A heap of scrapped tires is a wasteful thing, and not simply because of the space it consumes. Disposal costs aside, the pile can represent a significant share of wasted maintenance dollars.
An estimated one in 10 disposed tires could be put back into service with a proper repair, while about three in 10 boast casings that could support retreading, says Harvey Brodsky of the Tire Retread and Repair Information Bureau.
“This is the weak link in the tire industry.”
No kidding. The drive tire on a linehaul truck can typically support two retreads, with a third retread transforming it into a useful trailer tire. The tires used by a refuse hauler may be candidates for up to 10 retreads because multiple starts and stops will scrub away the gripping pattern of rubber long before the end of the casing’s useful life.
Are your tires subjected to a shorter life than that? A quick review of your tire program could help maximize your investments in the valuable rubber that meets the road.
Even though warranties on new casings are generally limited to five years, an older tire may still be a candidate for retreading. It comes down to the effectiveness of maintenance procedures, and that requires a close eye on factors such as tread depths.
While the tread on a linehaul truck’s steer axle tire can legally run down to 4/32nds of an inch, and drive tires can legally run down to half of that, tires should be pulled off for retreading when treads wear down to 6/32nds of an inch. (Mixed fleets may want to pull tires off their trucks at 8/32nds because of the likelihood that treads have been exposed to additional damage.)
“If you’re going to retread, don’t try to squeeze every bit of juice out of the lemon,” Brodsky says. The shallower rubber offers little protection to the valued casing underneath. A drive tire that would otherwise deflect the debris fired off a steer tire could suddenly face a puncture.
That isn’t the only step to extend the life of the casing. A tire program should ensure proper alignments, balancing, and the use of calibrated tire gauges to maintain optimal inflation pressures. If the pressures run too low, a tire will flex more than it should, and the cords inside will generate heat and break. (If you want to understand how that can lead to heat, simply bend a paperclip back and forth until it breaks, and hold the broken end up to your cheek.) Over-inflated tires can cause their own problems for those who haul light loads.
The best-possible inflation levels should be determined by the charts in a tire data book, Brodsky adds, noting how tire dealers are more than eager to teach fleets how to read the seemingly cryptic information. The pressures should also be measured when tires are cold.
New technology for inspections may even help to produce retreaded tires that are more reliable than their brand-new counterparts.
It seems like an empty boast until you track the number of manufacturer defects. A typical major tire manufacturer will report an “adjustment rate” of 1.0% to 1.5%, Brodsky says. A little over a decade ago, retreaders were recording adjustment rates of two to three times that rate.
That was before modern inspection equipment became commonplace. Rather than relying on bright lights and the sharp eyes of trained inspectors, a modern retreading operation can examine casings with techniques that capture images of tires that are stretched within the confines of a vacuum chamber. Electric impulses can locate holes and cuts that would otherwise be invisible to the naked eye.
An inspector of the past didn’t have X-ray vision, Brodsky says.
“We turned him into Superman.”
Perhaps a Man of Steel Belts.
Unlike its brand-new counterpart, the casing on a retread has also proven that it can hold air and remain in service for tens of thousands of kilometers of active service.
When it comes time for retreading, the old rubber will be rubbed off using an accurate buffing mechanism, and the new tread will be applied using one of two techniques, each of which will produce a reliable product.
In the pre-cure system, a thin layer of cushion gum is used to stick a pre-cured tread onto a buffed tread area. The tire is then loaded into a curing chamber, where the pre-cured tread is attached to the tire in a vulcanizing process that is pretty similar to the one used to attach treads onto a new tire.
In a mold cure system, the unvulcanized tread is attached to a buffed tire, and put in a mold that features the desired tread design. The tread itself is created when the mold is heated. Like the pre-cure system, the vulcanizing is similar to the process used in the production of new tires.
In either case, the final product needs to be retreaded, excess rubber is trimmed off, and the final product is painted.
When all the enhanced procedures are considered, the rate of defects among retreaded tires has dropped below 1%, Brodsky says.
As good as new. Maybe better.
Of course, some tires fail long before it is time for a retread. You can thank the endless supply of debris on roads and fleet yards for the punctures and tears that emerge. But dig a little deeper into the scrap pile, and you may also unearth tires that failed because they were not properly repaired.
Golf-tee-shaped plugs can be used to patch punctures that are up to 3/8 inches in diameter but they need to be inserted from the inside of the tire to be effective. The inside of the tire also needs to be properly cleaned and buffed with a grinder that runs at a slow speed to avoid curing the rubber. The hole itself will need to be filled with a vulcanizing material to protect the belt package from separating, and to prevent moisture and other contaminants from entering the casing.
Damage that is more extensive can be addressed with radial section units. The International Tire and Rubber Association – a predecessor to the Tire Industry Association – has even determined that it is possible to repair sidewall damage measuring as much as four-by-3/4 inches. Just keep in mind that such repairs involve more than the bead-to-bead retreads often referred to as remoulding or remanufacturing, since the additional treatment on the sidewall is strictly cosmetic.
To avoid unwarranted out-of-service defects relating to the repair, however, it may also be important to educate drivers about the meaning of blue triangles molded next to section repairs, indicating that the bulge measuring up to 3/8 inches high is perfectly legal. The markings may need to be pointed out to roadside inspectors.
Ultimately, each $30 repair could reclaim a $400 investment that was scrapped before its time.
Whether the work involves a repair or a retread, the supplier behind the retreads and repairs will determine a tire program’s success or failure.
How do you determine who should do such work? The Tire Retread and Repair Information Bureau notes that fleets should visit any retreading plant they intend to use. You may not be an expert in the retreading process, but you can still judge the cleanliness of the shop floor. Any debris floating through the air can compromise the glue that will be used to attach the retread. References should also be checked, and shops should be asked to provide their adjustment rate. An unusually high percentage of defects can be expected from those that don’t have the equipment to properly inspect casings.
Regardless, every tire program should focus on the overall lifecycle cost of a tire, Brodsky says.
The latest trailer full of may-pop tires may seem like a good investment, until you factor in the cost of downtime, service calls, and the inability to add a retread.
Students may refer to the three Rs as reading, writing and arithmetic, but savvy fleets will understand that the three Rs actually refer to reviewing, repairing and retreading.
It is a lesson that will pay valuable dividends.
* Protect valve stems with metal caps that contain a rubber gasket if you want to ensure a truly airtight seal.
* Match any duals so that there is not more than 1/4 inch difference in diameters and 3/4 inch difference in circumference. Otherwise, you can expect flat spots to develop on the smaller tire that is dragged along for the ride, or loading related damage on its larger counterpart.
* Teach drivers and mechanics to run their hand over treads to identify flat spots, bulges, irregular wear, or missing chunks of tread. That may spot a potential problem before any trips begin.
Source: Tire Retread and Repair Information Bureau
John G. Smith is a technical correspondent who provides coverage of equipment-related issues. As former editor of Truck News and Truck West, he shows a passion and deep understanding of industry issues.