Checkbox to the Roadside Inspection Report to Flag Inspections that Require Further Investigation by the Office of Defect Investigation

The Office of Defect Investigation (ODI) recently closed a tire related defect investigation without identifying a safety defect trend. However, the information gathered and knowledge gained from the investigation has convinced ODI that more needs to be done to educate drivers and fleets about the performance limitations of tires and their proper maintenance.

In addition to tire tread depth and age there are 3 interdependent factors that influence a tire’s ability to safely roll down the road: inflation pressure, load, and speed. If any one of these three is changed it has an influence on the others. All tires have a speed rating. This is the maximum speed which the tire can safely be operated when given a specific load and inflation pressure. The majority of commercial truck tires are rated at 75 mph. Some are up to 81 mph. Today’s trucks are more powerful, more fuel efficient and more comfortable allowing drivers to carry heavy loads at higher speeds with fewer stops. This translates into more heat in the tires, which is the number one enemy of tires resulting in failures. Many states have raised their speed limits, yet the speed rating of tires has not increased. Where there used to be a margin of safety, this margin has been reduced, which therefore makes tire maintenance more critical than ever. During the previously mentioned ODI investigation two separate limited surveys were completed. One in PA where the front axle of the tractor was weighted, air pressures taken and compared to the tire load tables. The tire pressure was assumed to be a cold inflation pressure for consistency. 55 percent of these vehicle had an overloaded steer tire. However, only one was out of service based on the current inspection criteria (50% of maximum pressure listed on the sidewall). During this survey the drivers where asked about their tire maintenance. 60% did not know the correct inflation pressure for the vehicle they were driving. Some of the responses included: “I don’t know, the shop takes care of that [air pressure]” “This is my dad’s truck, I just drive it.” “I couldn’t tell ya.” This is a clear indication that drivers are not checking the air pressure routinely. On a separate occasion in VA while inspecting tire placards for non-compliances any truck identified as having a non-compliance was then subjected to a 100% tire inflation check. 16% of these trucks were then placed out of service based on the 50% of maximum tire sidewall inflation pressure. Also during this inspection it was noted, but not documented, that many of the mated dual wheel inflation pressures differed by more than 5 psi. The general expectation is that dual wheels should be within 5 psi in order to equally share the load on the wheel end and not overload one of the tires.

It is requested that CVSA conduct an “Operation Tire Check” similar to Operation Airbrake annually to raise awareness and ensure safe operation of commercial vehicles in regard to tires.