Failure Analysis
Mark Putz
Associate Editor
When it comes to figuring out why a tire failed, you should avoid pinning the destruction on the usual suspects. For example, a tire comes into the shop with scalloped or cupped tread around both shoulders. This damage is usually the result of out-of-balance wheels. But before you finger this common offender, you must rule out improper mounting or axle assembly.
It's not rocket science, but to be a good tire-failure detective you should stay up-to-date and take advantage of all available resources. The Technology Maintenance Council's Radial Tire Condition Analysis Guide is the latest aid for tire detectives bent on nailing the myriad culprits that lead to wasted tires.
The third and latest edition of this trucking industry mainstay includes new failure conditions to help tire maintenance staff identify radial tire problems. As part of the update, the four-color guide features revised photography to clarify the different conditions. At 200-plus pages, or on a CD ROM, the guide contains detailed, expert descriptions of every tire failure and service condition - both original and retreads. It is available in English and Spanish versions.
The Eye Finds The Familiar
Visible clues on a tire's exterior are familiar and often remedied by a mechanical correction and a position switch. Misalignment, imbalance, improper inflation and driver abuse will all leave this type of obvious evidence. Except for prolonged underinflation and severe sidewall damage, tires exhibiting these scars can usually offer further service. However, tires with internal damage are much harder to read.
According to TMC's guide, such damage could be the result of an improper repair. Examples in the guide include instances where the nail-hole patch was too small or where a repair allowed moisture to contribute to belt corrosion and weakening. And speaking of belt failure, it's important to note that the "zipper" type sidewall failure is not only the result of tire pressure neglect, but can result from any injury or condition that fatigues the casing cords.
Scrap Or More Service?
Can your failure analysis be overly cautious? Sometimes. For example, some old-timers believe a torn bead (perhaps caused by a forklift or by poor mounting/dis-mounting procedures) means a scrap tire. Not so, say industry experts. If there's no rust or damage to the wire, the bead can be repaired and the tire returned to service. However, a tire with a brittle bead from overheating should be yanked. According to TMC, this sort of bead damage often results from heat transferring to the tire through the wheel, perhaps from hard braking. If this condition becomes prevalent in your fleet, it's likely the brakes lack sufficient air flow, are improperly adjusted, defective or dragging. In fact, remember that your spec'ing decisions regarding wheels must be factored into your tire failure analysis.
For more information on wheels, see TMC's User's Guide to Wheels & Rims, which offers best maintenance practices for medium and heavy duty wheels and rims in accordance with DOT regulations. Developed by the industry's foremost wheel and rim experts and maintenance personnel, this guide will help shop personnel analyze wheel and rim problems.
Regardless of the resource, smart fleet managers know printed tools are an indispensable education tool. Whether it's a guide book from TMC or an informal, in-house document, treasure these inexpensive cost-saving tools.
