Three Wheels On My Wagon

"Surprise is the greatest gift which life can grant us."
-Boris Pasternak

Mater was driving some years ago, quite close to her home on a remote stretch of road, when she was suddenly overtaken without so much as a courteous tootle of a horn or a considerate flash of lights.
The offending item was a car wheel.
It was not attached to anything in particular and it looked suspiciously familiar as it hurtled past my astonished mother. The wheel trundled and bumped along the road for a prolonged and inexplicable moment, presumably out for an exploratory investigation of the world.
Being a vital component of Mater's car, the rubber delinquent was rendered useless without the three companion wheels. The vehicle, without the necessary fourth wheel, was equally lacking in balance: after the car came to a dramatic shuddering halt Mater was stranded. She was left alone to watch the renegade wheel roll on and recede into the distance until it ceased its little endeavour and staggered to a stop.
Mater arrived home some time afterward, safe and sound, albeit deliriously humming the tune of 'Three Wheels On My Wagon.'
A cursory investigation threw no light on why the wheel made an uncharacteristic attempt to live the life of an ambitious outlaw, and the case remains unresolved to this day.