Scrap Yard Gumshoe
Regardless of the type of spent machinery, component equipment, or materials they
provide a gathering place for, scrap yards contain an abundance of information. Witness the differences in average mileage accumulated or failure modes for various models of automobiles prior to reaching their final rusting place. Or the average age difference between scrapped cars in rust-belt states and those in dry southwestern climates.
It’s also reasonably easy to get a good overall picture of the degree of maintenance and driver care (or neglect) based on several simple observations. Scrap tires, especially those from trucks and other commercial applications, are no different and can yield valuable information to astute observers. This information can often be parlayed by dealers into tire program cost reductions for their customers.
The first step in becoming proficient at extracting information from scrapped tires is to develop a good understanding of why tires should "normally" be scrapped. Tires, like all manufactured composites, do have a finite useful life expectancy, which can be cut short by the usual problems of neglect, abuse or injury.
Tire engineers and rubber chemists say there are three other conditions that commonly account for the early termination of a tire’s service. First is pure age. Radial truck tires are assembled chemical composites, typically containing approximately 40 separate pieces and 10 or more different rubber compounds. These components simply wear out and their physical properties degrade over time.
Many fleets have established guidelines of not retreading tires older than 10 years from the date of original manufacture and restricting serviceable tires older than that to local delivery service.
Secondly, tires grow old by fatigue cycling, the repeated process of carrying loads and deflecting at both the footprint and sidewall areas. A 22.5-inch truck tire revolves approximately 500 times for each mile traveled. At highway speeds, that tire is deflecting to various degrees based on load ®“ 30,000 times each hour. In typical service, this is accelerated on steer axle tires since they operate as single mounts and carry a higher percentage of their rated load compared to duals on drive or trailer axle positions. Steer axle tires also have to withstand the lateral deflection that accompanies turning.
A third aging mechanism is torque transfer, where the tire sidewall is literally circumferentially stretched momentarily as engine or brake power is transferred to the tire. Both acceleration and braking torques could be considered, but the constant diesel engine-generated torque run through drive axle tires is a dominant factor in aging those tire casings.
Finding the Cause
Since the above mentioned mechanisms are as inevitable as taxes, the first order of business in reviewing scrap tires is to separate those that have aged normally from tires that exhibit different conditions conditions that may be more controllable.
The second step here should be to divide these tires showing potentially controllable conditions into three groups: those having wear-related conditions; those with structural failures (separations or other warranty-related problems, including both new and retreaded tires); and tires that have obvious damage or injuries that caused premature removal from service.
Nearly all common tread wear-related conditions are described and illustrated in The Technology & Maintenance Council’s (TMC) publication "Radial Tire Conditions Analysis Guide," available from ATA at 800-282-5463. This publication is an excellent working reference and training guide.
The TMC guide suggests probable causes for many different tire conditions, and includes illustrations of most of these. Fellow dealers, fleet maintenance personnel and tire field engineers can also be helpful consultants. Several opinions are sometimes required in order to home in on the particular cause of premature wear-related retirement.
When studying tread wear patterns, it is important to distinguish among those caused by equipment (design or maintenance-related), vocational operating conditions (often a result of poor matching of tire design to the job conditions), and conditions that are common to a particular tire brand or design.
Once this diagnosis has been made accurately, the issue of what needs to be changed for improvement becomes more focused.
Analyze What Went Wrong
Analysis of tire structural failures can also be assisted by information in the TMC publication. It’s a good idea to consider new and retreaded tires separately, since the tires are likely to be in different stages of their "normal" life expectancy. Also, responsibility for any pure product-related shortcomings may fall to different suppliers, adding another variant to your investigation. An important part of selecting a retread supplier should be an agreement on responsibility for non-maintenance-related failures of retreaded tires, including the casing.
Another consideration should be reviewing past experiences with the subject tires in that particular application. Some apparent structural deficiencies may simply result from the tire type and operating service conditions being incompatible. Changes in equipment configuration, such as suspensions, wheelbase, single vs. tandem drive, or tire sizes may also be a contributing factor, and should cause you to review new tire selections.
It’s always a good idea to consult tire manufacturer reps when specifying OE tires on new power units and trailers, as many specialized tire models have been developed to address variations in equipment and vocation.
Identify Damaging Situations
Premature service removal due to damage or injury should be identified and corrected promptly, since many tires in this category tend to have tread and casing life remaining. According to recent International Tire & Rubber Association scrap tire studies, too many otherwise useful truck casings with repairable injuries are heading to the landfill instead of to a retreader.
It is not uncommon for a fleet to lose from 15% to 25% of its new tires to damage or injury prior to them reaching the first retread. Tire damage/injury could be caused by road hazards, poor inflation maintenance, and even careless driving.
Occasionally, your scrap investigations will reveal some tire conditions that simply indicate a need for better driver education/training. Sidewall ruptures from curbing and brake skids fall in this category, although the latter can also result from brake system problems or equipment mismatching.
Repairs should also be examined, not only for their integrity, but frequency of occurrence. For example, many fleets have reduced tire costs by using magnets on yard switching tractors to gather errant screws, bolts, nails and other objects before they can puncture a tire.
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.
Comparing these separate and unique situations to a fleet’s overall failure rates often reveal differences that can either be controlled or factored into future cost allocations.
How much information can be gained by scrap yard inspections depends both on how carefully you look and how well you interpret what you are seeing. Experience and an understanding of the complex working relationships among equipment types, maintenance, drivers, tire suppliers and retreaders, are extremely important in successful scrap tire analysis.
Some fleet managers and tire industry field personnel are knowledgeable veterans and are willing to help if you just ask. Your customers will appreciate your expertise and trained eagle eye-approach to extending their tire budgets. At the same time, your reputation will help bring additional business opportunities.