If you know what to look for, scrap-yard tires can tell you a lot about the kind of maintenance and driver care (or neglect) they received. This information can be used to make valuable adjustments in your tire program.
Assuming there has been no significant abuse, neglect or injury, three things can make it necessary to take tires out of service, all of which relate to age. The first is actual age. Many fleets have established guidelines whereby they do not retread tires that are more than 10 years past the original manufacturing date; serviceable tires older than that are restricted to local delivery service.
Tires also “age” as a result of fatigue cycling — the repeated process of carrying load and deflecting through a footprint at the tire/road interface. A 22.5-in. truck tire revolves some 500 times for each mile traveled. In typical service, this mechanism is accelerated on steer axle tires since they operate as single mounts and carry a higher percentage of their rated load than do duals on drive or trailer positions. A third aging mechanism is torque transfer, particularly the constant diesel-engine generated torque run through drive axle tires.
The first order of business in reviewing scrap tires is to separate those that have aged normally from those that have not. The latter should be divided into three groups: (a) those with wear-related conditions; (b) those with structural failures and other conditions that may be warranty related, including both new and retreaded tires; and (c) tires with obvious damage that resulted in premature removal.
When studying wear patterns, it's important to distinguish among those caused by: (a) equipment, either design or maintenance related; (b) vocational operating conditions, often a result of not matching the tire to the application; and (c) conditions that are common to a particular brand or design. (Most wear-related conditions can be found in The Technology & Maintenance Council's (TMC) “Radial Tire Conditions Analysis Guide,” available from ATA at 800-282-5463.) Once a diagnosis is made, you can focus on prevention for the future.
When analyzing structural failures, consider new and retreaded tires separately, since they're probably at different stages of their normal life expectancy. When you choose a retread supplier, make sure to determine who will take responsibility for non-maintenance related tire failures. And when you're selecting new tires, look at factors such as changes in equipment configuration, including suspensions, wheelbase, single vs. tandem drive and tire size.
Premature removal due to damage or injury should be identified and corrected promptly, since many tires in this category tend to have otherwise serviceable tread and casing life remaining. Occasionally, some tire conditions simply indicate the need for selective driver education. Sidewall ruptures from curbing and brake skids fall into this category, although the latter can also result from brake problems or equipment mismatching.
Repairs should also be examined, not only for integrity and failure frequency, but for frequency of occurrence. For example, many fleets have reduced tire costs by using magnets on yard switching tractors in an effort to gather errant nails, etc., before they cause tire punctures. It can also be useful to relate tire failures to specific truck or trailer units if those vehicles are dedicated to individual customers and/or drivers. Comparisons to overall failure rates often reveal differences that can either be controlled or factored into future cost allocations.