Judgment calls have been part of the tire industry since I was a teenager working out of a road service truck. Imagine driving 20 mi. into the middle of nowhere to fix what you think is a flat tire only to find out that the inside of the tire is a tangled mess of steel and rubber; that tire was flat long before the driver noticed. And since you just came from another jobsite, you don’t have a replacement, so you’re left with two options: drive back to the shop to pick up a tire or single it out.
From the standpoint of the service provider, the choice will always be to drive back to the shop and pick up a new tire. Attempting to repair a tire on the side of the road is complicated enough to begin with when the bolt is in the middle of the tread and well within industry guidelines. If even a hint of run-flat is present, the technician has to make a very difficult call on the spot. There are so many things that can go wrong and with the consequences so severe, most truck tire dealers prefer to just replace the tire rather than attempt a repair.
But what happens when the driver and/or company refuse to replace the tire. It’s still a fairly common practice to demount the scrap tire and allow the vehicle to proceed with a missing tire on one dual. In fact, the general rule used to be that it was acceptable if the truck or trailer was empty because the unloaded weight would not overload a single tire in a twin screw or dual-axle trailer configuration. Fleets have been taking advantage of this practice for decades in order to save money on costly road repairs.
In another prime example of wishing the question was never asked, it looks like the practice of singling out is in violation of Federal Motor Vehicle Safety Standard (FMVSS) 571.120. This little-known regulation basically states that the sum of the maximum load ratings of the tires on an axle cannot be less than the gross axle weight rating (GAWR) established by the manufacturer. A 20,000-lb. axle must have tires that can support 20,000 lbs. Unfortunately, the standard 295/75R22.5 comes up 2,975 lbs. short when one of them is missing.
Therefore, what used to be a judgment call is now clearly defined. It is a violation of FMVSS 571.120 to single out a tractor or trailer regardless of the circumstances. If the trailer is empty and 50 mi. from the terminal, the options are to have someone drive out with a spare or buy a tire. Trucking companies can expect more dealers to be less likely to single out any type of vehicle because they don’t want to be part of a possible lawsuit. I’ve personally had drivers swear on the lives of their children that they would get the tire replaced only to watch them come back a week later with the same bald or missing tire.
Safety regulations are in place to protect the motoring public, so it’s easy to see why the sum of the tires cannot be less than the established GAWR. There’s no guarantee that the empty trailer with seven out of eight tires will stay empty until there is a full eight tires carrying the load. When it comes to regulations like FMVSS 571.120, the industry doesn’t have to like them, but we still have to follow them.
I hope everyone enjoyed the free ride while it lasted because singling out truck tires is no longer an option when a tire needs to be replaced.