Five tips to control your tire costs and improve vehicle performance, safety
Sep 1, 2008 12:00 PM
With tires ranked as the second highest operating cost after fuel, a solid tire maintenance program can help reap solid dividends. “It could add thousands of dollars to your bottom line, thanks to longer tread life and more retreads down the road,” says Goodyear commercial tire marketing manager Tim Miller. “Add in good driving habits - smooth acceleration, braking and steering - and you have the recipe for lower maintenance and tire costs.”
Miller has five tips for controlling tire and vehicle costs:
- Tire inflation pressure
The top priority is maintaining tire inflation pressure. Premier fleets that conduct tire surveys find more than 95% of their tires are within tire inflation specifications. They check tire pressures when trucks are in for service; their drivers check inflation at least once a week; and it's common for their tire representatives to help them with yard inflations and checks. Moreover, premier fleets don't use thumpers; only calibrated tire gauges will do. Studies have shown that thumpers give you a false sense of security.
Harvey Brodsky, from the Tire Reread Information Bureau, has held many tire thumping contests to see if drivers can accurately tell if a tire is underinflated. The result?
“Trying to determine how much air is in a tire by thumping is the same as trying to determine if a truck's engine needs oil by thumping the hood,” says Brodsky. “In a recent contest, only one out of more than 50 participants was able to guess the tire with the correct amount of air.
“The only way to properly check the air pressure in a tire is with a properly calibrated tire gauge. Anything else is just a guess, and one that can be very expensive if the thumper guesses wrong. Tires that are run underinflated stand the risk of not being retreadable after the initial tread is worn off.”
A Technology and Maintenance Council (TMC) tire-failure study showed that under-inflation caused 90% of all tire failures. Under-inflation causes tires to flex more as they travel and generate rubber-damaging heat inside the tires. A tire under-inflated by 20% loses 30% of its life. When inflation drops 40% below the recommended level, the tire lasts only half as long.
Knowing the proper inflation level for your truck tires is crucial. TMC Recommended Practice (RP) 235 states the following determines the correct air pressure for a given load:
Tire size and load rating
Weight carried on each axle
Number of tires on each axle
Maximum speed the vehicle travels during its operation
(Note: Your tire manufacturer's data book or the Tire and Rim Association's Yearbook provides load, speed and inflation tables for a given size and type of tire.)
Whatever you do, don't guess on tire inflation pressures. Tire dealers can help calculate the correct numbers to carry the load. Armed with proper inflation pressures for your trucks, you can maximize the performance engineered into your tire.
- Periodic tire inspections
A pre-trip inspection can help catch a lot of issues that can lead to downtime and premature tire life down the road. Visually inspect the tread and sidewall of all the tires for obvious under-inflation and objects that may be lodged in the tread or sidewall. Examine the tread and feel the rubber with your fingertips for imperfections, irregular wear pattern, or feathering of the tread blocks. Fingertips are very sensitive to changes in patterns and unusual wear.
- Total axle alignment
When your truck runs straight down the road, the chances of fast or irregular tire wear are minimized. A traditional front-end alignment is insufficient. Drive axles must be inspected to ensure that they are perpendicular to the chassis, and for tandem axles, parallel to each other. If drive axles are out of alignment, drivers must constantly turn the steer tires right and left to keep the truck tracking straight down the road. Fast steer-tire wear results.
Out-of-alignment trailer axles similarly can wear tractor steer and drive tires as well as trail tires.
- Worn components
To make the most of a realignment, technicians should check for worn king pins, bearings, and steering components. Before checking axle alignment, tolerances for each component must be in spec. Excessive movement in any component helps lead to fast and irregular tire wear.
In addition, shock absorbers should be inspected for wear. A worn shock is an open invitation for irregular wear patterns. Air-ride suspensions make it paramount that the shocks are adequate for the job, and they must be replaced when worn.
- Rotate tires to maximize casing life
Tires should be rotated, particularly in slow wear-rate situations, for more miles to removal. If you own trailers, it's recommended that you remove steer tires at 6/32nds to 8/32nds and run them on your trailer axles down to 4/32nds to achieve optimum uniform wear prior to retreading. Retreaded steer tires should be moved to the drive axles and run to 4/32nds. At that point, the second retread can be installed on the trailer.
Meanwhile, you should remove new drive tires at 4/32nds in linehaul service. The first retreads can be re-installed on the drive axle; the second retreads can be used on the trailer.
For tires in a mixed-service application or in situations where stones are stuck in the grooves, continuous inspections are necessary for possible tire damage. In these cases, drive tires should be removed for retreading at 6/32nds. Trailer tires should be retreaded at 3/32nds to 4/32nds. First retreads can be run as drive or trail tires, while second retreads should only be used as trail tires.
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