When we discuss about a motorcycle's performance, we generally speak about its engine power, torque, top speed, how fast it can accelerate, vehicle sound etc. Nevertheless, all these are meaningless if a driver cannot control the machine and/or is not comfortable while riding. There comes the importance of tyres. Tyres are the most crucial parts of a vehicle suspension system.  Tyres are the only component in a motorcycle that constantly stays in contact with the road. The part of tread which is in contact with road surface is called ‘contact patch’ & Is about half the size of a post card.  The overall suspension system (including tyres) ensures the right contact between the tires and the road surface at every stage of driving, thereby ensuring stability and good handling of the vehicle.

As tyres are the only contact with the road, they are responsible for multiple functions, such as –

Transfer the engine power to the road- meeting the demands of acceleration and braking

  Provides right hold (grip) on different surfaces like dry, wet, snow, loose soils etc.

  Helps the rider to steer the vehicle by responding to the handle movements

  Carry the weight of the vehicle & rider

 Ensuring the comfort of the rider by absorbing and dampening shock

Apart from the above aspects, tyres play a vital role in vehicle aesthetics, safety, fuel efficiency etc. These and several other challenges make Motorcycle tyre design a very interesting and responsible subject.

Apart from being a crucial part of a vehicle suspension system, tyres are the only contact between vehicle & road. Motorcycle vehicle dynamics and control characteristics are highly influenced by the tyre design. It is therefore highly imperative for a vehicle chase/suspension designer & tyre designer to work together in tandem. This will ensure that the part designs will complement each other and deliver the characteristic target performance of a motorcycle. A robust interaction mechanism between the R&Ds of OEM [Original Equipment Manufactures] and tyre manufactures is a growing necessity to cater to the ever‐increasing demands of performance entrusted upon the tyre of today. In case of tyres getting designed exclusively for aftermarket, a tyre designer work closely with the vehicle dynamics team to ensure that the retrofit design delivers desired target performance of the vehicle

Some of the major steps involved in motorcycle tyre design are

 Product planning & Tyre “Size” finalization: During this stage a vehicle designer & tyre designer jointly review the vehicle performance requirements and decides the parameters specific to tyre performance. This includes:

Defying the application /terrine: Depending on application, 2 wheelers maybe broadly classified as Sport, Cruiser, Choppers, Touring, scooter, Step through, Sport touring, Enduro etc. Different OEM’s follow different terminologies, but a for a tyre designer to understand the final use by the user is of utmost importance. Demands from a tyre varies with each vehicle category, for example, for a cruiser the tyre is designed to be robust so as to hold up the weight of such heavy bikes and deliver long tyre life, whereas for a Sport touring /super sport bike, tyres are  designed to deliver quick and precise handling with superior grip. These tires are lighter and made by using softer compounds for Superior grip.

Selection of Bias /Bias belted / Radial:   At this juncture, I am not going to delve deeper into a detailed comparison of these constructions – however, it is important to acknowledge that both these construction types have their respective advantages and disadvantages. Each of these constructions has few specific applications where one performs better than the other. The selection of construction type mainly depends on vehicle category (application), vehicle Speed, load on the tyre, stability requirements, handling requirements, etc. for example Bias tyres are used in medium speed but heavy weight vehicles owing to their sturdy sidewalls, whereas Radial tyres are the ideal choice for high speed , vehicles because of their superior dimensional stability.

Selection of Tube type Vs Tubeless:  Functionally both types of tyres have a proven track record for almost all applications. Hence this choice mainly depends on vehicle Rim design, which is decided by the overall aesthetic demand & application of the motorcycle.For high speed application, tubeless is always preferred

Finalizing the Tyre size / Tyre Geometry:  In general, we may call it as tyre “size” – which includes tyre width, tyre diameter, rim diameter etc. Tyre geometry affects the vehicle dynamics like caster, trail, vehicle Center of gravity [CoG], etc. It also influences the area of contact between vehicle and road surface under different riding conditions & load-carrying capacity of the tyres. Furthermore, tyre size significantly influences vehicle aesthetic as well.  Tyre “size” and vehicle rim size are always interconnected. Decision on one influence the decision on the other.  Usually motorcycles have different front and rear tyre sizes depending on vehicle geometry & load distribution. Tyre “sizes” are decided considering all these parameters & the designers ensures that it follows the standards’ guidelines applicable in target countries.

Tyre tread profile design:

Contrary to the passenger car tyre designs which have almost flat tread surface, motorcycle tires have a U-shaped profile and a contact patch that changes size and shape during cornering. There is a major difference in the way lateral force is built up in passenger car and two wheelers.  In case of passenger car, mechanism of lateral force builds up is due to slip angle whereas in two-wheeler it is mainly because of the camber or the leaning of the vehicle.  Hence you see a flat tread area for passenger car tyre and U-shaped profile for Motorcycle tyre

This U-shaped profile is an important design factor having a direct influence on vehicle performances such as drivability (handling) durability, ride comfort, noise and wear resistance etc.

These tread contours are designed as the arc of one radius, or a combination of arcs with two or more radii. These profiles ensure the required contact patch availability at different lean angles & are controlled by the lean characteristic of the vehicles. It is very critical to balance the performance of front tyre & rear tyre of s motorcycle for precise handling of the vehicle. The contour designs play an important role in front /Rear tyre balance.

Tyre tread pattern design:

Patterns are molded in the tread area of tyre by repeated arrangement of ‘Groves’ or ‘Blocks’ & are generally referred to as “tread pattern”.

Significance of tread pattern: 

Tread pattern plays a vital role in tyre performance such as:

Optimizing the traction on the riding surface

Eliminating aquaplaning

Optimizing the” Wear” of tread area·  

Ensuring the continuity of tyre performance at different wear Stages [ wear %] of tyre.

Rolling resistance of the tyre

Noise generation

roviding a measurable clue to the owner on time for removal /suitability for continuous usage. etc.

Tread patterns not only helps in achieving the target performance, but also impart unique look to tyres and enhance aesthetics

Tyre patterns are broadly classified into 4 Major headings

• Rib patterns
• Directional
• Block [ Knobby]
• Slick tyres [Pattern less]

Selection of which group of patterns is mainly controlled by the terrain of application, e.g. Directional patterns are preferred in paved roads and knobby pattern ae mainly used on off-road applications. Pattern less tyres are normally used in racing track applications to provide maximum traction.  Vehicles are designed to work in a combination of different terrains – similarly, tread patterns also have subgroups– which are optimized to operate in different combination of terrains. E.g. Semi knobby patterns for on – off allocations, High land – minimum grove patterns for Supersport highway applications etc.

Designer alter the direction of the grove, depth of the grove, number of groves, the ratio between Grove area & non grove area [ Land- sea ratio] , shape of the grove, the width of the grove etc. to optimize the performance of tread pattern. These patterns are designed to perform under different dynamic conditions. Nowadays designers seek the help of computer-aided simulations to predict the performance under different loading /riding conditions to optimize the pattern design.

Tyre as an Aesthetic component

The visual appeal of tyre is significant contributor in the overall aesthetics of a motorcycle. Hence in addition to performing all the functional requirements discussed so far, tyres ought to look good too.

The tread pattern should complement the overall styling language of a motorcycle. This attracts the attention of OEM’s vehicle styling studios towards tyre tread designs as well. In fact, most of the new tyre designs are done first at styling studio and then technically optimized by the tyre engineer to guarantee the functionality.

Material design

Tyre is a composite material made of different rubber compounds and reinforcing materials. Right compound and reinforcing material selection are crucial to achieve the target performance of tyre.

• Reinforcing materials:

Reinforcing materials provides the required strength and stiffness for tyre body [carcass]. This includes “tyre cords” used in tyre body ply & “bead wires” used in bead construction of tyres. Most used tyre cord materials are Nylon 6, Nylon 6-6, Polyester, Aramid, Rayon, Steel, etc.

These materials differ in their chemical composition, tensile strength, elongation properties, impact strength, temperature resistance, rubber adhesion, etc. Tyre engineer must choose the right tyre cords depending on the performance demands of the tyre like load carrying capacity, durability, impact resistance, drivability, speed of operations etc. Cost & availability also are few decisive parameters during selection of reinforcing materials.

Tyre Cord denier, cord style, EPI (Ends Per Inch), angle of cords and number of plies affect the strength of a tyre and are chosen based on engineering, and design criteria.

structural durability of a tyre is Primarily determined by the reinforcing material

• Rubber compound design

Each part of the tyre must dispense different functions and are thus designed with different rubber compounds like tread compound, sidewall compound, carcass compound, bead wire coat compound, etc.  Though all these compounds have their own importance, but tread compound selection is the most critical, as it has a direct impact on tyre traction, handling, wear performance, durability, rolling resistance, etc.

• • Trends of tread compound design:    

Even though smaller number of components are used in a motorcycle tyre, than as compared with passenger car tyres, but performance challenges involved in compounding are far more complex considering less area of tyre in contact with road. 3 major performance requirements in motorcycle tread compound are (1) Grip (2) Rolling resistance [fuel efficiency] and (3) Tyre life which is generally referred as the magic triangle in tyre rubber compounding. This is due to the contradictory response of these 3 performance characteristics to rubber compounding approach. For example, improvement in Grip normally comes with an increase in rolling resistance with conventional compounding as both are related to energy loss. It is always a challenge for tyre compounder to improve all three performance requirements together and this calls for the incorporation of advanced polymers and fillers.

Performance priorities for tread compound changes based on operating terrain, type of vehicle, etc. e.g. Street two-wheeler tread compound designs primarily focus on high grip and high-speed capabilities, whereas an on-off application tyre require higher cut and chunk resistance tread compound.

Demand for lower rolling resistance tyre is showing a steady increase Year-on-Year. Major divers for this growing demand are Electric vehicle introduction & increased focus on vehicle fuel efficiency, in few segments. Tread compounds are expected to deliver lower rolling resistance, without compromising the Grip – typical “magic triangle” puzzle for any tyre compounding engineer. Tyre industry can address this challenge by usage of new generation materials like SSBR, functionalized SSBR, high molecular

Design for manufacturing

For success of any product – Design & manufacturing sync is a must. While designing, to accommodate all functional requirements, a designer cannot ignore the significance of manufacturing process. Hence every tyre design is optimized to satisfy both functional & manufacturability needs. This if not done properly may result in suboptimal performance of the product,

Product Performance Testing

It’s important to review and verify the product performance before releasing it into the market. There are a set of Indoor & Outdoor tests for performance review. A few of them are listed below,

Indoor tests: High-speed drum test, Endurance test, Rolling resistance test, Force and moment testing, Stiffness test, Footprint etc.

Outdoor tests: Ride and Handling testing (track, off-road, public road etc.], Braking test [wet, dry], tyre wear test etc.

Blend of Engineering & Art

Being an integral part of vehicle suspension system & only contact point with road, a tyre plays significant role in motorcycle performance [safety, drivability etc.]. In addition to these performance parameters, tyres have significant influence on the overall styling of the vehicle. It complements the primary theme of the vehicle. A right blend of engineering and art is essential for a successful tyre design. One cannot substitute the other. Amongst different steps of tyre design like, dimension finalization, tread design & martial design etc. the most critical step is tread design (profile, pattern & compound)

Few areas designers are focusing today to  meet the near/middle future demands are

• Lowering the rolling resistance – without compromising grip
• Shortening the time to market.
• virtual simulation of tyre performance

 

References

1.  ‘’The pneumonic tyre’’, National Highway Traffic Safety Administration, Feb 2006
2. T. French, Tyre Technology, Hilger, New York, 1989.
3. Mechanics of Pneumatic Tires, S. K Clark, ed., University of Michigan, US Department of Transportation, National Highway Traffic Safety Administration, Washington, DC, 20590, 1891.

     4.  Handbook of vehicle-road interaction: vehicle dynamics, suspension design, and road damage / edited by David Cebon. p. cm. - (Advances in engineering), ISBN 9026515545

    5. “Tyre and Vehicle Dynamics” , Hans B. Pacejka,  Professor Emeritus Delft University of Technology, Consultant TNO Automotive Helmond

     The author is General Manager - Product Development,2&3-Wheeler tyres, CEAT Tyres

Hankook Tire revealed the Design Innovation 2020 project, which defines a vision for the future driving and innovation in mobility.

Launched in 2012, the Design Innovation is Hankook’s R&D project held every two years, in collaboration with one of the world’s leading design universities.

Under the theme ‘Urban Reshaping’, professors and students from the Department of Industrial Design at the University of Cincinnati in the U.S. focused on the transformation of cities geared by reconfiguring mobility as part of living spaces rather than stand-alone purpose in the future with augmented automation infrastructure and cutting-edge technologies such as eco-friendly technology, autonomous driving and Artificial Intelligence (AI).

Throughout the project, modular platform of mobility concept named ‘Hankook Platform System (HPS)-Cell’ was proposed with tyre representing the root of mobility. It is applied with ‘Hankook Electric Mobility Technology (H.E.M.)’ which represents Hankook’s passion for future technological breakthroughs. Then a scenario was created which distinguishes mobility as a moving platform and its function as a pod (space), clearly elaborating that tire indeed sits at the center of the mobility.

The tyre of HPS-Cell embodied an airless tyres’ double-layered unit-cell structure to acquire complex rigidity. It is a concept tyre that uses sensor technology to not only identify tire treads and road conditions in real time, but also to respond to wear-out risks and change tread patterns according to the road condition utilizing variable wheels and optimized infrastructure.

The scenario was brought into reality in a concept film and a mock-up. The productions suggest that in 2040 urban population will be able to use this mobility platform combined with pods of various forms to each meet a specific purpose. The modular platform can also be combined with commercial pods such as urban farming to maximize the scalability and efficiency of movement within smart cities of future generation.

The unveiled productions will be exhibited at various global channels and will represent Hankook’s capabilities in design innovation globally.

Jimmy Kwon, Vice President of Hankook Tire Brand Lab said, “Hankook Tire is incorporating new ideas with our cutting-edge technology to explore design concepts for the next generation, as Hankook believes creativity is the first step towards bringing the imagination into the reality. We are more than excited to present this year’s works as they speak for the essence of the future mobility that Hankook envisions.”

TATNEFT has announced the development of a new line of ATV tyres called the KAMA Quadro ATM. The first model has been made in 25x8-12 standard size at its Nizhnekamskshina factory in Russia.

The ATV tyre, which is developed by Kama Scientific and Technical Center, has been specially designed for off-road driving, providing excellent cross-country ability in mud and snow. The tyre’s special rubber composition ensures high reliability and traction performance.

The first batch of tyres will go for pilot testing to TATNEFT subdivisions that operate off-road special vehicles.

The KAMA Quadro ATM range is currently being developed in nine tyre sizes covering 12 to 14 inches diameter, with nine more sizes coming up over the next year. The factory will begin production of 25x10 tyres for the rear axle in addition to the already manufactured  25x8 tyres intended for the front axle.

The KAMA Quadro ATM will meet the needs of the TATNEFT Group’s all-terrain vehicles used in oil fields and will also be used to equip Russian ATV manufacturers and the secondary market. (TT)

Kumho tyres have outperformed 52 rival manufacturers to ace the Auto Bild magazine’s summer tyre test with its ECSTA HS51 high-performance pattern tyre.

The annual test is among the most comprehensive of its type, the results of which are regarded as highly significant by both the European tyre trade and its consumers.

Conducted on both wet and dry surfaces, it left Kumho in a fighting third place overall. However, while the further qualifications caused the two leaders to slide down the order, 33 of the 53 entries were eliminated by the initial braking test. Kumho’s highly competitive and consistent scores in almost every discipline ultimately left it as the sole test winner.

 Awarding the ECSTA HS51 their coveted ‘Exemplary’ badge, the Auto Bild testers commended it for its precise steering response, secure wet grip, well-balanced handling, short braking distance, low wear rate and affordable price.

Unlike some tyre tests, where the products are supplied by the manufacturers, those for the Auto Bild ones are covertly purchased by the magazine from regular retail outlets. The chosen size was 205/55R16, the direct fitment for the bulk of Volkswagen Golfs and Audi A3s etc., and therefore arguably the one most common within the European car market.

UK purchasers currently have the choice of 35 sizes of ECSTA HS51 for wheels of 15 to 18 inches in diameter. The qualification round of the test was carried out at ATP (Automotive Testing Papenburg) in Germany and the other tests were performed at the IDIADA facility in Spain. 

Thus, our newly developed "Tire Leap AI Analysis" utilises advanced AI-based analysis technology to analyse (for example) electron microscope imagery of tyre rubber compounds in order to achieve high-precision analysis that far exceeds human capabilities, thereby making it possible to derive accurate estimates of rubber properties from structural data found in this imagery.

 

Specifically, it is a technology that estimates rubber properties precise from combining data on the individual raw materials contained in a rubber compound with data on its internal structure. In the future, we will continue to develop this technology and develop technology to estimate the future rubber properties from electron microscope imagery of unused rubber.

■ Technology to Precisely Estimate Rubber Properties Based on Structures & Materials

 

Tire Leap AI Analysis utilises an AI-based image analysis system to analyse the internal structures of rubber in images captured by an electron microscope in order to infer information about the properties of the rubber based on its structural data (i.e. the results of image analysis). By combining this structural data with data about the materials that make up rubber compounds, this technology is then able to derive information about the physical properties of rubber with a high degree of precision.

■ Technology to Detect Changes in the Internal Structures of Rubber After Use & Estimate Resulting Changes in Rubber Properties

By comparing images of a tyre that has never been used (i.e. that is brand new) with images of a tyre that has been used (i.e. after wear over time), this AI-based image analysis system can determine where changes have occurred in the internal structures of the tyre’s rubber and then estimate the physical properties of the rubber in the areas that have undergone these changes. The practical application of this technology will facilitate the design of new rubber compounds that are less prone to performance degradation due to wear and tear, thus contributing to the development and advancement of Performance Sustaining Technology.

Dr. Miki Haseyama, Hokkaido University: We have developed a new AI technology that is able to estimate the extent of changes in the structures based on analysis of images of the internal structures of rubber. As compiling data for this kind of machine learning would otherwise be extremely time-consuming, one of the main merits of this new technology is the fact that this AI does not require prior field data from structural changes in rubber for machine learning. Rather, this AI uses deep learning to learn about the properties of new rubber (i.e. prior to undergoing structural changes) and then estimates the extent of changes in the structure by analysing how data from old rubber (i.e. after undergoing structural changes) compares to the data that it has previously learned about new data. This approach to machine learning allows the AI to automatically detect various types of changes in the structures of rubber.

Kiyoshige Muraoka, Senior Executive Officer, Sumitomo Rubber Industries: We have been working jointly with Hokkaido University to further advance the development of AI technology that can understand how the internal structures of tyre rubber change through use. We have already put this new technology to use in the development of our latest “ENASAVE NEXT III” fuel-efficient tyres, which not only achieve the highest possible “AAA-a” rating for fuel efficiency and wet grip performance (under Japan’s tyre labelling system), but also reduce changes in tyre performance that occur over time as a result of use by half. Moving forward, we will continue to advance our Tire Leap AI Analysis technology to find and analyse slight variations in the internal structures of rubber that human senses and knowhow have been unable to detect so that we can then use the resulting knowledge to develop new technologies that further enhance tyre performance and ensure that this high performance lasts longer. In this way, we will accelerate research and development toward producing high-performance tyres that provide greater safety and peace of mind with the aim of contributing to the realisation of a sustainable mobility society for future generations.

 

References:

Ren Togo, Naoki Saito, Takahiro Ogawa, Miki Haseyama, “Estimating regions of deterioration in electron microscope images of rubber materials via a transfer learning-based anomaly detection model,” IEEE Access, vol. 7, pp. 162395-162404, 2019.