What goes around
Next to fuel, tires are your biggest vehicle-operating cost. Making poor choices when selecting your tires often results in higher costs for you in the long run, even if they seem more cost efficient at the time you purchase them. Tires are designed for specific applications and uses. They offer advantages and disadvantages depending on your vehicle design and expected duty cycle.
To keep your overall tire costs down, you should try to match tires as closely as possible to your specific application.
While most new tires sold today are radials, you can still purchase bias ply tires. A bias ply tire gets its name from its design of overlapping crossed layers of cord material, typically made with nylon, polyester or other materials. The crossed plies run diagonally all the way from one tire bead to the other. Extra plies are sometimes used under the tread area to stiffen the crown area and make the tire more resistant to punctures. Bias ply tires also tend to have stiffer sidewalls and can handle more punishment when hitting objects. If you are expecting to spend a lot of time off-road in areas where there are a lot of rocks and other obstacles, bias ply tires may be the best choice. These tires also offer better feel and handling, and they're less expensive than radials.
However, radial tires have become more durable and can be used in a lot of mixed service applications. Radial tires are so-named because they have cord material running in a radial or direct line from the bead. They typically have one steel body ply or multiple plies of other materials. While radial sidewalls are not as stiff as bias ply sidewalls, the tread area of a radial offers more rigidity. This provides you longer tread life, more resistance to tread-area punctures and better fuel-efficiency than bias ply.
Radials tend to run cooler than bias ply, so if you will be driving extended periods on-highway, radials will be your best choice. “Heat is the tire's enemy,” says Al Cohn, manager of training and technology for Goodyear Tire Co. “The more you can do to keep a tire running cooler, the longer the life of the tire.”
KEEPING A LOW PROFILE
If you are loading and unloading lawn equipment often, it's in your best interest to get the deck height down. Doing so will result in your equipment operators not having to lift as high, and your ramps won't need to be as steep, either.
“You can get the deck height down with low profile tires,” says Goodyear's Cohn. “These are tires which are basically wider than their section height. The ratio of section height to section width is usually between 70 and 80 percent.”
The downside is that you are at greater risk of sidewall damage from curbs and other solid objects. “You also need to be aware of the impact on your truck's drivetrain and gearing,” says Cohn. “A smaller tire will rotate faster than a standard size tire at the same speed. To stay fuel-efficient, you may need to adjust the transmission and rear axle ratios so the engine rpm isn't too high at highway speeds. As a general rule, you should make a gearing change if the tire rpm changes 3 percent or more.”
Tires play a crucial role in supporting the vehicle's load, so it's important that you consider maximum axle loading when you're outlining your tire specifications. All tires have specific load limits at defined speeds and inflation pressures. The Tire and Rim Association has established these limits and publishes them in tables. They are also available through tire manufacturers.
To figure out what tire you need, you first determine the maximum expected loads at the wheel position. Then look at the tables, find your tire size and look up the load that is close to, but slightly more than, the maximum anticipated load. The tables profile loads for both single and dual applications.
WATCH AIR PRESSURE
Without air, tires have no load-bearing capacity. “It's air that actually supports the load, not the tire itself,” says Cohn. “That's why it's important to maintain the inflation pressures shown in the load tables.”
Each tire is rated at a specific load, based on inflation pressure. The lower the pressure, the lower the weight it can carry. Underinflation also leads to higher heat, greater risk of premature tire failure and reduced mileage. “A tire that is 20 percent underinflated will result in 16 percent fewer miles to removal,” Cohn says.
Overinflating is not recommended either. It will give drivers an uncomfortable, bouncy ride and the tires will develop excessive centerline wear, resulting in early removal.
The type of tread you select can have a significant bearing on your overall tire costs. A block-type tread is good for traction on drive wheels, but it will increase the vehicle's rolling resistance and increase fuel usage.
“The deeper the tread, the more flex there will be,” says Cohn. “More flex generates more heat, and that's what hurts fuel mileage.”
You should choose a tread that best suits the terrain you will be operating in and your mileage goals, says Cohn.
Retreading tires is a great way to cut overall tire costs. Tire casings, which can be recycled two, three or more times, provide savings in a number of ways.
“The key to successful retreading is protecting the casing,” says Cohn. “The casing's two biggest enemies are heat buildup and moisture penetration. Heat buildup is caused mostly by running underinflated or overloading the vehicle, or both. When moisture gets into the tire, the steel-belt package rusts and the tire's structural integrity goes.”
GETTING IT RIGHT
While all of these elements may seem like a lot to take into consideration just to pick out some tires, this extra effort will pay dividends in the long run. By selecting the right tires for the job, you'll not only see less down time, you'll see a cost savings and bigger profit margin.
PROLONGING TIRE LIFE
No matter how carefully you select your tires, how you treat them will have the biggest influence on how long they will last. Here are five tips from Goodyear to extend tire life:
Check tire pressure daily using a gauge that's been calibrated from a master gauge. If you run dual rear tires, don't forget to also check the inside duals.
Train drivers to accelerate and decelerate gradually. Quick starts and hard braking generate excessive heat, shortening the life of the casing.
Don't speed. For every mile per hour driven over 55 mph, tread life is reduced 1 percent.
Take it easy on corners. High-speed cornering scuffs the tread, leading to premature wear and early tire removal.
Avoid hazards such as potholes, curbs and rocks. Running over them can lead to irreversible sidewall damage and chunking.
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