Goodyear Claims New Retreading Process Extends Tread Life
July 1, 2004
Many retreaders have adopted modern technology to improve the inspection and buffing processes. Once the casing has been inspected and buffed, they will typically use one of two different processes to apply the new tread:...
Many retreaders have adopted modern technology to improve the inspection and buffing processes. Once the casing has been inspected and buffed, they will typically use one of two different processes to apply the new tread:
Pre-cure – in which a section of vulcanized tread rubber is firmly bonded to a buffed casing and placed in a curing chamber where the tread becomes securely adhered to the tire.
Mold cure – where non-vulcanized tread rubber is applied to a buffed tire and the tire is heated in a mold, vulcanizing the rubber and forming a new tread design in it.
Each process has its advantages and disadvantages, according to Goodyear. The mold cure process has traditionally provided a high-quality product, but it requires expensive tooling and machinery, limiting the number of retreading facilities which can offer it and limiting the variety of tread designs.
The pre-cure process is more cost effective and offers more flexibility with tread selection. But care must be taken in how the tread is applied to the tire to ensure a balanced tire and even tread wear.
While pre-cure and mold cure have become standards, another approach has been gaining a foothold since it was introduced in 1996. Goodyear says its patented UniCircle process is being used to retread by a growing number of fleets and owner/operators
The UniCircle retreading system takes the best from pre-cure and mold cure processes and combines them into a cost-effective package, according to Goodyear.
“Technically, UniCircle is a pre-cure process,” says Ryan Searcy, Goodyear retread training center manager. “Most pre-cure processes use a section of tread which is laid onto the buffed tire and the two ends must be joined. UniCircle uses a tread section which has already been molded into one circular piece and is stretched over the buffed casing like a giant elastic band. The compounding and patterns used for the UniCircle treads is identical to those used on new Goodyear tires, providing similar wear and rolling resistance qualities. The operator also gets a wider choice of treads to choose from.
“To create the tread, a precise amount of non-vulcanized rubber is placed into a mold and is then cured for a specific time at a designated temperature and pressure,” continues Searcy.
“Using laser guidance, the tread is automatically positioned on the casing and is then precision-stitched. Once it’s cured, the finished UniCircle retread has no seam. It looks and performs almost identical to a new tire.”
Searcy says the precise positioning of the tread on the casing and the seamless fit benefit the tire user in a number of ways. “This retreading process is really the wave of the future,” said Searcy. “Truck operators are experiencing longer tread life with UniCircle because the tire runs truer and the tread wears more evenly. And, since there is no splice, the tires are easier to balance.”
Searcy says users also benefit from UniCircle tread in the way it adheres better to the casing. “A tighter fit means better traction and also reduces tread tearing and chunking. Any time the tread starts getting damaged that way, you will shorten its life significantly and you may even end up scrapping a casing earlier than you want to.”
Searcy says UniCircle has been growing faster than the retread industry as a whole since its introduction and Goodyear plans to continue to add UniCircle production capacity.
“UniCircle does a lot to extend tread life and protect casings – the two biggest keys to lowering tire cost per mile,” Searcy concludes. “When you combine that with the improvements that have been made to casings over the past few years, such as Goodyear’s Enhanced Casing Design, retreads make a lot more sense for many truck operators. There’s a definite payback there.”
THE EVOLUTION OF RETREADS
Every year, more than 33.5 million tires on North American commercial vehicles wear out and must be replaced. Of those, around 16.5 million, or 49%, will be retreads.
Many fleets favor retreads over new tires because it makes economic sense. The cost of a retread is typically 30% to 50% lower than a new tire.
In addition, the quality of retreads has improved in recent years to the point where they provide comparable life and performance to new tires. “In the 1960s and 70s, treads would wear out in 60,000 to 70,000 miles,” according to retreading expert Marvin Bozarth, former executive director of the American Retreaders Association and a recent inductee into the Tire Industry Association Hall of Fame. “Now a retreaded tire can go 200,000 miles or more, depending upon the wheel position and application. The tire construction has improved and today’s tread compounds are more resistant to heat so they wear better.”
The history of retreading goes back almost as far as the manufacturing of tires themselves. In the 1890s, early automobile users were already using patch kits to cement rubber sections onto damaged sections of tires. By 1904, a patent had been issued for the use of vulcanization changing the property of the rubber patch to create a permanent bond to repair tires. This would pave the way for the eventual vulcanization of entire new sections of tread onto worn tires.
While it may not have been as revolutionary as other tire milestones such as the discovery of vulcanization by Charles Goodyear in 1839 and the first pneumatics by John Dunlop in 1888, retreading has saved users more money than any other tire innovation.
The demand for retreads in North America grew in the 1950s as the trucking industry matured and became the dominant mode of freight transport. With tires ranking number one in equipment maintenance costs, fleets quickly realized the value in retreading a casing they already owned rather than replacing it with a new tire each time.
Retread sales have grown steadily over the past few decades as product quality has improved and fleets have had access to better tools to integrate them into their tire programs.
The three basic elements of retreading – time, temperature and pressure – haven’t changed,” said Bozarth. “What has is mechanization of the processes and the improvement of tire construction and tread compounds.”
Bozarth said tire inspection systems used by modern retreaders are far better than they used to be, making it quicker and easier to identify damage and repair it.
“Computerization and more precise machinery has helped extend casing life,” he said. “When tires come in for retreading, they can be buffed more smoothly to provide a better tread mounting surface. Everything is consistent and repeatable.”mt
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