As I was driving home from work one day, I couldn't help but notice the increasingly obvious number of trailers and tractors that were parked at various businesses along the Interstate. One major trailer dealer had used equipment two and three deep in his back lot, which appeared to be full. With so many tractors and trailers just sitting idle, my only thoughts were of the tires that are slowly “drying out” with each passing month.
While it's just my opinion, I'm fairly confident that thousands of truck tires and casings are unnecessarily scrapped on an annual basis because the sidewall rubber starts to develop small cracks. The weather-checking or “dry-rot,” as it's known, poses no risk to the performance of the casing in its minor stages. In fact, in order for it to result in any damage, it must extend to the steel body cables or be greater than 2/32 of an inch deep. Of course, not all sidewall cracks should be ignored. Large circumferential cracks about an inch above the rim flange and small cracks near the shoulder should be inspected by a tire professional. But just like the theory that all roadside tire debris is the result of faulty retreads, the court of public opinion has already determined that all tires with sidewall cracks should be immediately removed from service.
Tire manufacturers have made incredible advances in developing rubber compounds that are resistant to the effects of ozone and ultraviolet (UV) rays, but most will still develop some cosmetic cracking as they age even when perfectly maintained and stored indoors. While age plays a role, it's not the only factor. I've seen six-year-old casings with very minor weather-checking and three-year-old original tread tires with cracks so numerous and deep I was amazed that the tire was still inflated.
While it's human nature to be skeptical of the casing's integrity, it bears repeating that the cracks typically need to be 2/32 of an inch deep in order for there to be any concern. Unfortunately, the law enforcement community will instinctively be drawn to tires with severe weather-checking, so fleets and operators are forced to take steps to prevent them from being left in service. Since it's inevitable, the first key to preventing this from turning into a blinking red light that screams “inspect me” is to make sure the tires get regular exercise.
As I mentioned previously, chemicals are added to rubber compounds to combat the effects of ozone and UV light. In order for those additives to minimize or prevent weather-checking, however, the tires must be periodically operated so the rubber flexes and remains pliable. The longer the tires sit, the more susceptible they become to weather-checking, so fleets need to find ways to rotate idle equipment into service. And companies that purchase used tractors or trailers should also carefully inspect the tires because in some cases they may need to be replaced.
Another factor that contributes to weather-checking is the excessive use of protective sidewall “dressings” and caustic tire cleaners. Most of these products actually contribute to the problem by drawing the chemicals to the surface and away from the rubber. It's also important to note that prolonged underinflation and heat damage can increase the rate and severity of the cracking so basic maintenance is vital. Since weather-checking is unavoidable, fleets and drivers should not be alarmed when small cosmetic cracks start appearing on the sidewall. If there is any doubt, contact the tire manufacturer or a tire professional for their assessment before scrapping the tire.