ITEC 2004 Paper 23

55 YEARS OF RADIALIZATION

Jacques Bajer Tire Systems Engineering, Inc. Paper 23

ITEC 2004 Paper 23

Reprint only with permission of Rubber & Plastics News, published by Crain Communications, Inc.

T1~E SYSTEMS ENGJNEER1NG, iNC. 16825 Kercheval Ave. Grosse Pointe, M! 48230, U.S.A. Phone: 313/886-6860 Fax: 313/882-3173

Consultants and Designers in Road Tire Vehicle Systems Technology Raw Edge V-Belt and Radial Ply Tire Technology and Manufacturing Systems

PRESENTED AT THE INTERNATIONAL TIRE EXPOSITION & CONFERENCE SEPTEMBER 21-23, 2004 AKRON, OH

Thank you, _____ and good afternoon Ladies and Gentlemen.

Let’s see if I can sqi..iee.ze 55 years of radialization into 35 minutes. I shall start with a preamble, followed with the beginnings of radialization in Franceand the United States, and will continue with the situation today, and wrap it up with the future as I see it.

Because of the limited time allocated,, my speech is only about radial ply tires used on passenger cars, station wagcns., minivans, SUVs and light trucks~using passenger car type tires.

P REAMBLE

Revolutions, in the long run, seldom achieve the objectives of those initiating them. With the radial revolution, the objectives of the pioneers were lower tire operating temperatures and long life. However, over the years, and with the proliferation of tire types, sizes and aspect ratios, the basic product gradually became less and less revolutionary as far as long life is concerned. Keep in mind that long tire life, which means economics, was the primary promise of radialization.

The life of a tire manufactured at reasonable levels of precision and uniformity, and selected to operate on a vehicle at a given load, inflation pressure and deflection, depends on the degree of road surface abrasiveness, the type of terrain, the tire architecture, the tire tread design and compound used, the vehicle speed, the severity and frequency of vehicle straight—ahead,acceleration, deceleration and cornering operations, the vehicle design effects, the meteorological/climatic conditions and, last but not least, the road hazards and lèiiel of maintenance tires encounter in the process of providing vehicle functions. Needless to say that, if tires operated only straight ahead, with no camber,toe and longitudinal forces,tire life would be great. 55 YEARS OF RADIALIZATION

The evolution of the pneumatic tire, since Thomson invented it in 1845, has been directly linked to the development of cars and roads, to the correct matching of a given tire architecture and size to a particular vehicle,and, again, to the level of precision and uniformity by which tires are produced.

In view of concerns about.tire structural integrity, vehicle fuel consumption, roll-over, the use of limited stroke ultra—low section height tires, tire bead unseating, etc.., attention has been focused on large, heavy, highly powered rear wheel drive, front wheel drive and four wheel drive vehicles which operate at very high speed, at times fully loaded. At the end of the day, the tires must safely absorb all vehicle operational inputs, and in the process,remain smooth—running and in one piece, preferably for 50,000 miles or more. No tire pressure monitoring system, nor the use of high load reserve tires can be effective if, in the process of wearing their treads out, tires do not remain in one piece.

Another promise of radialization was lower tire rolling resistance, hence lower vehicle fuel consumption, and lower tire operating temperature. Up to a point, the benefits of such tire operational characteristics were achieved, but,in my view, not to the level of expectations originally anticipated, based on tire power wastage, rolling resistance and temperature values obtained from indoor tire testing machines. For example, a lower tire rolling resistance —2—

has more of an effect on reducing the fuel consumption of a light, rQasonably dimensioned and powered, streamlined vehicle,than on the type of vehicle I previously mentioned. On the other hand, the real World, non— steady operational nature of any ground vehicle has a negative effect on vehicle fuel consumption.

One of the many operational characteristics of pneumatic tires is the tire to road surface tangential force. This force increases rapidly as the vehicle propels itself straight ahead through the air and windage, particularly at speeds above 45-50 MPH, and when tire operating temperatures are low. Tires can indeed by structural] challenged when operating highly loaded and at excessively high temperatures and speed, but they can be equally challenged, dependinc upon conditions, when operating lightly loaded, at low temperatures and low speed. ~i~ie critical factor to keep in mind is tire deflectic

Very early on I learned, th’~t the radial ply tire basic structural discontinuities, where the stiff steel cord belt joins the flexible radial casing, required tire design application specific compounds capable of providing a high level of thermo—mechanical performance, high fatigue and aging properties, and considerably enhanced tire intercomponent bond strength in the chemico—physical sense, particularly within and between the tire steel cord belt plies —2—

and between the tire belt sub-assembly and the radial casing. All this, again, because of the promise of long tire life.

In time, the industry was able to respond to these challenges, particularly when, in 1969, the year of the cap ply, Pirelli became the first tire manufacturer to circumferentially apply rubberized nylon cords over their radial ply tire 2 steel cord belt plies, banding them securely to the tire rayon cord radial body.

The Pirelli CN36 became the first radial ply passenger car tire to incorporate this highly desirable, when well executed, tire design .fea~e, which significantly increased the tire structural endurance at the belt edge to radial body ply interface, and also resulted in improved vehicle steering characteristics over a wide range of operating conditions. Finally, the use of innerliners featuring a high level of tire inflation pressure retention was a major factor in improving the durability of tubeless radial ply tires.

1 Billion passenger car and light truck radial ply tires are operating daily in North America. This evolution is also taking place elsewhere in the

World, even though a significant portion of i remains to be radialized. —5—

BIRTH OF RADIALIZATION

Radialization started in France in 1946, right after World War 2, when a patent application for a radial belted tire architecture was filed by

Michelin in Paris. The final document was published in 1951. The innovative tire, named “X”, was first shown publically at the 1949 Paris Auto Show, and by 1953 was used on the equally innovative CITROEN 11 CV front wheel drive passenger car, which had been in production in France since 1934 and was wearing its front tires twice as fast as its rear tires, as all front wheel drive cars do. The “X” tires were black wall tube type, and of ~80 aspect ratio when fitted on a rim of width dimension representing 70% of the tire inflated section width. They used a highly siped tread design called “STOP”, introduced by Michelin, first in 1934 on a high section height bias ply tire, and lateron in 1937 on a then new, low section height bias ply tire named “PILOTE”, also of .80 in aspect ratio on a 70% rim. The stop tread, when used with the belted radial tire casing, was highly stabilized through the use of 3. high density steel cord tri—angulated belt plies, decoupling the tire belt/tread sub-assembly from the tire/wheel rim base through the tire flexible rayon cord radial body, In such form, the “X” tire maximized tread life for a given tread compound formulation, up to tripling it, as compared to the PILOTE bias ply tire previously used on the CITROEN 11 CV. —5—

In 1957, Ptrelli commercially introduced its version of a belted radial ply passenger car tire, using 4 rayon cord belt plies on a 2 ply rayon cord radial casing. Gradually,tire producers throuqhout the World slowly radialized, some through ratifying licensing agreements with Michelin and

Pirelli. Tire Engineering Performance Acceptance Criteria have indeed changed dramatically since radialization started in France right after World

War 2.

BADIALIZATION IN NORTH AMERICA

Radialization in North America, began at the replacement tire level when, in early 1966, Sears & Roebuck started selling Michelin radial passenger car tires of tube type construction, featuring narrow white sidewalls and .80 aspect ratio on a 70% rim. These tires, as compared to those first introduced in France in 1949, differed in tread design and belt construction. Of structural significance, they had a belt consisting of 2, low density steel cord belt plies rather than 3 high density steel cord belt plies originally used in the 1949 X tires. In addition, they featured a narrow textile cord low angle bias ply,positioned under the edges of the belt package and bridging the top radial body ply. This as.:’an effort to improve tire structural integrity. -12 —

The tires were warranted to last 40,000 miles under U.S. operating conditions. U.S. consumer reactions were mixed, due to vehicle ride harshness, boom, steering response and pull. You’ have to realize that, in

1966, the typical American body-on-frame car with its highly compliant suspension system aitid low pressure bias ply tires was the epitome of operating smoothness, comfort and low noise levels, and that when Sears started. to sell radial ply tires, “radial tuned” vehicles did not exist.

Radial tuning means desensitizing the vehicle from unwanted tire induced vehicle reactions, not an easy job, I can assure you, and this from hands—on tire/vehicle system development experience.

Prior to radialization, the then universally used bias ply tire with its absence of structural discontinuity, provided a more linear and slower development of cornering force over a wide range of vehicle operating conditions. From the NVH and ride standpoint, radial ply tires, when operating on a vehicle at: a given load and inflation pressure, deflected more, due to their much lower spring rates as compared to their equivalent size bias ply tires, giving the impression that a softer~:vehicle ride would result. Irt reality, the radial ply tire steel cord belt, under inflation pressure stresses, did not allow the tire to absorb sharp road bumps nearly as well as bias ply tires. Therefore, on untuned vehicles, -12 —

unacceptable ride harshness resulted. Also, on untuned vehicles, particularly those of unitized body construction, the typical radial ply tire resonant frequencies, when the tires rolled over these bumps and other types Of road surface irregularities, were disturbing to many consumers.

With vehicles of body—on—frame architecture, these disturbances were less severe, yet not attenuated enough to satisfy critical consumers. And even though some U.S. consumers appreciated the significantly longer tread life radial tires provided and put up with the negative aspects of the tire NVH and steering characteristics, vehicle development, upon radialization, required extensive road/tire/vehicle system tuning, in order to meet the expectations of the U.S. ‘Consumer who had become accustomed to the behaviour of vehicles equipped with bias ply tires.

In tubeless form, the use of radial ply tires resulted in an increased resistance to deflation when punctured within the tread zone, because of

.the ability of the tire tread belt sub-assembly and its adjacent radial casing and innerliner to retain puncturing objects, sealing them long enough for consumers to take corrective action. Punctures cannot be prevented,and remain the major problem confronting the pneumatic tire after nearly 160 years of existence. -12 —

According to my sources, 50 Million radial ply tires operating in North

America last year were repaired due to punctures, and many, with ample tread depth remaining, perished due to irrepairable punctures or poor repairs.

The use of radial ply tires also resulted in an increase in vehicle mobility, particularly when the tire dimensions were correctly proportioned, and the tire was well anchored to, and efficiently decoupled from, its rim.

This provided improved tire bead unseating performance, even when the tire operated significantly underinflated, which in 1964 meant down to 15 PSI from 24 PSI. In other words, with radial ply tires, runflatability performance was improved.

By 1970, following years of tire/vehicle system development, which included field testing, Ford began to use Michelin tubeless narrow white wall radial ply tires of .80 aspect ratio on 70% rims as standard original equipment on the 1970 Lincoln Continental MK3, a U.S. automotive industry first. This marked the real beginning of the radialization in North America at O.E.’

‘level, which in turn was to drive the North American tire replacement market fo~ radial ply tires on radial tuned vehicles. Consumer disenchantment with the poor life of 2ply G.E. bias tires,which wore their treads out in 20,000 miles or less, accelerated this trend. (Consumers had been accustomed to the performance of 4 ply rayon bias ply tires, which provided 25,000 miles of service, or more when upsizing, then a common practice.) -12 —

In the late 50’s/early 60’s, few tire producers outside Michelin, Pirelli,

Dunlop and Kieber were inclined to radialize, particularly U.S. tire producers, because of the technological know—how and enormous capital investment required. In reality, the radial revolution was in. the making, as by 1963 radial tires had become familiar to U.S. consumers who had experienced the longer life these tires provided on the vehicles imported to

North America. One such consumer was Andy Bush, a tire buyer at Sears & Roebuck in Chicago, who had discovered the extraordinary life of the

Michelin “X” replacement tires he had fitted to his Mercedes. Andy became the driving force behind the Sears radialization of the U.S. tire replacement market in 1966.

Of significance ..in the history of radialization was the elimination of passenger car and light truck tire retreading. Prior to radialization, 10,000 retreaders operated successfully in North

America, and 25% of all North American replacement bias ply tires for passenger car and light trucks were retreads, sold at 1/2 the price of new tires, hence providing a good value to Consumers, particularly to the economically challenged. Today about 800 retreaders remain, processing only medium/heavy duty truck, aircraft and off-the-road tire casings. Remember, retreadability of any tire casing is the best measure of the original tire quality, regardless if bias or radial. -12 — SITUATION TODAY

In contrast with the 50’s and 60’s when all passenger tires in North America were of bias ply construction and of the same aspect ratio, operating at the same inflation pressure (24 PSI), and no tire speed or other ratings existed, today’s radial passenger car tires come in a myriad of aspect ratios, speed, mileage, traction and temperature ratings, tread designs, some directional, cap ply treated or not, different tire and wheel sizes from front to rear axle positions, wheel sizes of 20” in bead diameter or more, such as last used in the 1920’s. Today, these large diameter wheels, up to 10” in rim width, are fitted with very low section height tires inflated at high pressures, such as, again, seen in the 1920’s. This situation raises not only issue~ of NVH, but also of more forces and shocks being transmitted to the vehicle components, starting with the wheel, of higher tire/wheel assembly rotating mass and rolling resistance, tire. dismounting and mounting difficulties, and, last but not least, higher prices at tire and wheel replacement time.

Today, a 2 tier tire type marketing situation has developeL One type is marketed as high performance, meaning high speed, high grip and faster, more direct steering response in exchange for limited life; the other, of standard performance and longer life. In Europe, the high performance type represents -12 —

70 to 75% of the market and is growing. In North America, the longer life tire represents 70% of the market, and is J decreasing. The questions are:

Is a more direct, fast steering response, higher speed tire really desirable and/or necessary, particularly under real World/low speed limits North

American vehicle operating conditions? Should the vehicle steering system, including tires, be more forgiving, particularly under crash avoidance steering manoeuvres? Isn’t the primary aspect of tire performance, from the consumer standpoint, long, smooth, reliable life, such as 50,000 miles or more? High performance tires do not provide such life. In fact, the field experience shows that, statistically,they provide 30,000 miles. This is hard to digest when considering that a set of 4 of these J,~t.±res pan retail:for up to $800 at replacement time.

If radial ply tires cannot fulfill the original promise of long life, hence providing an economic advantage to consumers, are we going to seethe industry having to.p.roduce twice as many tires as needed, resulting in scrap tire piles twice as high as they need to be, with the casing disposal problems this entails? And what about tire production demanding twice the amount of raw materials and energy, oil that is? If this low mileage trend continues, what was radialization all about? -12 —

Some will tell you that current trends are blessings in disguise, that low tire life means safety, because these tires are not likely to’ fatigue or be subjected to as many road hazards. But is such thinking conducive to progress? In the meantime, it remains to be seen if these trends persist, if long life tires will remain a selling point, and if consumers will accept radial ply tires providing bias ply tire mileage at radial ply tire prices.

In view of today’s tire/vehicle system operating conditions, the limits of currently used tire materials, tire/wheel/valve system designs and their manufacturing processes, the variety of topographical and climatic conditions and other hazards tires must endure throughout the World, the tire structural integrity issues encountered to date, and this regardless of root cause, the highly litigeous environment within which the industry must operate, it seems that there will be little to no option for the ordinary consumer, unless new types of tires, combining high performance and long life are soon developed and commercially available. -13 —

CLOSING THOUGHTS, WHERE DO WE GO FROM HERE?

The subject of tire manufacturing and p-rocesse’s required to produce precision, smooth—running, reliable long life tires, and this consistently, has not been as liberally covered or financed as far as technical publications go, as tire design and tire performance specifications.

Specifications and measurements are easier to obtain than solutions, and the disciplines of tire academic design have always been difficult to blend with the realities of tire manufacturing, and this so often to the dismay of tire designers.

The North American small tire market in 2003 required a production of about

250 Million tires, each consisting of 20 components, 10 different compounds, each compound requiring a multitude of different ingredients, all to be precisely weighed, metered and mixed into compounds. that must then be converted into precise tire components, which in turn need to be precisely assembled and cured into ready-to-use tires. Producing radial ply tires that fully satisfy consumers is not for the faint of heart.

The tire industry to date has served the public relatively awell. Again, 1

Billion tires operate daily in North America. Some quality guru wouldask: were they all produced at 6 sigma? With the tire and tire/vehicle system validation means at our disposal today, —14 —

this can be determined. At the end of the day, progress must prevail, jobs and economic well—being depend on it. The lessons learned from 55 years of radialization are the same as those I. learned by John F. Pur.dy, the great

Goodyear tire mathematician, years ago and before radialization begun:

“Tires must be designed, prd.ducedand applied based on the stresses, strains, temperatures and the many operational characteristics they must endure in the process of providing vehicle functions”. Of even greater importance, once a tire has been validated for consumer usage, the manufacturing process by which such tire is mass—produced must be conducive to repetitively high precision and uniformity throughout.

So, what should the tires of the future provide? In my view, they should be manufactured at superior precision and uniformity levels, and be structurally more robust, hence providing smooth, r~liab1e long life. They should also provide improved bead to rim retention (if by then tires ate still separate from their rims). The tires of the future should also be more resistant to punctures and deflations,and should eliminate tire related vehicle steering pull and its possible detrimental effect on tire life and abnormal tread wear. —15 —

Furthermore, the tires of the future should be easier to dismount when worn out or in need of repair, and easier to mount when repaired or replaced.

Finally, nitrogen inflation should be used.

All this represents major engineering based undertakings, requiring new tire, wheel, perhaps even valve design, new tire validation testing procedures, as well as new tire manufacturing and servicing processes.

The results should be Ibetter tires, performing more smoothly, more consistently and much longer, thereby reducing the number of tire related vehicle accidents, regardless of cause, as well as the amount of debris laying on our roads today. A recent Federal Highway Administration report indicates that road debris causes 25,000 wrecks a year in the U.S., with tire treads and

.stéel,cord belt fragments among the five most common items found.

But back to the future.

To reach the goals I previously mentioned, necessitates a united and well- guided technologically based effort, and a recognition from vehicle producers that tires are vital components of vehicles and therefore should be treated accordingly. —16 —

— 17 —

What will it take to enter a new wave of tire technological progress, such as when 55 years ago the radia] helt~d tir~ was first commercially introduced? Let me quote Albert Einstein, who said: “The significant problems we face cannot be solved at the same level of thinking we were at when we created them”. End of quote. Consequently, and in view of today’s much higher~ competitive nature of the automotive business, we must not relax our endeavour toward a constant objective, that of giving the consumer from which our livelihood depends, all the benefits that can be derived from technological progress.