Putting it plainly, if tiremakers could make giant earthmover tires as fast as they can produce passenger tires, they would. Especially right now, when every mine, quarry and construction site around the globe is begging for fresh rubber.

But the fact is that producing one of these 45- to 63-inch behemoths is an arduous task that taxes engineer brains and physical equipment alike. This is why Michelin North America (MNA) – and Groupe Michelin worldwide – is shoring up its OTR tire capacity, a series of moves that culminated last month with the announced expansion of MNA’s Lexington, S.C., OTR plant.

The $85 million Lexington project will add eight curing presses to the factory. While eight presses doesn’t sound like much, the 50% increase in capacity will add an estimated 4,300 tires to the plant’s annual output. Some 45% of the Lexington plant’s tires are exported, according to MNA officials.

Globally, Michelin is adding an all-new OTR tire plant in Brazil, slated to begin production in late 2007, and is expanding its giant OTR plant in Vitoria, Spain. The 34% in added capacity will make a dent in a market that has been overrun by a number of factors, including construction demands in China, India and other countries; high commodity mineral prices that has boosted output at gold, silver, copper and other mines; and infrastructure rebuilding in the wake of natural disasters in the U.S.

It’s little wonder Michelin is expanding the eight-year-old facility. According to MNA officials, every tire built there in 2005 was sold before the first tire component was extruded. And, the same holds true for 2006.

The highly automated Lexington plant employs 250 people, said MNA, and has some 500,000 square feet under roof. The capacity addition will mean more physical structure, but because the final plans are not yet completed, MNA officials could not pinpoint the amount of square footage being added. Even without final blueprints, plant manager Sarah Miller said that ground is already being prepped for the expansion.

“Decisions to radically expand plant capacities don’t happen in a vacuum,” said MNA chairman and president Jim Micali in announcing the expansion. “At the core of the opportunity are Michelin employees here in Lexington…Their hard work and talents played a large role in the decision to invest even more here in Lexington.

“The investment we are making now will position Michelin to quickly respond to further growth in the large mining tire market, as demand for Michelin earthmoving tires continues to increase at a phenomenal rate,” Micali said.

Inside Production

While quick response is the objective, there are few ways to hasten the production process. It takes anywhere from 48 to 64 hours to produce one giant OTR tire, from mixing to component extrusion to building through curing and final inspection.

Giant OTR tires at Lexington are made pretty much like other tires; they just need larger machines and more time.

With no Banbury mixer on site, pre-mixed rubber stock is brought in from other MNA facilities. Once at Lexington, the raw stock is processed through a series of extruders. Gigantic beads are wound and bound on site and wrapped completely in rubber.

Green components then make their way to the two-stage building equipment area. On one side, tire builders lay down the innerliner, carcass plies and beads. Huge cradles are needed to transport each completed first-stage “product” across the aisle to one of 14 second-stage builders.

Computer-controlled, second-stage builders add sidewalls and an array of reinforcement plies and protector strips. Finally, tread stock is spiral wound around the circumference until the desired thickness is reached.

Robotic transporters move the huge green tires to the curing room, where a monstrous overhead crane system moves each green tire to its intended slot. Hours later, the still curing tire is removed from the press and carried overhead to a conveyor, where it will sit and cool until it can be moved to final inspection.

Each tire produced at Lexington is hand inspected and then x-rayed. Of course, given the pace of the plant, there’s plenty of time to QC each unit.

While the pace of the OTR plant doesn’t match the orchestrated frenzy of a passenger tire facility, the goal is the same – to produce quality tires as fast as possible. The added capacity at Lexington, said Michelin, will allow it to do just that.