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What Goes Around
Despite the preference among many drivers for new tires, hundreds of thousands of trucks run safely on retreaded tires, saving their owners thousands of dollars annually. Furthermore, they reduce the need for oil and keep scrap tires out of landfills and waste dumps.
It takes about 22 gallons of oil to manufacture a typical truck tire. The oil is converted to polymer compounds, each with specially engineered properties that match tire components to the tasks they must perform. Sidewalls must be flexible, yet resist abrasion. Treads must be flexible in one direction but resist squirming in two others. Shoulders must manage the transition from one to the other without breaking down. Liners must be soft enough to be pliable but must hold air pressure under all stress conditions. Beads must remain strong to secure the tire to its wheel while allowing flex in the transition to the sidewall.
Together, these areas are made from as many as 25 components, each of which provides one or more properties to the tire, with steel cords that are engineered to provide strength with either flexibility or controlled firmness. The polymer and, in some cases, natural rubber components form the body of the tire, its casing or carcass. The tread, which has no steel cords in it, is placed around the casing, and the entire assembly is put into a mold. Under heat and pressure, the tread pattern is precisely formed and vulcanized for strength and durability. Side markings that have the maker’s logo, load and maximum pressure information and the tire’s size are molded onto the tire during vulcanization.
Plumbing the depth
Unless a tire is physically damaged by curbing, potholes or road debris, most wear occurs at the tread surface. It is in constant contact with roads while transmitting braking, steering or acceleration. Uneven wear can be stopped and often corrected. Good maintenance and careful driving can limit tire wear to the tread.
Legally, drive and trailer tires must be removed from service when tread depth is down to 2/32-inches, and steer tires must be removed at 4/32-inches. Many owners scrap or trade their tires for new ones. Some even pay scrappage fees, although most reputable dealers will pay for retreadable casings: tires with no damage, as verified by X-ray and other inspections, and that have not been run flat.
Wise truck owners do not run tires to 2/32 for two reasons. Although fuel economy is very slightly improved when there is less tread mass to flex, wet weather traction suffers. Also, uneven tread wear can be buffed out only if there is enough tread left. The extra tread thickness creates a safety margin for the remaining casing to be retreaded.
If you prefer not to use retreaded tires, you can still help the environment, your fellow truckers and yourself by maintaining your casings in retreadable condition and turning them in to a dealer to be retreaded. Good casings have a residual value that can be put against the price of your next tires.
Another reason to turn in retreadable casings is that there is not nearly enough manufacturing capacity to fill the demand for truck tires with new or virgin product. In fact, if all the tire factories in North America went all out making tires, they would satisfy only about half of the current demand.
Retread myth busting
More than 30 years ago when I first entered the trucking industry, I used to hear drivers complain about “those darn retreads that throw rubber all over the highway.” The myth comes from the fact that early retreading techniques and quality did leave something to be desired. But inspection and manufacturing techniques as well as quality control have drastically improved over the years. And what are generally perceived as separated treads are, more often than not, the result of improperly maintained virgin tires, not retreads.
The tire does not support the vehicle. It contains the compressed air that does. The air also provides structural support to the tire, keeping its components operating in proper relation to each other. When there is too little air in the tire, it can flex excessively. Just as a paper clip heats when it flexes and eventually breaks, a tire’s components heat and can ultimately break. Internal air pressure limits flexing.
At designated pressure, a tire may heat to as much as 100 degrees Fahrenheit above ambient temperature, the heat of the road surface and surrounding air. That is well within the tire’s ability to remain stable. Lower pressures allow heating to 150 degrees or more. At elevated ambient temperatures, tire cords break and components break down, allowing the separation of components. We see them as “road gators” or “gator tails.” When examined, most have steel wires in them, a sure sign of damage due to under-inflation. Remember, the tread layer has no wire in it, so a tread separation would show no wire.
Some drivers will always prefer new tires, but if you’re considering retreads, remember that you’ll be in good company if you use them. They’re on vehicles operated by most major truck lines, the U.S. Postal Service, our Armed Forces, school buses, ambulances and fire trucks operated by most municipal, county and state fleets and jet aircraft operated by our major airlines.
- It takes only seven gallons of oil and no new steel cord to retread a tire, compared with the 22 gallons to make a new one.
- Retreading tires keeps used casings out of the environment.
- Because most of the tire is reclaimed, the cost of a retread is about half the cost of a new tire, saving owners thousands of dollars annually.