Current Issue
Published on October 24, 2005

Tire aging bombshell: Curing an unsubstantiated problem could cause harm



AKRON (Oct. 24, 2005) — I want to address the world of tire safety and how certain aspects of the Transportation Recall Enhancement, Accountability and Documentation (TREAD) Act may be interacting with the real world of tire safety.

The TREAD Act may not achieve its intended safety-related purpose. It already may be activating the dreaded “Law of Unintended Consequences.”

For most people, buying or maintaining tires is not a happy event. Many consider it a major expense and an inconvenience that can be delayed or can be an annoying “dirty your knees” procedure.

An important aspect of tire safety always has been the affordability and easy accessibility of new replacement tires by size and performance ratings. Sets of new tires still can be purchased for less than the cost of designer sneakers. Despite these industry achievements, it is disturbingly common for tires of unknown service history and damage to find their way from yard sales, scrapped vehicles and junk piles onto vehicles.

The real world of tire durability is complex and includes this large marginal population. Perhaps even a larger questionable population is generated by new tires that have been exposed to a wide range of conditions that cause excessive deflection (distortion and internal heat generation), which accelerates oxidative and thermal degradation. (Notice the term “age” is not used.)

The 1 billion tires successfully running on U.S. roads (racking up about 3 trillion miles per year) attest to the safety and reliability of tires. Tire safety is affected by affordability. The conservative estimated net cost of the new Federal Motor Vehicle Safety Standard 139 by the Center for Regulatory Effectiveness is about $5 billion, which can be expected to be passed on to the consumer.

Even with its more demanding test requirements, the TREAD Act will not result in a massive reduction of unreliable tires on the road. It's probable the higher cost of tires will cause an increase in the population of marginal “end-of-service life” or damaged tires.

Tire aging is the current hot-button tire performance issue as the federal rulemaking process enters its final stages. Aging is not a proper description for the tire weakening processes. Aging limits cannot be all-inclusive and justified by perceived dangers. They require scientifically proven tire performance deficiencies caused by specific conditions—i.e., inflated vs. uninflated, static vs. dynamic, etc.

Oxidation is the proper chemical description for the tire weakening process. Most elastomers used in tires oxidize over time, but the rate and the degree are very dependent upon the chemistry of the materials, the tire usage history and the service environment.

Chronological age can be misleading since it doesn't address chemical kinetics variability within the materials and laminated structures. To use chronological age as the basis for relegating a tire to the scrap pile makes no chemical sense.

I would expect Department of Energy and Environmental Protection Agency people to take positions of interest since the scrapping of each good tire represents about eight wasted gallons of oil, as well as overburdened landfills being stressed with a non-biodegradable, combustible material.

To put a chronological age limit on tires that are properly stored for two to four years before application is not a scientifically proven necessity. This will certainly cause an economic and logistic disruption to a finely tuned, rapid response, international distribution system that is an important part of the tire safety equation.

Besides the consumer's having to absorb higher distribution cost burdens, the timely replacement of marginal tires also would become more inconvenient because of a more limited availability of the correct tires. Dealers would have to maintain low inventories to minimize the number of “older” tires in the store and the potential added costs of dated tire rejections by the customer. The economy of scale for tire makers also would be compromised with shorter production runs needed to maintain minimal inventories.

Consideration of alternatives to the proposed rulemaking that won't cause the collateral tire safety damage would include a more concentrated effort to make tire rotation (including the full size spare) an important safety responsibility assigned to the motorist.

Tires would wear out and be removed in a more predictable and uniform manner. I also suggest revisiting the proposal to raise the mandated 2/32 height of wear-out indicators. This would yield a variety of safety benefits besides giving more localized wear-out safety margins during the final months of a tire's service life.

Also, federally mandated placement of the wear-out indicators should be modified for radial tire wear patterns so as to be placed over the more vulnerable belt edge area where many over-deflection separations initiate.

High-purity nitrogen already is starting to make its evolutionary contribution to tire maintenance.

State-of-the-art, high-purity nitrogen inflation (more than 95 percent actually in the tire) is now prac-tical with new compact and economical generators that would complement already proven and critical tire maintenance procedures.

Nitrogen's slower permeability characteristics coupled with its bone-dry nature may partially ameliorate some field abuse conditions, including long term inflation maintenance neglect, improper repairs and certain types of tire pressure monitor malfunctions. Even though high purity nitrogen inflation is no guarantee of performance and will not undo the many forms of damage or abuse that can lead to tire failure, it offers a low-cost, risk-free and positive service opportunity that has now become commercially and technically practical.

More conversation and thought (and delay) is warranted before tire aging and dating standards become a mandated requirement. Science doesn't respond to legislative timetables or to special interest groups making the most noise. Common sense tells us there are easier, more meaningful, less disruptive, less complex and certainly, less costly things available to improve tire reliability.

We all want to make the roads safer. Let's keep things in perspective as we consider expensive, disruptive and possibly harmful rules and protocols.

Mr. Herzlich is a consultant and the technical editor of Rubber & Plastics News, a sister publication of Tire Business. He has 49 years of experience in tire technology.


Frequently Asked Questions

For any questions regarding your subscriptions or account, please click HERE.