Failure analysis always has been about sleuthing-looking at a component, finding evidence of what led to its demise, and then prescribing steps to help customers avoid a recurrence.
But while some components are easier to read than others, tire analysis can swing to either extreme. The following are examples from the Technology & Maintenance Council’s (TMC’s) Radial Tire Conditions Analysis Guide.
Tireside Reading
Tires usually are easy to read when they wear their scars on the outside. Misalignment, imbalance, improper inflation and driver abuse all leave telltale tread wear or obvious sidewall damage. Except for prolonged underinflation and severe sidewall damage, these more obvious conditions usually can be remedied and the tire then can be returned to service.
For example, the tire in Figure 1 displays rib feathering, where ribs are more worn on one side than the other. The cause is excessive side force, almost always the result of misalignment-usually excessive toe-in or out or – damaged steering or chassis components.
On the other hand, scalloping or cupped tread around the entire circumference of the tire, usually at the shoulders (see Figure 2) results from a tire/wheel out-of-balance condition, improper mounting or other assembly non-uniformity. And, since any tire/wheel assembly has some amount of imbalance that often is held in check by shock absorbers, a bad shock can be the culprit.
When there’s significant imbalance, one part of the assembly is substantially heavier than the rest, causing that part of the tire’s tread to strike the pavement with additional force. This chews away rubber until that part is no longer the heaviest.
Then, a new heavy spot often develops, and the scalloping migrates around the entire circumference. Once the imbalance is fixed, the tire often can be returned to service on a drive axle, according to TMC, where the tread irregularities will be evened out.
