What’s “eating” this tire?

This tire has a bunch of holes in it. It looks as if termites have been gnawing at it or maybe it’s infested by worms. But modern truck tires are made of pretty tough stuff – that’s not appetizing to either termites or worms.

So what could it be? Well, there’s a clue in the marks near the holes. Looks a little like tree branches – or maybe like those photos you see of lightning strikes.

As it turns out, it was electricity that “burrowed” through this tire. We think of rubber as an insulator, but even insulators will conduct electricity if the voltage is high enough.

That’s what happened here. A boom truck grazed some overhead high voltage lines, and the electricity traveled right through the metal of the truck to the tires. The voltage was high enough that the current traveled through the rubber, emerging from it to reach the ground.

In the process, it created enormous heat, boring tunnels through the tire. As it escaped from the rubber, sparks burned a fine, tree-branch pattern into the surface of the tread.

Although the vehicle operator was unharmed, because of massive internal damage, this tire will have to be scrapped.