Tire Spec’ing

Overdrive Staff | August 07, 2011

7. TIRE UNSUITED TO APPLICATION. All manufacturers rate their tires as to suitability for position and application. Only certain tires are designed to work in more than one position or application. The wrong tire or tread will not be nearly as durable as the right one.


PERFORM ROUTINE MAINTENANCE. Proper maintenance of tires, wheels, axles and the steering column will help keep your tire costs down. Wheels naturally lose alignment and balance. Bushings, shocks, bearings and valve stems wear out. Checking wheel alignment periodically can pay big dividends. Whenever you start seeing a heavy spot or a flat spot, the tire has ceased to be centered on the hub, and it’s beading out of round. Whenever you need to scrap a tire, inspect it to determine the cause of the failure, and record it.

The plungers inside shock absorbers create friction, and friction creates heat, so if the shock – not the outer dust barrel covering the top half of the shock – is hot to the touch after driving, it’s working. If it’s cool to the touch, it’s not working and should be replaced. Make sure bushings at the top and bottom of shocks are inspected and replaced whenever worn. If you can grab the shock absorber and rattle it, the bushings have pounded themselves out.

MAINTAIN PROPER INFLATION. Ironically, maintaining correct inflation is free and relatively easy, yet it’s the highest-saving maintenance you can perform on your truck. Improper inflation is by far the greatest reason why tires fail or wear out prematurely, also wasting fuel. Daily pre- and post-trip inspections give owner-operators the opportunity to check pressures and also look for leaks, punctures, broken valve stems or embedded objects such as nails. Metal valve caps tend to withstand wear and tear better than plastic ones. Even absent damage, truck tires typically lose one to two pounds of pressure a month from normal use. A slow leak such as a puncture might cost you one to three pounds of air a day.

Poor fuel economy isn’t the only cost of underinflation. Manufacturers design big-truck tires for a specific pressure, usually clearly specified on the sidewall. If the pressure’s too low, the sidewalls overflex and overheat. For each pound of air pressure lost, a tire’s on-road temperature rises about 2 degrees, and hot tires are prone to losing tread more quickly and failing. Don’t overinflate, either. An overinflated tire sustains rapid and irregular wear and is more susceptible to damage from running over debris and scrubbing curbs.

Some operators use aftermarket tire sealant products both as a safeguard against punctures and to help maintain proper inflation pressure. At least one tire manufacturer, too, markets a line of highway truck tires with sealant built-in from the factory. A quality sealant will have been extensively tested, and its dealer should be able to provide testing documentation. If you’re considering such a product, don’t hesitate to ask for this.

EMPLOY GOOD DRIVING HABITS. Speeding, hard braking, curbing and tight turns cause tires to wear faster or even develop irregular wear. On the other hand, steady acceleration, braking and steering can extend tire life. Many of the problems caused by bad driving habits show up as uneven tire wear. If you notice unusual shimmying or repetitive bumps, inspect your tires. Even absent rough driving, look for irregular tread wear in your daily inspections.

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