STRANGE

Things

Can a load be too light?

Sometimes, a very light load, coupled with too high a speed, can destroy a tire. Often, this occurs on dynamometers. (You’ll find recommendations for dyno testing on page 84 of the Bridgestone data book.) With light loads, the footprint can be tiny, and heat will concentrate in it. High heat can degrade the tread rubber, creating the soft, spongy texture you see here. A tread like this will also feel “spongy” to the touch. Thick 31¼32" treads, as on this L317, are especially prone to heat buildup. That’s why usage of most L317s is limited to maximum sustained speeds of 55 mph. But this tire has never been on a dynamometer. It was taken from a brand new vehicle. And the damage occurred during delivery. You’ve probably seen new tractors being hauled “piggy-back” style. Often, only the rear drive tires are on the ground. There’s very little load, and even though the hauling vehicle could run at maximum legal speeds, if the driver goes over the maximum allowable sustained speed for the tires on the new tractors, the treads can be “cooked.” That’s what happened here.

Practically brand new, this L317 heavy lug radial is already ruined, the victim of too high a speed and too little load.