McCoy Truck Tire would like to thank Ryder and Bridgestone for touring our retreading facility in Modesto California on this cool late August morning. In addition to seeing first hand how retreads are made, tour goers received a 1/64th scale Bandag toy truck.
After the plant tour, tire industry experts under Bandag’s employ presented information on best ways to reduce tire running cost in the back room of a nearby pizza parlor. Some of the information available at https://www.bandag.com/en-ca/why-retread was reviewed, as well as an interesting video from the TRIB, https://www.youtube.com/watch?v=GSaZ9EhbCLw .
Although Ryder probably has the lowest running cost/mile for tires in the world, with a slogan like “Ever Better” it’s in their organization’s DNA to continue to review best practices. And that’s where a particularly interesting and detailed presentation made by a seasoned Bandag consultant on the fundamentals of reducing running costs came in. As he illustrated with an example, never ending pursuit of lower cost has re-defined steer tire high-performance; from hoping to make 100k miles before wear out when he started, to going 200k with 7/32nds of tread left on today’s state-of-the-art front-end tires!
As he broke it down, two kinds of factors affect tire running cost; the kind you can control and the kind you can’t. The single most important factor affecting a tire’s useful life is the inflation pressure. Too much pressure can accelerate tread wear. Too little pressure can make a tire behave as if it’s overloaded and generate excess heat which can degrade the casing and lead to detonation (see “Rubber on the Road” video by TRIB).
Central to this science of heat build up’s relation to inflation pressure is the concept of flex-zone. Too little pressure increases the amount of folding that the material in the tire does as it rotates at the 4 to 7 o’clock range.
Another way to improve tire cost is to reduce the speed your equipment is governed at. Think of the maximum speed that a tire can operate at as one of three legs on a three-legged stool. The three legs are ways that heat is generated, and the stool toppling is tire disintegration. The other two legs of the stool are weight that’s being carried and inflation pressure.
The scientists that designed the truck tires put the speed limit at a maximum of 75 mph. This information, by DOT regulation, is molded into the sidewall of most tires on the road in North America, along with a maximum allowed load at a specified inflation pressure. Remarkably, most truck tires are not speed rated for some public roads in Texas!
As load-weight-carried goes down, so does necessary inflation pressure. The veteran of tire consulting referred to an experience he had with an owner of a fleet of gravel-hauling bottom dump trailers. The trailers had abnormally high center of gravity, and irregular wear on the tires had the maintenance budget abnormally high as well. The owner explained; “we run the tires at 110 psi because that’s what carries the most according to the sidewall!”
The consultant did the math and looked at the tire manufacturer’s data-book. He recommended that the owner run the trailer tires at 90 psi. Still rebellious, the owner chose 87 as his air pressure. 45k miles later he called the consultant back out to look at the trailer tires: they had not worn a single 32nd of tread!
How tires are mounted on wheels and how tire-wheel assemblies are mounted on vehicles can also promote slow and even wear. His view was that for truck tires the RPM’s are low enough that balancing tire-wheel assemblies is not cost effective. By the early afternoon the group had branched off into scrap tire and irregular wear analysis.
All in all, it was an inspirational, informative, and refreshing event that was a pleasure to partake.