As the demand for raw materials such as coal and metals grows to feed the thirsty, growing economies of China, India, Indonesia and elsewhere, everyone in the heavy mining industry is feeling the pinch of a tire shortage, including TransAlta, the Alberta, Canada-based firm that owns and operates the Centralia coal mine and adjoining coal-fired power plant.

"The tire shortage caught us all by surprise," said TransAlta mine manager Phil Jaramillo. "For years, the mentality in the industry was that tires are not an issue."

The tires that are in short supply are not your everyday road tires. These monsters weigh up to 12,000 pounds, sit 12 feet or more in diameter and support trucks that carry payloads of anywhere from 100 tons to 340 tons of coal, rock and dirt.

Keeping enough tires on hand for 50 mining trucks, road scrapers, road graders and loaders to work 24 hours a day, seven days a week at the Centralia mine is a $6.5 million annual task, representing one of the top five costs of operating the mine, Jaramillo said.

The three companies that supply tires for the world’s largest trucks – Goodyear, Michelin and Bridgestone – are having a hard time producing enough tires to meet international market demands, said Mel Jorgensen, tire and lubrication manager for the Centralia mine. It could be 2010 or later before production catches up with demand, he said.

So the truck drivers, heavy equipment operators and mine supervisors are under pressure to get as much life as possible out of each and every big tire used at the mine.

Some of the changes under way at the mine triggered by a short tire supply that first reared its head in 2004 include:

– Experimenting with tire sensors that are installed to measure pressure and temperature inside the tires.

– Setting haul profiles for each segment of the mine’s extensive road network. The longer the trip, the slower the truck travels to reduce heat buildup in the tires, Jorgensen explained.

"It’s a practice that flies in the face of faster is better for production," said Richard DeBolt, external relations manager for the Centralia mine and power plant.

In fact, slower is better, if it keeps a truck on the road and avoids costly down time in the truck fleet, Jorgensen said.

"It can take up to 16 hours to change out one of these tires," Jorgensen said.

– Paying more attention to how a truck is loaded, trying to keep the load balanced so tires on the overloaded side of the truck don’t overheat.

– Avoiding overloading a truck: rock and coal spilled on the haul roads can damage the tread and sidewalls of the tires.

– Switching to two-piece tires that allow new tread to be placed on older tire casings.

Traditionally, the company buys about 380 giant tires per year. The shortest-lived tires last about 3,500 hours.

"We’re trying to extend life expectancy by 10 percent to 20 percent," Jorgensen said. "I think it’s achievable."

So what happens when a tire does wear out?

The company historically had permits to bury the dead tires in the reclaimed areas of the mine.

But for the past 18 months, TransAlta has been sending its discarded tires to a Wyoming company that cuts the tires in half, fills them with cement and turns them into livestock water troughs.

Built 35 years ago by eight Pacific Northwest utilities, the Centralia power plant and coal mine is about five miles northeast of Centralia.

The power plant is the largest in Western Washington, capable of producing enough electricity for a Seattle-sized city.