They’re round and black, radial or bias. Other than size, tread patterns and a few secret ingredients, tires don’t vary that much.
But Goodyear changed all that Wednesday at the Kennecott copper mine near Salt Lake City with the introduction of a radical new concept in tires for big, off-road haul trucks. The new design, three years in the making, is so different that company officials prefer not to call them tires but rather “two-piece assemblies.”
The two pieces consist of a pneumatic casing and a tread belt. The tread belt slips over the casing. As the casing is inflated, the two pieces are pulled into alignment and held together by interlocking grooves.
The two-piece design offers numerous advantages over conventional tires, says Tom Walker, global general business manager for OTR tires. To start, truck maintenance crews don’t have to remove the wheel rim (and as many as 72 lugnuts) to change tires. After the tread wears out you simply deflate the casing, slip the old tread off, slip the new tread on and reinflate the casing. The casing and wheel stay put and a specially designed bead-seat band clamp keeps the bead intact and sealed during changes.
The change takes about a half hour per assembly and cuts the process of changing a set of truck tires from an all-day task to as little as three hours. Plus you don’t have to go through the process of adjusting and retorquing the wheels after a tire change.
The reduction in downtime also makes it easier to react to changing ground conditions. If your site’s underfoot conditions change due to rain or seasonal weather, or you move to a different site, changing the tread belt is more cost efficient than changing the entire tire or halting production until conditions improve.
Walker says he anticipates the typical casing will last through two or three tread belts, providing some cost efficiency when compared with tires that are used once and then disposed. Tire transportation and storage costs are also reduced since the tread package can be folded nearly flat and shipped on standard-size trailers.
Beyond the cost and quick-change benefits, Goodyear’s two-piece assemblies offer substantial performance benefits over conventional tires, Walker says. The footprint is about 11 percent larger and 20 percent more uniform for improved traction and flotation. The larger ground contact area also improves the tread wear rate, penetration resistance and lateral stability. And the tread belt is also slightly wider than the casing, so the lip formed by the tread at the edge of the tire helps deflect rocks and debris that cause sidewall cuts. When the tread is torn or punctured, those incursions won’t grow or migrate from the tread into the casing.
The two-piece assembly also runs cooler than conventional tires since less heat is transferred from the tread belt to the casing. And since the tread belt and casing are manufactured separately, the company can optimize the rubber compounds for each.
Goodyear is currently offering the two-piece assembly in a 45R57 size. Next year a 51-inch size will be introduced, followed by a 63-inch version in 2005. Current applications are limited to haul trucks but the company will be exploring wheel loader applications in the future.