The Rubber Manufacturers Association (RMA) has sent a letter to the National Highway Traffic Safety Administration (NHTSA) urging the agency to evaluate any relevant information concerning tire service life and to issue a consumer advisory on proper tire care.
The RMA requested that the letter be added to NHTSA docket number 2005-21276.
The RMA and its member companies "are not aware of any factual or scientific data that define a relationship between tire service life and tire safety performance," says an RMA spokesman.
(RMA's membership includes all of the country's major tire manufacturers: Bridgestone Firestone North American Tire LLC, Continental Tire North America Inc., Cooper Tire & Rubber Co., Goodyear Tire & Rubber Co., Michelin North America Inc., Pirelli Tire North America Inc. and Yokohama Tire Corp.)
"As the regulatory agency charged with protecting consumers and advancing highway safety, NHTSA is well-suited to ensure that any message to consumers about the service life of a tire is based on sound science and is fully supported by data that can be validated by the agency," he says.
"In the absence of any such data, and until this issue is resolved, RMA is asking NHTSA to issue a consumer advisory on proper tire care."
Here is the letter, from RMA CEO and President Don Shea to NHTSA Administrator Jeffrey Runge, in its entirety.
The Rubber Manufacturers Association (RMA), the leading trade association for the nation's tire manufacturers, represents an industry in which product development has led to more durable and longer-lasting tires year after year. In the 1960s, 20,000 miles was considered good mileage for a set of tires. In the 1970s and 1980s, tire mileage commonly increased to the 30,000 and 40,000-mile range. Now there are tires that are serviceable to 60,000 and 80,000 miles of use. Indeed, there is a wide variety of tire designs and usages as illustrated by the breadth of UTQG grades and the wide range of applications on passenger cars, SUVs, pick-up trucks, RVs and vans of various sizes, including 15-passenger vans. Additionally, since service conditions vary widely (load, speed, inflation pressure, road hazard injury, etc.), accurately predicting the service life of any specific tire has not been possible. To date, the tire industry has no data that yields a specific maximum service life for all tires. In fact, drawing generalizations can be misleading.
Therefore, the Rubber Manufacturers Association is concerned that recent media reports regarding assertions by two U.S. automobile manufacturers that there is a correlation between chronological "tire age" and tire performance may mislead American motorists. In particular, both Ford Motor Co. and Daimler/Chrysler have issued statements advising consumers to replace tires, regardless of tread depth or service conditions, six years after their date of manufacture.
We want to be clear on the question of whether there is any relationship between "tire age" and tire safety performance. First, we note that "tire age" is not an appropriate term. The issue does not involve the time period from when a tire was manufactured, i.e., its age, but rather the tire's use on a vehicle, i.e., the tire's service life. Concerning tire service life, RMA and its member companies are not aware of any factual or scientific data that establish a relationship between tire service life and tire safety performance. RMA will attempt to obtain and evaluate the data upon which Ford relies in releasing its statement. In fact, the auto industry appears to be divided on this issue: It is our understanding that General Motors Corp., for example, has refrained from making a similar recommendation for its vehicle owners, stating: "The customer operating environment for the main aging factors varies greatly and that makes it difficult to select a specific age when tires should he replaced." We do not believe the public is well served if there is material disagreement on such an important issue.
As the regulatory agency charged with protecting consumers and advancing highway safety, NHTSA is well-suited to ensure that any message to consumers about the service life of a tire is based on sound science and is fully supported by data that can be validated by the Agency. In the absence of any such data, and until this issue is resolved, we would ask NHTSA to issue a consumer advisory on proper tire care. According to NHTSA statistics, under-inflated tires are a contributing factor in 660 fatalities and more than 33,000 injuries each year. Since tires are a critical safety component on every vehicle, a consumer advisory would help to advance awareness of proper tire care. This advisory could include much of the same information that the Agency is already distributing as part of the "What's Your PSI?" tire safety campaign. Further, the RMA is prepared to work with NHTSA in seeking scientific data to answer the question of whether tire service life alone has an effect on real-world tire safety performance.
Below, we discuss the factors that affect the service life of a tire and the fundamental question that must he addressed before well-considered action can he taken in connection with this issue. We have also submitted an electronic version of this letter to the above-captioned docket.
The Service Life Of A Tire Cannot Be Determined in Advance
Tires are designed and built to provide many thousands of miles of excellent service. For maximum benefit, tires must be maintained properly to avoid tire damage that may result in tire disablement. Thus, the serviceability of a tire over time is a function of the storage and service conditions (load, speed, inflation pressure, road hazard injury, etc.) to which a tire is subjected. Since service conditions vary widely, accurately predicting the serviceable life of any specific tire in chronological time is not possible with the data currently available to RMA. Vehicle manufacturers may also recommend, but cannot determine when a tire should be replaced based on their understanding of the vehicle application.
The Consumer Plays An Important Role In Tire Maintenance
The tire industry has long recognized the consumers' role in the regular care and maintenance of their tires. Tires should be removed from service for several reasons, including tread worn down to minimum depth, signs of damage (cuts, cracks, bulges, etc.) or signs of abuse (under-inflation, overloading, etc). That is why it is recommended to have tires, including spares, inspected regularly. A monthly maintenance inspection, for which the consumer is responsible, for proper inflation pressure and tread wear should be supplemented by recurring rotation, balancing and alignment services. This monthly inspection should occur whether or not the vehicle is equipped with a tire pressure monitoring system.
Additionally, the condition of a tire should be assessed regularly to determine if there are any tactile or visual signs of damage that make a replacement necessary.
Tire Storage Conditions Are Also Important
Tires should always he stored in a dry, cool, well-ventilated place. Consumers should avoid storing tires in areas that are exposed to wetness, extreme temperatures, direct sunlight, and/or other sources of ozone, such as electric motors. Tire manufacturers also recommend that a matching full-size spare tire (same size and type as other in-service tires) should he rotated into service as part of the regular rotation. When any such spare tire is placed into service, its inflation pressure should he checked immediately. With this practice, tires will wear evenly and will he replaced consistently. Consumers should also always consult the vehicle manufacturer's recommendation for the appropriate tire rotation pattern.
Other Conditions That May Require Tire Replacement
Even when following good tire storage and maintenance practices, it is not always possible to ensure that the tires do not have an internal condition that may render them to be unacceptable for continued service. Consumers should therefore not rely solely on the appearance of the tire. Consumers are strongly encouraged to be aware not only of their tires' visual condition but also of any change in dynamic performance such as increased air loss, noise or vibration, which could be an indicator that the tires should he immediately removed from service to prevent a tire failure. Also, the consumer should be the first to recognize a severe in-service impact to a tire and to ensure that the tire is inspected immediately thereafter.
The Fundamental Question That Must Be Addressed
As the above discussion illustrates, there are a number of factors that affect the service life of a tire. In our view, the fundamental question that NHTSA, the tire industry and vehicle manufacturers must address is whether there is any scientifically valid data that demonstrates a correlation between tire service life and real-world tire safety performance, and does such data, if available, lead to a reasonably identifiable maximum service life.
Without data to support such a correlation, there is a substantial risk that any policy, requirement, or recommendation to replace tires after a certain number of years will impose unnecessary costs on consumers, including the risk that consumers will rely on a so-called "tire expiration date" as a guarantee that the tire will perform for that period of time, regardless of the tire's mileage and other conditions that bear on the issue of tire replacenwnt as discussed above. Additional environmental impacts (i.e., an increase in the scrap tire generation rate per mile driven) and other societal costs should also be considered as part of any public policy developed in connection with this issue.
RMA is prepared to work with NHTSA to evaluate the data that Ford and others have cited as evidence of the need to advise consumers that their tires should be replaced after six years. Again, however, we emphasize the need to answer the fundamental question -- whether tire service life alone has an effect on real-world tire safety performance -- before the Agency settles on the appropriate course of action. Only by answering this question can NHTSA, the tire industry, the auto industry, and others concerned with highway safety be assured that consumers are given the right advice.
In the meantime, RMA recommends that NHTSA issue a consumer advisory regarding proper tire care (similar to the message contained in the Agency's ongoing "What’s Your PSI?" tire safety campaign) which outlines the factors that affect the service life of a tire as described above and includes the other demonstrable benefits of proper tire maintenance. RMA stands ready to work with the Agency and other interested parties in developing and conveying such messages.
Sincerely, Donald B. Shea
