Technology and Maintenance for NationaLease. He has more than 35 years of experience in complex sales and fleet operations, including extensive experience in commercial vehicle maintenance. Joe is responsible for advising NationaLease members and the National Account team of new truck technology, industry trends, and maintenance best practices.

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