Tire Spec’ing

Overdrive Staff | August 07, 2011

USE RETREADS. Premium tires cost $300 to $600 new, while retreads average about $200. Retread casings are tested via road use and by shearography, laser scanning that detects virtually any flaw. The same research and development that keeps new tires ever more durable and fuel-efficient is being introduced to retreads.

Premium tire makers design casings for retread use. Theoretically, undamaged casings can be often retreaded, although the tire maker’s casing warranty might expire at, for example, 750,000 miles or after three retreadings. On the downside, some carriers and state governments restrict retread use on steer axles. And not all retreads are created equal. If the retread isn’t from a reputable dealer, or if its markings have been scrubbed off the side, think twice before buying.

USE WIDE SINGLES. Wide singles weigh less and save fuel. They also cost less than the two tires they’re designed to replace, although you have to buy new rims to get in the game. Wide singles are retreadable, too.

A retrofit of wide singles on your tractor’s drives will cost an estimated $4,400. That covers four new wheels at $350 or more each and tires that run around $750 apiece. With a fuel-efficiency gain of 4 percent due to the reduced rolling resistance singles offer, though, the fuel savings will pay for the new wheels and tires in about two years. If you’re in a payload-sensitive application, the weight savings could yield bigger revenue, reducing that time period dramatically.

GO LOW-PRO. For long-haul, on-highway applications, a low-profile tire set-up with a shorter height than width offers fuel-efficiency, handling, weight, overall truck height and tire life advantages over more standard configurations. The aspect ratio – sidewall height measured in a percentage relative to its width at its widest point – of the most common 11R22.5 tires is about 100 percent, meaning the sidewall height and width are the same. Low-pro tires’ aspect ratio is around 80 percent, with size designations such as 295/75R22.5.


SEVEN TIRE KILLERS

Avoid these most-common tire threats to keep costs low.

1. UNDERINFLATION. A tire running on low air works harder than it was intended to. The potential for damage accelerates the further the tire gets from optimum pressure. If it doesn’t fail, the tire could end up being useless for retreading.

2. OVERINFLATION OR OVERLOADING. Overloading a tire produces problems similar to those of underinflation. Never load a tire beyond its rating. Instead, adjust air pressure for the load and/or ambient temperature. Hot temperatures increase air pressure; cold reduces it.

3. POOR WHEEL ALIGNMENT. If wheels aren’t aligned correctly, tires aren’t rolling straight down the road, and wear will accelerate. This can happen to the point where the tread wear cuts into the casing and even the cords. At that point, the tire is nothing but scrap. Keep in mind that total vehicle alignment is important in this regard. A trailer that’s “dog-tracking,” or running with the rear to one side, will wear the tires on the tractor, too.

4. POOR SUSPENSION MAINTENANCE. Neglect of the suspension system will create a snowball effect, with the tire facing uneven stresses that change every few seconds, as well as a suspension system that simply cannot be brought to spec. Key suspension maintenance activities include: frequent greasing (at least twice every oil change) and inspection of tie rods, king pins, bushings and the like for looseness.

5. IMPROPER MOUNTING OR DE-MOUNTING. This would include using starting fluid, tools with rough edges, failing to clean the wheel or inspect it to make certain it hasn’t been damaged or over-stressed, and replacing the core seal rather than re-using the old one.

6. IMPROPER REPAIR. Never allow a rope (patch) repair to serve as a permanent fix to a punctured tire. The tire should be removed soon after and inspected, and the inner liner resealed.

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