The left front tire separated from a tractor trailer, crossed a grassy median and collided with an oncoming vehicle resulting in a fatality accident. Witnesses reported that the tire was on fire and numerous spot fires were created along the tire path through the grassy median. The tractor trailer's front wheel bearings had been replaced within the past 25,000 miles.
Following the highway patrol accident investigation, the tractor trailer's front axle and steering assembly were retained, but were not properly preserved (see evidence preservation). Metallurgical failure analysis revealed that the tractor trailer's left front wheel bearing had overheated and disintegrated, allowing the trailer wheel and tire to separate from the tractor front axle.
The root cause of the bearing failure was determined to be either inadequate wheel bearing lubrication, improper wheel bearing installation, wheel seal failure and/or defective wheel bearing manufacture.