Here is the relevant statement: "when the source of the noises he'd been hearing became evident". So the wheel was cracked and getting worse to the point of making noise (which is really bad by that point) and he just kept driving until it completely failed and fell off the truck. It's got to be making a hell of a racket to hear a right side outer wheel from the driver's seat. Regardless of what caused the CRACK, which could be simple metal fatigue on an older coach like that, or negligence such as over torquing as some have suggested, the cause of the FAILURE is the driver didn't bother to pull over and figure out what was making noise until the tire passed him. And just because the inner valve stem got ripped off in the accident does not mean the inner tire had any air left in it at the time. Realistically, what do you think the odds are of that inner tire having been checked with an air gauge any time in the recent past? As much as the D.O.T. is a pain in my ass, it scares me more that the average untrained grandpa (nothing against us old guys in general) can hop into a piece of equipment just as heavy and complicated as anything I drive with my cdl and tear off down the road with no license, training, pretrip inspection or any sort of accountability. Ok, enough soapbox for one day.