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From radialization to the TPMS: The two technologies are becoming intertwined. And the evolution continues, according to an industry icon

Jacques Bajer
Posted on October 1, 2007
Jacques Bajer, president of Tire Systems Engineering Inc., and Peter Hall, systems engineer for Nira Dynamics AB.
Jacques Bajer, president of Tire Systems Engineering Inc., and Peter Hall, systems engineer for Nira Dynamics AB.

Jacques Bajer, president of Tire Systems Engineering Inc., is uniquely qualified to write about the radialization of the domestic automotive industry, because he was the man most responsible for its implementation!

He also has been a participant, sometimes as an observer, in the development of the tire pressure monitoring system (TPMS) for nearly 40 years. That includes attending the Intelligent Tire Technology conference on behalf of Modern Tire Dealer in May (some of his thoughts on the conference follow).

For his contributions to the tire and automotive industries, he was elected to the Tire Industry Association Hall of Fame in 2006.

In addition to MTD, he has written technical papers for the Society of Automotive Engineers (SAE), the Tire Society, the International Tire Exhibition and Conference, and the former American Retreaders Association.

Bajer cites the following as helpful references for his article: data from his company’s archives, which includes some of his work at the Ford Motor Co. from 1955-1970; and “The Radial Revolution” by Tim Moran, published in the spring 2001 issue of American Heritage of Invention & Technology magazine.

Years ago, when I first became interested in tires, and particularly in “road/tire/vehicle/driver system interactions” while working at Ford Motor Co. back in bias-ply tire days, one thing in addition to tire manufacturing precision and uniformity was in dire need of improvement: tire life.

This is what our safety, ecology, fuel economy and value-oriented inspiring leader, Robert McNamara pointed out. (McNamara is the former president of Ford and was U.S. Secretary of Defense from 1961-1968.)

Keep in mind that in the 1950s, a set of four 7.50xl4 four-ply rayon tubeless whitewall bias tires was capable, at best, of providing 24,000 miles of service. And the two-ply version of the early 1960s provided even less.

Also, these bias-ply tires had a rolling resistance 25% higher than the radial-ply tires Michelin Groupe had been producing in France since 1949. This meant higher vehicle fuel consumption. But in the 1950s, who cared, at 23 cents a gallon for regular gasoline?

Conservation was never an issue, although, under Mr. McNamara, it had been discussed.

My boss at Ford, Harold Johnson, who always provided me with the freedom and flexibility required for developing innovative practical solutions to our product development problems, one day in the late 1950s asked me, “What can we do to increase tire life to 50,000 miles without increasing tire size?”

Without hesitation, I responded that this could only be achieved with steel cord-belted radial-ply tires, but that at the moment this new type of tire was only produced by Michelin in France and in tube-type form. So, for years nothing happened. But due to a variety of circumstances, I finally got a radial-ply tire program going at Ford, and the rest is history.

Looking back, I believe that I happened to be at the right place at the right time, and that destiny, no doubt, had a lot to do with it.

What does this have to do with tire pressure monitoring systems, you might ask. Answer: more than you may think.

Birth of TPMS/U.S. radialization

Applying radial-ply tires to American cars was technologically challenging and required ingenuity and perseverance. Ford was the first American car producer to provide radial tires as 100% standard original equipment for its 1970 Lincoln Continental MK3. Historically, this was a very significant U.S. automotive industry event.

This effort required what I then called “road/tire/vehicle system tuning” in order to meet the expectations of American consumers who were accustomed to the excellent operating smoothness and handling characteristics typical of their four-ply, bias tire-equipped American cars.

It also became evident to me at the time, following comprehensive tire testing, that due to their basic architecture, steel cord-belted radial passenger car tires, although correctly inflated and loaded, exhibited higher stress/strain and thermal concentration points throughout their cross-sectional structures and looked significantly under-inflated compared to their equivalent size bias-ply tires.

These points were outlined to Francois Michelin who, in 1968, visited us in Dearborn, Mich., in conjunction with the Ford radialization program. He suggested that Ford develop a low tire pressure warning system, today called TPMS. This was the first time I ever heard about such a requirement, although a few years earlier we studied the possibility of having a central tire inflation system on one of our vehicles.

I started to think about how a low tire pressure warning system could be implemented, but never passed the thinking and sketching stages, for in my mind all that was needed was a simple manual tire pressure gauge.

The Michelin tires, to Akron’s dismay, were eventually released for production for the 1970 Lincoln Continental MK3 without a low tire pressure warning system. These radial-ply tires were of 80 aspect ratio, steel cord belted, tubeless whitewall construction, recommended to operate at an inflation pressure of 24 psi cold (at the prevailing ambient temperature).

Since then, many have tried to develop low tire pressure warning systems, but so far with mixed results.

Historically, tires have been extremely reliable, requiring little consumer attention or frequent inflation pressure corrections. Nevertheless, tire deflations due to punctures, the nemesis of all pneumatic tires, are still with us today.

Now, 40 years later, I am witnessing a U.S. government-based/mandated revival of the low tire pressure warning system, although by 1987, Chevrolet had already installed a direct-type TPMS previously developed by Clevite Industries Inc., later on Epic Technologies LLC, both of Milan, Ohio, for its Corvette model.

The original system was wireless and battery-less, using a piezoelectric power source, with the sensors strapped to the wheel rim wells (in order not to compromise the function of the tire valve). At the same time, Dunlop Tyres UK Ltd. in England was working on another approach to tire deflation warning, based on the measurements of wheel speed change as a function of tire inflation pressure losses (i.e., an indirect-type TPMS), and obtained a U.S. patent.

By 1994, Ford started to install the Epic direct system with lithium battery-powered sensors on the Lincoln Continental, in conjunction with the Michelin run-flat tires of the self-supporting type. However, the package was discontinued after only a few years, due to a lack of demand for the combination run-flat tire/TPMS, and also due to TPMS/tire field problems similar to those encountered today.

Of course, this was in pre-TREAD (Transportation Recall Enhancement, Accountability and Documentation) Act and FMVSS 138 days. It took the relatively recent Firestone tire/Ford Explorer rollover problems consumers experienced over a period of years for Congress, in the year 2000, to enact the TREAD Act and mandate the use of tire pressure monitoring systems of either the direct or indirect type.

I would like to add that for the government to mandate the use of new automotive systems and/or standards is one thing, but making them work to full consumer satisfaction is quite another. For if the government insists on a specific date by which, in this case, TPMS must be installed on all vehicles, the system may not be fully developed and ready for such consumer mass-usage, as a result of which we might be facing another round of problems.

Today, there are no systems on board vehicles capable of providing the driver with a warning of potential tire belt/tread detachments, and tire dealers, by just examining tires at, for example, rotation time, have no way of knowing if, internally, the tires are still in one piece.

Intelligent tire conference

While attending the second Intelligent Tire Technology conference in Dearborn earlier this year, I could not help witnessing a state of affairs similar to the one I mentioned above.

Please keep in mind that neither Congress nor NHTSA has a clear vision of what it takes to design, develop, mass-produce and apply reliable, economical, long-life automotive systems.

This would require a tremendously knowledgeable staff.

The government’s role should be to more closely work with the manufacturers, while keeping in clear focus what the consumers’ real needs are, and not forgetting the economic aspect of any government-mandated systems: affordability.

Government-mandated systems can be a two-sided sword. The experience, to date, clearly indicates that, without government intervention, many safety systems, for example, would not be on vehicles today.

Direct TPMS

At this point, the direct TPMS dominates the U.S. market, but in my opinion does not adequately fulfill Congress’ or NHTSA’s intents, nor does it meet consumers’ real world requirements.

First, ironically, the technology is still not fully developed or standardized, even after all these years. Second, current direct-type TPMS are electronically and mechanically cumbersome. Third, their installation, settings and maintenance are unnecessarily complicated and not intuitive -- in other words, not dealer or user-friendly. Also, they can malfunction while in service, and, with the tire valve stem-connected version, the sensors can compromise the function of the valve stems which, historically, have proven to be one of the most reliable vehicle components.

At the conference, it also was mentioned that servicing direct-type TPMS was an inconvenient and expensive proposition for consumers, from the first vehicle owner on down. The tire dealers currently also are negatively affected and sometimes have to purchase TPMS replacement parts from car dealers, which now also are tire dealers, hence competitors.

Emerging also are problems with logistics because of the high variety of systems on the market, their varying setting procedures required, necessitating extensive tire dealer personnel training and inventory, thus subjecting the consumer to additional vehicle operating expenses.

So, the question is: Can a practical, simple, more reliable, intuitive, standardized dealer and user-friendly economical TPMS be developed and commercially implemented? If so, how long will it take? In the meantime, should FMVSS 138 be rescinded until such a system becomes available? And is the U.S. government aware of the current messy situation?

Indirect TPMS

The original 80 aspect ratio tube-type, steel cord-belted radial passenger car tire exhibited a constant fixed length loaded tire dynamic rolling circumference tread, regardless of the amount of tire inflation pressure. This was in contrast with the then universally used four-ply, tube-type bias passenger car tire.

Each wheel fitted with these early radial ply tires rotated at the same speed, regardless of the amount of tire inflation pressure. This was due to the tire belt design, which consisted of three high density steel cord belt plies coupled to the tire’s two-ply, 90 degree radial body.

In 1956, Michelin simplified the tire by using only two (instead of three) steel cord belt plies, and of lower density, but still coupled to the tire’s two-ply 90 degree radial body. This change lightened the tire and made it less costly. Michelin also changed the tire aspect ratio from 80 to 78.

From these tire design changes, some aspects of the radial tire performance also changed, among them that the tire no longer operated at a constant fixed length loaded dynamic rolling circumference tread as a function of change in tire inflation pressure, hence acting somewhat like a bias-ply tire. This observation would eventually be the root of the indirect TPMS operating principle.

Today, for the indirect TPMS to perform to consumer expectations, the measurement of the change in tire dynamic rolling circumference, currently performed with the use of the vehicle anti-lock brake digital pulse generator, must be augmented by the use of other vehicle sub-system inputs, such as traction and stability control, which fortunately are now available on most vehicles. The indirect TPMS also must take into consideration all real world road/tire/vehicle system operational characteristics and their variables, sort out false alarms, and include replacement tires.

All this requires a monumental amount of tire/vehicle system development work, but with patience, dedication, know-how and the powerful means of computations, measurements and analysis at the disposal of development engineers today, it can be done.

So, with the indirect TPMS currently under development, there is hope for simplification and significant cost reduction for the benefit of all -- consumer, tire dealer and car dealer. And since the indirect TPMS, to perform efficiently, depends on inputs of other vehicle safety systems such as antilock brakes, traction and stability controls, etc., its adoption could make a significant improvement in overall vehicle safety at minimal cost.

Radials and direct and indirect TPMS

As mentioned earlier, punctures are the nemesis of pneumatic tires. It is typical of tubeless steel cord-belted radial-ply tires to lose pressure very slowly when punctured within their tread zone where most punctures occur. Such slow deflation is one of the many advantages offered by this type of tire, and this is why most people only notice that they have a flat tire when their vehicle has been parked for a relatively long period of time,

It is the purpose of any TPMS to warn the consumer, while driving, that one or more of his tires has lost air, so that corrective action can be taken as soon as possible. Some consumers would probably like to have their tire pressures displayed constantly while driving, just as their vehicle speed is constantly displayed, while others would like their tire pressure displayed “on demand.”

However, they all have one thing in common: They want to know that they are operating safely, and that their tire/wheel/valve systems are retaining their inflation pressure without frequent intervention. Most tires, wheels and valves today do just that, and recent tire inner liner development will improve on this aspect of tire performance.

The future

Tires hopefully will continue to be used as sensors, and they sooner or later will be able to warn the driver or dealer of deteriorating tire operating conditions such as smoothness, structural integrity and skid resistance before a catastrophic situation develops. In the process, the added value of tires will increase.

Finally, keep in mind that to safely provide all required vehicle functions, and there are many, tires must operate smoothly and remain in one piece until replacement time. When all the systems mentioned in this article become part of the overall vehicle/tire system package as standard original equipment for all types of vehicles and tires, the economies-of-scale derived from mass production will minimize the cost/price of such a package.

Tires are major components of vehicle safety and should be treated accordingly. They should not be treated as mere commodities.

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