An overview of tire technology.

There is no doubt that the mobilization of our society today can be traced back to the development and refinement of the wheel. Through history, the available technology of the era provided innovations that allowed the wheel to progress from solid stone to a spoked wooden wheel that was eventually covered with an iron ring.

In 1839, Charles Goodyear discovered vulcanization, the process of applying sulfur and heat to robber to stabilize its physical properties, and thus created a number of new possibilities and uses for rubber based materials. In 1845, a Scotsman by the name of Robert Thomson pushed the innovation envelope further by covering a wooden wheel with an elastomeric tube inflated with air. This initial idea never caught on until 1888, when John Dunlop further refined Thomson's concept by developing the first pneumatic tire (ref. 1). His objective was to replace the solid robber tires on his son's tricycle to provide a smoother ride.

From here, the 1900s brought a number of technological advancements in tires, primarily to keep up with the growing automotive industry and developing infrastructure. A few of the notable advancements include:

* the development of the tire bead which lead to the detachable "clincher" tire - wheel combination;

* the evolution of different carcass reinforcing materials from cotton to polyester to supply strength and dimensional stability to the tire;

* the discovery of carbon black's use in reinforcing robber compounds;

* the replacement of the innertube with the development of the "tubeless" tire;

* the progression from bias ply carcass design to radial ply carcass design (Att. 1);

* and finally, to today's innovations that allow a tire to travel a limited distance at reduced or zero air pressure i.e. the run-flat tire.

Most will agree that technology has driven all aspects of the transportation industry to the highly competitive level it is today. Advances in materials science and information processing have provided new tools for the design scientists and engineers to generate and evaluate new ideas at a faster and faster pace. The tire industry is no exception. As we evolved from drawing tables to CAD stations to interactive and predictive finite element models, virtual tire design has now become a reality. We are able to design and manufacture tires that deliver superior value to the user faster than ever before. Tires today offer reliable service, superior traction and handling in most types of weather conditions, smooth and quiet ride on most types of road surfaces, and they can last upwards of 120,000 kilometers. All of these benefits are delivered to the customer at a price similar to that of a good pair of running shoes.

Tire basics

Before we get too far along in our tire discussion, we should take the time to review a few basic terms and concepts. A tire can be viewed as a pneumatic, load carrying toroid that is a complex composite structure that behaves in a non-linear fashion. The tire's purpose is to provide driving and braking torque, cornering forces, and dampening characteristics to propel and control a vehicle in the direction of travel desired by the vehicle operator. The following discussion carries these ideas into six primary tire functions (ref. 2):

* The tire transmits forces from the engine's power output to move the vehicle as well as to the braking forces needed to stop. How well these forces are transmitted depends on the quality of those few square centimeters of tire in contact with the ground - this interface is referred to as the "footprint." It is interesting to note that the contact area of each tire on your car is about the size of a postcard, and it's through this small area that all driver/vehicle control inputs travel.

* The tire steers the vehicle with precision. The vehicle's ability to travel in a straight path depends on the tire's ability to maintain its course. The tire has to absorb transverse forces without deviating from the vehicle's trajectory. Generally speaking, each vehicle has a particular recommended inflation pressure for the tires of each axle. By using the recommended inflation pressure in the front and rear tires, an optimum driving precision can be obtained. Note that the proper inflation pressure for the tires on your vehicle can be found on the vehicle information placard placed on the doorjamb or in the glove box of the vehicle - it is not the air pressure molded on the sidewall of the tire!

* The tire supports the vehicle when it is stationary and when it is in motion. The tire must accommodate considerable load transfer during acceleration or braking. A passenger car tire will likely support and carry over 50 times its own weight.

* The tire rolls the vehicle evenly and smoothly to provide greater driving pleasure and controlled fuel consumption.

* The tire's enveloping characteristics absorb bumps in the road to make life more comfortable for the driver and passengers, as well as helping the vehicle to last longer. Flexibility, especially in the vertical direction, is the main characteristic of the tire that helps dampen the bumps. The great elasticity of the air contained in the tire enables it to withstand successive deformations caused by obstacles and uneven road surfaces. Once again, the correct inflation pressure is necessary to ensure a reasonable degree of comfort while maintaining the correct steering response.

* The tire lasts, i.e., continues to deliver performance for millions of revolutions of the wheel. The longevity and wear pattern of the tread depends on how the tire is used (load, speed, road surface, condition of the vehicle, driving style, etc.), but especially on proper contact with the ground. Again, tire inflation pressure plays a major role as it affects the size and shape of the contact area as well as the distribution of forces across the footprint of the tire in contact with the ground.

From this brief discussion, one thing should be certain: the tire needs proper inflation air pressure in order to function correctly and deliver the service life expected. It is the inflation pressure in the "pneumatic" tire that controls the deflection, spring rate, and consequent heat build up tendencies of the tire. The tire's inflation pressure therefore, must be checked regularly. This is because the tire's inflation air escapes molecule by molecule through the (albeit low) natural porosity of the rubber as well as through accidental causes such as leaks in the valve or at the rim, or punctures to the tire. Regular checks of your vehicle's tire pressure can help you avoid a lot of problems.

Discussion of tire components

Now that we know what the tire does for our vehicles, let's briefly introduce the key components that make up a tire.

The typical passenger radial tire has twelve to sixteen basic components, each composed of a blend of twelve to twenty ingredients such as natural rubber, synthetic polymers, carbon black, curatives, antidegradents, reinforcing fibers and processing oils. How these individual components are formulated, shaped, joined together and vulcanized into a tire represent the technology overview we are discussing.

The composite nature of today's radial tire can be seen in figure 1:

* Tread - is an all rubber part extruded into a specific profile. It can be a blend of natural rubber, polyisoprene, styrene-butadiene or polybutadiene, depending on the particular performance levels the tire engineer is targeting. Also, it will be reinforced with different grades of carbon black and perhaps silica for particular wear or traction properties. The primary purpose of the tread is to provide traction and resist abrasion wear.

* Base - is a rubber part attached to or extruded to the underside of tread. Its purpose is to reduce heat build-up in tread area, particularly in the shoulder and buttress. It also serves to increase adhesion between the tread and top belt component.

* Belts - are generally brass-coated steel wires that are covered with a high adhesion, high tear strength rubber compound. Belts can also be of aramid or fiberglass. The belt serves to distribute tire load and maintain radial tire shape and profile. The belts also serve to strengthen and stiffen the tread region to reduce tread element movement, thus providing good impact resistance, steering and treadwear characteristics.

* Sidewall - is an all rubber component extruded into a specific profile. It is compounded to provide resistance to ozone and weather effects as well as abrasion as it serves to protect the body plies. The compound must maintain flexibility without cracking when subjected to severe distortion over a range of temperature conditions.

* Body or carcass plies - rubber coated polyester, nylon, rayon, aramid or steel cords. The component provides the necessary carcass strength to contain the air volume needed to support the load.

* Innerliner - is an all rubber sheet, generally very high in halobutyl content. This component restricts the air molecules from traveling into the tire carcass.

* Bead filler - is an all rubber, extruded wedge of relatively high hardness. Its purpose is to stiffen the lower sidewall to aid in vehicle handling.

* Bead bundle - consists of a bundle of rubber coated, high tensile wires formed in a circular shape. This component is the foundation of the tire as it allows the tire to fit correctly on the rim. It provides strength to endure stresses from braking, acceleration, cornering, etc.

* Chafer/rim cushion - can be a rubber coated, square woven fabric or an all rubber extruded component. It serves to protect against chafing between the tire and rim in the flange area. It also strengthens the bead toe area to reduce the possibility of toe tear during tire mounting on the rim.

* Veneer - is a thin rubber skin covering the white stock of the sidewall. It protects the white sidewall stock from discoloration, weathering and abrasion.

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As you can imagine, changing the physical properties, shape, and strength of the various tire components will alter the performance attributes of the tire - understanding and being able to predict and optimize the outcomes of the various combinations is the real crux of tire technology.

Components of tire technology

As you know, there are numerous types of tires in the marketplace, all designed to provide a specific set of performance attributes for a specific target market. For instance, we have standard passenger car tires, tires designed for sport utility vehicles, tires designed for commercial trucks, on-off road trucks, agricultural vehicles and aircraft applications, to name a few.

Each of these can be further divided. Within the passenger car tire arena we have summer designs, winter designs and all season designs - depending primarily on the attributes of the tread pattern and physical properties of the tread rubber stock. Within each of these categories we can have typical use breadline sedan tires or high performance tires that provide superior levels of grip to the roadway and are able to withstand the forces of high-speed operation up to 300 kph.

For the most part, a tire represents a series of design tradeoffs that the engineer makes in order to achieve the performance requirements for the specific tire market being addressed. For example, to develop a superior winter traction tire, the engineer may have to design a tread pattern that is fairly aggressive with deep lugs to provide additional bite in soft packed snow. The product may also require a special tread compound that remains flexible at low ambient temperatures to aid in traction. The compromise here may very well be a tire design that has a noise level that is relatively louder when it is operated on the normal highway and due to the "softer" tread, it may very well exhibit a faster rate of wear.

A number of technology modules must be available to the tire scientist in order to minimize the tradeoffs and optimize the tire's specific performance. A few of the required technology modules can be grouped as follows.

Inflated shape and footprint characteristics

These are controlled largely by the shape of the tire mold and physical properties of the tire components. Dimensional standards exist that guide the engineer in determining the overall envelope dimension of the tire. Beyond that, he is free to determine the various radii and shape of the tread, sidewall, and bead regions. These characteristics are now frequently calculated and predicted using finite element modeling techniques such that the engineer can generate an inflated, unloaded and loaded view of the tire and footprint in a matter of minutes. This iteration used to take several months of trial and error design time by using actual prototype tires to verify the initial calculations.

Carcass and belt durability

These are often the next consideration for the engineer. The tire must withstand the millions of strain cycles it encounters during its service life. Once again, through advances in high speed computing and finite element modeling techniques, the engineer can gain an idea of the internal stress and heat generation tendency of a number of particular tire shapes and constructions in a matter of days. He is now able to weed out relatively poor profile/material combinations quickly and complete validation testing on candidates much more likely to succeed in achieving the performance targets. In the past, tools of this type were not available to the design engineer - who again had to rely on verifying the idea through procurement and testing of numerous prototype tires - a cycle that could take upwards of a year to complete.

Braking and handling

On dry, wet and winter surfaces, braking and handling must also be considered. The technologies required for these will generally relate to the pattern design of the tread, the physical properties of the tread compound over a range of temperatures and the stiffness of the belt and lower sidewall region. Today, these performance attributes are generally measured by means of on vehicle tests conducted at various proving grounds. Advances in vehicle handling simulation and computer modeling are being made and it is likely that future models will be developed to predict the tire's ability on various surfaces under various dynamic conditions.

Noise, vibration and harshness

These relate to the tire's ability to generate low levels of air-born noise due to rotational impact, provide smooth vibration-free service over a range of speeds, and dampen road irregularities to maintain a comfortable driving environment. Primary contributors relating to NVH properties are carcass stiffness, profile shape, tread dampening ability and manufacturing consistency.

Rolling resistance 

This is a measure of the hysteretic properties of the tire. A low rolling resistance tire will roll easier and require less fuel consumption. This is a key performance attribute for tire manufacturers who supply fires directly to vehicle manufacturers that must meet certain fuel consumption requirements (CAFE). Once again, the role of compound properties, inflation pressure and tire shape together play a major role in the level of rolling resistance generated.

Treadwear

Overall tread life is an area of prime concern in that the North American tire customer generally equates maximum value to a high number of kilometers of service. As you would expect, treadwear is directly related to the compound properties of the tread, the stability of the individual tread elements as they roll through the footprint, and overall stiffness of the belt region. The historic tradeoff between high mileage and lower wet and winter traction has been an area of study and of recent technology advancement. Many tire manufactures are now incorporating a blend of carbon black and silica reinforcement in their tread compounds to minimize the traditional tradeoff between traction and wear. This is a very good example of a materials change directly increasing the performance envelope of tire technology.

Validation of tire technology

The impact and effectiveness of the various tire technologies are proven to the tire scientist in the real world by means of a number of indoor lab tests and outdoor, on vehicle tests. We have mentioned a number of them already but to reiterate:

* Indoor tests - are used to check dimensions, footprint shape, noise, rolling resistance, impact resistance, force and moment properties and carcass durability. Durability can take the form of high speed testing where the load on the tire is constant and the speed is increased in predetermined intervals or it can be an endurance test where speed is constant and load is increased. Test engineers can use a variety of test equipment that induce camber angles into the footprint as well as steer rates - all in the attempt to determine and understand how the tire reacts to various forces. By understanding tire behavior in the controlled lab environment, better simulation models can be developed that allow the engineer to speed the development process.

* Outdoor tests - or on vehicle tests - represent some of the final hurdles during the new product development. As discussed, braking and handling tests are conducted on a variety of surfaces to characterize the tire performance in a number of environments. Ride quality is evaluated by driving over a number of different road surfaces to determine tire characteristic behavior. In addition high mileage treadwear and carcass durability tests are conducted to help ensure the tire will meet the customers' expectations. As you can imagine, these types of tests often take the most time and involve the greatest expense to complete but thus far, are the real validation of tire technology.

Tire technology - future

The topic of advanced tire modeling was mentioned several times. This has been and will likely continue to be a key area of development activity for all companies in our industry. With product life cycles getting shorter and market competition increasing, it will be critical that new products are brought to market faster, that their performance attributes be better than their predecessors, and that it all is accomplished at a lower cost than ever before (ref. 3). This is a tall order, but we will be counting on technology and our competitive nature to carry us through.

The development of advanced tire models to predict tire performance along with high speed computer processing will allow tire scientists and engineers in the near future the ability to get creative and complete more and better virtual tire developments. All with the key goal of using technology to get a better product to market, quicker.

Overview of tire technology - manufacturing

In looking at changes in tire manufacturing over the past 30 years, one would likely say the changes have been evolutionary rather than revolutionary. The processes of mixing, calendering, extruding, building and curing, still remain as discreet areas for most production facilities. However, the equipment in those areas is not the same as it used to be.

In the past couple of years, information has been disclosed on manufacturing methods that smear some of the traditional boundaries. Processes like Michelin's C3M and Pirelli's MIRS could change the way that we make tires. Before we go deeper into these new approaches, we will look at conventional equipment evolution.

Mixing

"Quality starts in mixing" is a quote that has been uttered numerous times. Many of the improvements in mixing have been to improve throughput without sacrificing mix consistency. The internal mixer continues to be the most common process used in tire operations.

While the mixing body has not changed significantly through the years, material handling, rotor design and control systems have. Years ago, one would have found many materials moved, weighed and loaded by hand. Carbon black handling has progressed from bags to mechanical handling systems to pneumatic systems. The latest installations have dust collection systems that enable mixing areas to remain as clean as office areas.

Rotor designs have progressed from 2-wing to 4-wing to 6-wing. Rotors in the tire industry have typically been tangential. This allowed for polymer ingestion and faster temperature build up early in the mix cycle, which resulted in higher throughput. Recent trends have been toward intermeshing rotors. The intermeshing rotors can better process temperature sensitive stocks as well as improve mix consistency. Examples can be seen in figure 2. Hydraulic rams have replaced pneumatic rams, which have also helped to improve mixed stock quality.

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The largest change in the mixing area has been in mixer controls. In the past, the mix cycle was controlled by time and temperature. Rotors turned at set speeds. Cooling was done with cold water with an on/off cycle. The latest mixers are using time, temperature and power, both instantaneous and accumulative, to determine the mix cycle. Speed of the rotors is varied through the cycle. Hydrotherms control the mixer part temperatures within a few degrees. Ram pressures change within the cycle. Pulling things all together, closed loop mixer control is currently available.

Extrusion

In moving forward in the tire manufacturing process, we can see that extrusion lines have changed by similar degrees. In years past, hot feed extruders were fed from mills to break down the stock. Most extruders were designed with a head that allowed for the profiling of a single stock. New technology and developments in extruder head design led to multi-stock extrusions.

Many of the extrusion lines in tire factories today are cold feed pin barrel designs. The cold feed operation uses less floor space than having a series of mills. The pins in the barrel allow for more shear points, to break down stock, providing a more homogeneous output than a smooth-walled cold feed extruder.

Some of the biggest changes in the extrusion lines have come in the head configurations.

The head transports the stock from the end of the barrel to a profiled die. The key being taking the round shape with an uneven pressure profile, and transforming it to a laminar even flowing extrudate. When using a single stock, the geometry is fairly straightforward. Flat plate dies are commonly used to produce the profiled shape.

Historically craftsmen would cut, grind, file and braze on dies to produce the desired final extrudate profile. Today's technology allows us to model stock flow through an extruder. Coupling this with today's machining technology allows the extrusion engineer the ability to produce a desired extruded profile with only one cut of metal.

When multiple stocks are involved, the geometries are much more complex. In three stock (triplex), and four stock (quadraplex) extruder lines, the extruders commonly are stacked in a vertical arrangement, with the ends of the extruders converging at the head. These layouts can be seen in figure 3. The head will then have multiple flow channel inserts to direct the stock to the desired location on the profile. A final die will again be used to give the exact dimensions required for quality tire production.

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Measurement tools to verify extrusion quality have advanced in the past few years. Not long ago the key instruments used to check an extrusion were a steel rule and a caliper. While these met the requirements at the time, the resolution was not good, and the dependency on the operator was great. Recent tools include line scanners to measure width in real time operation. Laser profile measurement systems allow fine resolution and minimize the operator error. An example of a laser profiled tread can be seen in figure 4.

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On the downstream side of an extrusion line, the products used to be wound up on small diameter reels or placed in a tread book for storage and transportation to the tire building area. These have been replaced with high capacity carts that are capable of building a few hundred tires. Where treads are still cut to length at the extruder, automatic booking has been implemented to eliminate deforming the tread.

Calendering

In looking at innerliner calendering, three and four roll calenders are still being used, much the same as 30 years ago. Upgrades in cooling and controls are the largest changes to those systems. The current state of the art uses profiled calender rolls or a roller die system. The profiling allows added rubber to be placed in high lift areas of the tire, equaling out the gauge around the profile of the cured product.

Fabric and steel calendering continue much as they have over the past 30 years, with improvements coming mostly from control schemes. Automatic feedback loops control roll positioning to get a consistent gauge across the sheet. Wire spacing consistency can also be monitored and alarmed. Methods of spreading polyester fabric have improved so that now precise end-count control can be maintained all the way to the edge of the calendered sheet.

In preparing the calendered sheet for use in tire building, the levels of automation increase. Body ply cutting has moved from a manual operation of a saw on a track culling fabric to width, then falling down to a man manually overlapping one piece to the next, to an operation of loading calender rolls on one end and taking cut rolls off the other. Material is spliced automatically, often pre-assembled with other tire components in preparation for the building machine. The newest ply cutters incorporate butt splicing rather than overlapping. Overlapped splices produce a discontinuity in the tire, which negatively influences uniformity and sidewall appearance.

Beads

Tire bead making has taken a large step from the industry standards of a few years ago. Many tire manufacturers have long used a ribbon, or tape bead. A ribbon bead is characterized by a number of parallel steel wires being passed through a die and baffle arrangement that would encapsulate the wires in a rubber matrix. These ribbons are then wrapped around a wheel of a specified diameter until the proper number of wraps are achieved.

The latest bead winding machines use a single coated strand of wire that is stepped over to lay side-by-side, then moved up and reversed, to form the second and subsequent layers. The single wound bead does not have the discontinuity of the splice. This is a more uniform bead, which in turn can produce a more uniform tire.

Tire building

In the area of tire building, consolidation and automation have been a couple of the key changes. Going through a tire assembly area in the late 1970s, one would have seen many bias tire building machines converted over to build radial tires. Material servicers traversed behind the machines to allow for all the components to be fed to the builder. Early radial fires often had upwards of ten components to build the tire carcass alone. The quality of the carcass was directly a function of the person building it.

As we enter the twenty first century, automation has taken much of the personal craftsmanship out of the equation. In many building systems today, the only builder intervention is in making a sidewall or tread splice, if he is needed to do these. The number of components assembled at the machine are less than half of what there were not too many years ago.

Building technology has moved many manufacturers from building on solid deck shoulder set building machines, to bead lock building systems. On a shoulder set machine, the builder builds up innerliner and body ply on a collapsible solid deck building drum. Spring fingers or paddles then wipe down the ply along the side of the drum, providing a vertical surface to set a bead against. In the earliest days, the builder would start the drum rotating, then use metal paddles to turn the ply up. Later advances had mechanical turn up tools that completed this process. On the most recent machines, bladders inflate to turn the ply up on itself.

With a bead lock building machine, the liner and ply are placed on an expanding drum smaller than the inside diameter of the bead. The beads then move across the drum to a specified bead spacing distance. The drum then expands into the beads. Bladders inflate or mechanical stitchers then complete the turn up. The bead lock system can generally build a more consistent, uniform tire than the shoulder set method.

Curing

Basics of tire curing presses have not changed much over the years. Many of the presses from older plants have been rebuilt and given a new life in other manufacturing plants. Autoform and Bag-o-Matic presses, figure 5, are still the standard press curing tires in many plants around the world. These are both mechanical presses that produce the squeeze force by side links and gear reduction. Both presses have large masses that move in multiple planes, which is a source for wear and inconsistencies in the green tire positioning in the mold.

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The current technology in curing presses uses hydraulic pressure to create mold squeeze. Figure 6 shows an example of a hydraulic press. Hydraulic presses have overcome the stigma of being leaky, high maintenance items, to gain a reputation as a high quality curing press. The motion on the top beam of a hydraulic presses is only vertical. This results in better alignment, less wear, and improved tire uniformity.

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With bias tires, two piece molds were the norm. Radial tires followed in similar molds for a number of years. More recently, aspect ratios have decreased. Tread designs have become more complex. The ability to get these tires out of a two piece mold without tearing elements or degrading the uniformity, has diminished. This has necessitated the move to segmented tire molds. The tread segments move in and out radially to allow the curing of the lower aspect ratio and deeper tread tires.

Future manufacturing technology

While the tire manufacturing process has evolved over he past 30 to 50 years, will the future provide similar changes? Count on it, only faster.

Holroyd Associate Limited has taken patents out on equipment that will allow for continuous mixing rather than by batch. This could increase mixing efficiency and could be a quality improvement also (ref. 4).

A new VMI tire building machine can produce a tire every thirty-five seconds. Multiple computer controlled building drums allow for such productivity. A machine like this will require as much manpower behind the machine servicing components, as it does out front building tires (ref. 5). The success of this type of system relies on automation and feedback control.

Some of the tire manufacturers are now working to redefine the way fires are built. Michelin's C3M process throws away many of the paradigms that we use in the manufacture of tires today (ref. 6). Pirelli's MIRS is a similar process (ref. 7). Both take inputs of stock and fabrics, and output cured tires, using a very small amount of floor space.

These processes start by building components up on a drum that stays with the tire through the curing process. Rather than sheets of rubber and extruded profiles, rubber components are produced with a small profiled extrusion that partially overlaps successive strips to produce the desired profile. Rather than calendering and cutting body ply, these methods use a form of weaving the ply to create parallel reinforcement cords (ref. 8).

In conventional tire production, materials are worked, heat is built up and material is cooled a number of times prior to the final curing process. During the production phase of a C3M green tire, no cooling is done. This allows the tire to cure faster as it is already warm prior to entering the curing cycle.

Unlike conventional tire production methods that use a bladder to push the tire out into the mold, the C3M tire closes the mold on the tire. Rather than high pressure steam, hot water or nitrogen, these processes can use electric heat which minimizes overhead to start up this operation.

This flexible set up offers a variety of unique opportunities. Colored tread ribs, as in the BFGoodrich Scorcher T/A line, are now relatively simple (ref. 9).

While the systems like this are flexible, they offer new challenges in both tire and equipment technology.

Summary

As you can see, there remain numerous opportunities to advance the manufacturing and performance aspects of the pneumatic tire through advances in technology. As we look ahead at our economy, several key factors may guide our advancements - conservation of natural resources, the design of active, smart suspension systems and the desire to continue to add convenience and style to the tire (ref. 10).

The automotive industry will likely continue to press the tire manufacturers to design and produce lighter weight, more fuel-efficient tires to help conserve our petroleum resources. A tire produced today can require three to four gallons of oil during the manufacture of the various polymers and tire components - as oil prices rise, both raw material cost and the cost to operate vehicles will rise. This will likely spur the development of new, less oil dependent raw materials that will also provide for lower rolling resistance tires.

With advances in electronic vehicle system components, it will be likely that the tire/wheel system will become an active provider of information to aid in keeping the vehicle under improved directional control and able to stop in shorter distances. The suspension assembly will monitor tire slip rate, deflection, load transfer and air pressure to make real time adjustments to keep all four of the "footprints" optimized on the roadway. Advances in tire design and compounding will help maximize total vehicle performance.

With respect to convenience, the use of more efficient sealant and/or run flat fires will likely increase. As technology improves the run flat tire value, the additional benefit of security that these tires offer will likely be in more demand.

Style-wise, we are already seeing tires with colored tread and sidewall areas to allow a person to customize their individual vehicles. This trend for style niches will likely continue as people use their vehicles to further express their individuality.

While these represent continued technological innovation, the good news remains, that to date, there is no good substitute for the pneumatic tire.

References

(1.) Rubber & Plastics News - "How the modern tire came to be," September 27, 1999, page T-16.

(2.) Cooper Intranet, Passenger and SUV Web Page.

(3.) Stephens, et al. Tire Technology International - "Virtual future at Cooper," December 1999, pp 33-39.

(4.) E. Holroyd and C. Holroyd, inventors, Holroyd and Associates Ltd., assignee; U.S. 5,626,806.

(5.) Alan Baker, Tire Technology International, September 1998.

(6.) Le Pnuematique, "Michelin C3M - The Revolution is on the March!" No. 34, Nov/Dec 1995.

(7.) Rubber & Plastics News, "Pirelli unveils new system," December 6, 1999, p. 2.

(8.) Le Pnuematique, "Michelin MXT/C3M - the 7 Innovations of an Unordinary Tyre," No. 35, Jan/Feb 1996.

(9.) Rubber and Plastics News, "BFG treads roll out in blaze of color," August 23, 1999, p. 6.

(10.) Jeff Yip, Rubber & Plastics News- "Better, smarter, more colorful," September 27, 1999, pp T23-T24.