Feature Article: Seven tire killers

John Baxter | May 03, 2010

Seven tire killers



Tires, your biggest variable cost after fuel, cost a lot less per mile if they last as long as intended. Experts weigh in on the biggest threats to your tires.

 By John Baxter




1 Underinflation

A tire running on low air works “harder than it was intended to work. The tread rubber heats up,” says Guy Walenga, director of engineering for commercial products at Bridgestone/Firestone. Furthermore, the potential damage accelerates the further the tire gets from optimum pressure. For example, running 10 percent low means much more than a 10 percent increase in flexing, heat and damage from bending the steel cords beyond the point where they will spring back.

“You can never repair damage done to a tire this way,” Walenga says of overflexing. And “there is no tell-tale sign of damage. It may end up being useless for retreading.”

It also might be useless long before retreading. “Any commercial tire that has been run more than 20 percent underinflated must be considered flat and removed from the wheel to be inspected for damage,” says Matt Gudermuth, Continental Tire’s warranty manager for commercial vehicle tires. “Circumferential fatigue ruptures, known commonly as zipper failures, are caused by extreme deflection of steel casing cords during the load cycle of rotation, when the tire is underinflated or overloaded.”






This rupture results from excessive flexing and heat from underinflation or overloading. Not only do the steel cords bend beyond the point where they can easily spring back, but the heat weakens them and the other parts of the casing’s structure.

2 Overinflation or overloading

Overinflation can happen in these ways, says Jones:

• You put a significant amount of extra air in the tire to compensate for leakage. It’s always better to fix the leak and inflate the tire up to the proper pressure.

• You air the tire up on a cold morning and end up driving at high speeds after the weather warms significantly. Take time to check pressure in this situation and adjust as necessary.

• You’ve aired your tires for 80,000-pound running and then start hauling lighter freight. Instead, reduce the pressure according to the manufacturer’s recommendations for the axle loading.

When an object gets pinched between duals, it can damage the sidewalls enough that the cords and other parts of the casing are weakened and the casing made unrepairable. A regular tire inspection program that includes removal of such foreign objects will help with this problem.

3. Poor wheel alignment

“If the tires are not rolling straight down the road and straight up on the road surface, they are going to wear faster or in some sort of uneven way,” says Goodyear Marketing Communications Manager Tim Miller. “Today’s radial tires are designed to run such long distances before they wear out, any issue with toe, camber, caster and all axle perpendicularity to the chassis centerline will have a marked, negative effect.”

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