Retread (also known as recap or remold) is a re-manufacturing process for tires that replace the tread on worn tires. [1] [2] Retreading is applied to casings of spent tires that have been inspected and repaired. [3] It preserves about 90% of the material in spent tires and the material cost is about 20% compared to manufacturing a new one.
Some applications for retreaded tires are airplanes, racing cars, buses and delivery trucks. Use of retreaded tires was common historically, but as of 2008, it was seldom used for passenger vehicles, mainly due to discomfort on the road, safety issues and cheaper tire brands surfacing on the market. About 17.6 million retreaded tires were sold in North America in 2006. [4]
There are two main processes used for retreading tires, called Mold Cure and Pre Cure. Both processes start with the inspection of the tire, followed by non-destructive inspection method such as shearography to locate non-visible damage and embedded debris and nails. Some casings are repaired and some are discarded. Tires can be retreaded multiple times if the casing is in usable condition. Tires used for short delivery vehicles are retreaded more than long haul tires over the life of the tire body. Casings fit for retreading have the old tread buffed away to prepare for retreading. [4]
Material cost for a retreaded tire is about 20% that of making a new tire. [3] About 90% of the original tires by weight is retained in retreaded tires. A 1997 study estimates that then current generation of commercial vehicles tires to last up to 600,000 miles if they're retreaded two to three times. [5]
Previously prepared tread strip is applied to tire casing with cement. This method allows more flexibility in tire sizes and it is the most commonly used method, but results in a seam where the ends of the strip meet. [4]
Following a thorough quality inspection, the worn tire tread is removed from the casing by buffing. [6] Raw rubber is then applied to the tire casing and it is then placed in a mold where tread is formed. A dedicated mold is required for each tire size and tread design. This tread application method is very similar to that of the new tire manufacturing process.
In this subtype, retreading is also applied to the side walls. [7] These tires are given entirely new branding and stamps. [4]
Some jurisdictions have regulations concerning tire retreading.
In Europe all retreads, by law, must be manufactured according to EC Regulation 108 (car tires) or 109 (commercial vehicle tires). As part of this regulation all tires must be tested according to the same load and speed criteria as those undergone by new tires.
The Land Fill Directive of 1999 banned tires in landfills in 2003, and banned shredded tires in 2006. [3]
The Department of Transportation requires marking of a "DOTR number" which shows the name of the retreader and when it was retreaded. [4]
The United States National Highway Traffic Safety Administration recognizes the public perception that retread tires frequently used by heavy vehicles are less safe than new tires as evidenced by tire debris frequently found on highways. The NHTSA is continuing research to determine the proportion of tire debris from retreads in comparison to new tires. Additionally, the NHTSA is researching the cause of tire failure and the crash safety problem posed by tire failures. [8]
Federal Executive Order 13149, signed by President Bill Clinton supports the use of retread tires for economic and environmental efficiency by requiring federal vehicles to use retread tires after original factory equipped tires become non serviceable, but only when "such products are reasonably available and meet applicable performance standards".
Retread tires in service lower the volume of raw materials required for the manufacturing of a new tire. This includes a pronounced reduction in the use of oil. In fact, the US EPA estimated a greater than 75% savings in oil used for a retread as compared to a new tire. This also means significant reductions in greenhouse gas emissions. A car tire has 40% natural rubber and 60% oil based rubber, a retreading of tires will reduce the need for natural rubber significantly.
In addition to reducing the amount of raw materials extracted, retread tires also minimize the amount of waste that ends up in landfills. The latest figures by the US EPA indicate that over 11.2 M waste tires were dumped into the U.S. municipal solid waste stream. To understand this figure, it is equivalent to lining up passenger tires tread to tread from roughly Los Angeles to San Diego or Philadelphia to Washington DC. Because a retread tire prevents the need for manufacturing a new tire, significant environmental benefits are achieved. [9]
A tire is a ring-shaped component that surrounds a wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide traction on the surface over which the wheel travels. Most tires, such as those for automobiles and bicycles, are pneumatically inflated structures, providing a flexible cushion that absorbs shock as the tire rolls over rough features on the surface. Tires provide a footprint, called a contact patch, designed to match the vehicle's weight and the bearing on the surface that it rolls over by exerting a pressure that will avoid deforming the surface.
The Firestone and Ford tire controversy of the 1990s saw hundreds of people die in automobile crashes caused by the failure of Firestone tires installed on light trucks and SUVs made by Ford Motor Company.
Municipal solid waste (MSW), commonly known as trash or garbage in the United States and rubbish in Britain, is a waste type consisting of everyday items that are discarded by the public. "Garbage" can also refer specifically to food waste, as in a garbage disposal; the two are sometimes collected separately. In the European Union, the semantic definition is 'mixed municipal waste,' given waste code 20 03 01 in the European Waste Catalog. Although the waste may originate from a number of sources that has nothing to do with a municipality, the traditional role of municipalities in collecting and managing these kinds of waste have produced the particular etymology 'municipal.'
Crumb rubber is recycled rubber produced from automotive and truck scrap tires. During the recycling process, steel and tire cord (fluff) are removed, leaving tire rubber with a granular consistency. Continued processing with a granulator or cracker mill, possibly with the aid of cryogenics or by mechanical means, reduces the size of the particles further. The particles are sized and classified based on various criteria including color. The granulate is sized by passing through a screen, the size based on a dimension or mesh. Crumb rubber is often used in artificial turf as cushioning.
Siping is a process of cutting thin slits across a rubber surface to improve traction in wet or icy conditions.
Radial force variation or road force variation (RFV) is a property of a tire that affects steering, traction, braking and load support. High values of RFV for a given tire reflect a high level of manufacturing variations in the tire structure that will impart ride disturbances into the vehicle in the vertical direction. RFV is measured according to processes specified by the ASTM International in ASTM F1806 – Standard Practice for Tire Testing.
Automotive tires are described by an alphanumeric tire code or tyre code, which is generally molded into the sidewall of the tire. This code specifies the dimensions of the tire, and some of its key limitations, such as load-bearing ability, and maximum speed. Sometimes the inner sidewall contains information not included on the outer sidewall, and vice versa.
Pneumatic tires are manufactured according to relatively standardized processes and machinery, in around 455 tire factories in the world. With over 1 billion tires manufactured worldwide annually, the tire industry is a major consumer of natural rubber. Tire factories start with bulk raw materials such as synthetic rubber, carbon black, and chemicals and produce numerous specialized components that are assembled and cured.
A tire-pressure monitoring system (TPMS) monitors the air pressure inside the pneumatic tires on vehicles. A TPMS reports real-time tire-pressure information to the driver, using either a gauge, a pictogram display, or a simple low-pressure warning light. TPMS can be divided into two different types – direct (dTPMS) and indirect (iTPMS).
Rubber mulch is a type of mulch used in gardening and landscaping that is made from recycled rubber, most often crumb rubber sourced from waste tires.
Waste diversion or landfill diversion is the process of diverting waste from landfills. The success of landfill diversion can be measured by comparison of the size of the landfill from one year to the next. If the landfill grows minimally or remains the same, then policies covering landfill diversion are successful. For example, currently in the United States there are 3000 landfills. A measure of the success of landfill diversion would be if that number remains the same or is reduced. In 2015 it was recorded that the national average of landfill diversion in the United States was 33.8%, while San Francisco had implemented the most effective policies and had recorded a landfill diversion rate of 77%.
A release agent is a chemical used to prevent other materials from bonding to surfaces. Release agents aid in processes involving mold release, die-cast release, plastic release, adhesive release, and tire and web release. Release agents are one of many additives used in the production of plastics.
There is no national law in the United States that mandates recycling. State and local governments often introduce their own recycling requirements. In 2014, the recycling/composting rate for municipal solid waste in the U.S. was 34.6%. A number of U.S. states, including California, Connecticut, Delaware, Hawaii, Iowa, Maine, Massachusetts, Michigan, New York, Oregon, and Vermont have passed laws that establish deposits or refund values on beverage containers while other jurisdictions rely on recycling goals or landfill bans of recyclable materials.
Snow tires, also known as winter tires, are tires designed for use on snow and ice. Snow tires have a tread design with larger gaps than those on conventional tires, increasing traction on snow and ice. Such tires that have passed specific winter traction performance tests are entitled to display a 3PMSF and/or a IMP symbols on their sidewalls. Tires designed for winter conditions are optimized to drive at temperatures below 7 °C (45 °F). Studded tires are a type of snow tires which have metal or ceramic studs that protrude from the tire to increase traction on hard-packed snow or ice. Studs abrade dry pavement, causing dust and creating wear in the wheel path. Regulations that require the use of snow tires or permit the use of studs vary by country in Asia and Europe, and by state or province in North America.
Tire uniformity refers to the dynamic mechanical properties of pneumatic tires as strictly defined by a set of measurement standards and test conditions accepted by global tire and car makers.
Tire recycling, or rubber recycling, is the process of recycling waste tires that are no longer suitable for use on vehicles due to wear or irreparable damage. These tires are a challenging source of waste, due to the large volume produced, the durability of the tires, and the components in the tire that are ecologically problematic.
Road debris, a form of road hazard, is debris on or off a road. Road debris includes substances, materials, and objects that are foreign to the normal roadway environment. Debris may be produced by vehicular or non-vehicular sources, but in all cases it is considered litter, a form of solid waste. Debris may tend to collect in areas where vehicles do not drive, such as on the edges (shoulder), around traffic islands, and junctions.
Products made from a variety of materials can be recycled using a number of processes.
Resource recovery is using wastes as an input material to create valuable products as new outputs. The aim is to reduce the amount of waste generated, thereby reducing the need for landfill space, and optimising the values created from waste. Resource recovery delays the need to use raw materials in the manufacturing process. Materials found in municipal solid waste, construction and demolition waste, commercial waste and industrial wastes can be used to recover resources for the manufacturing of new materials and products. Plastic, paper, aluminium, glass and metal are examples of where value can be found in waste.
The following outline is provided as an overview of and topical guide to tires:
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