An industry initiated by rim size and ending with rubber composition

An industry initiated by rim size and ending with rubber composition

 By Ertugrul Bahan*

Until 1990, the main performance criteria of a tyre were traction, wear and temperature, mainly durability. Later, the speed of passenger cars almost doubled with the radialisation of tyres. Greater stability is needed with increasing speeds and a larger interior space of the vehicle is provided for comfort reasons. As a result, body and chassis weights are significantly increased with these new trends for the same vehicle category. New engine technologies provided moderate fuel consumption and optimized engine performance and efficiency supporting these trends. Increasing overall weights and higher speeds naturally required more powerful braking systems. This has resulted in heavy and secure wheel systems.

Large brake pads and rotor surfaces required rims of large diameter. Anti-block systems and more robust braking equipment are applied by all vehicle manufacturers. These development steps shortened the stopping distances of the vehicle. The new generation rims, larger and wider, had a significant weight advantage with composite materials and alloys. Today, the rims are not heavier than the previous generation although the mass volumes are doubled.

In general, tyres are not very lucky, unlike rims, because of the dynamic performance requirements. New generation tyres are wider for safety reasons. Their size and weight have therefore been increased while each of their revolution consumes more energy. Internal frictions at each turn create a loss of heat and energy, usually called rolling resistance. The lightweight vehicle equipment and tyres with low rolling resistance are demanded by the automotive industry and rolling resistance and improved wet traction remain key and competitive issues in tyre industry. As a result, fuel-efficient green tyres in future, designed to minimize rolling resistance, represent the fastest-growing segment of the tyre industry.

Roles of tyres, rims as design parameters

Tyres and rims, which are the most important part of vehicles because of their rolling action, have always been at the heart of safer and more economical vehicles. The size of the tyres depends on the weight of the vehicle, the weight distribution and the engine torque. “The automotive engineer sets clear goals for tyre manufacturers”. This includes specified wheel loads, braking distances, revolutions and rolling resistance as measurable parameters. The requirements of tyres are much more precise for UHP and upper segments. Once the prototype tyre is ready, the test pilots begin to subjectively evaluate the characteristics behavior on dry, wet, snowy or icy surfaces.

Monoply is a big step changing design philosophies

The strength of tyre carcass cords has doubled over the past 50 years with the same weight in grams of new materials. This has helped tyre engineers extending monoply designs into larger tyre sizes, opening horizons for optimal comfort and rolling-resistant designs. After lightweight body ply, today passenger car tyres’ 85% of the weight comes from rubber of all components. Tyre rubber composition, therefore is main contributor of rolling resistance effect due to the rolling hysteresis.  The main hysteresis took part on the tread which consists of the main part of the rubber volume. On the basis of this, narrower temperature window is key parameter by automotive industry.

Automakers are advocating tighter tyre temperatures to reduce vehicle emissions and achieve fuel economy goals. This requires low-rolling resistance tyres and accelerates their entry into the original equipment market. The growth of alternative propulsion systems (hybrid and electric) and the use of autonomous vehicles, which continue to favor the introduction of green tyres, required a further reduction in rolling resistance.

Art of design provided by rubbers and fillers

Tyre design is the art of optimising many parameters to achieve their goals. For example, wet grip and rolling resistance have the opposite effect if we want to improve them with standard materials. Silica / silane technology solved this problem and some rubber structures replaced 95% of the carbon black. Silica / silane technology has become the standard for car tyres in Europe.

As a result, tyre manufacturers offer sustainable tyre technologies, including renewable rubbers in their products and offer performance comparable to or better than conventional rubbers. Many tyre manufacturers have entered into strategic partnerships with governments, researchers and biotechnology companies to support their efforts to develop rubber from renewable resources on a commercial scale.

Green materials and future trends

For example, some tyre manufacturers are currently looking to use dandelion flower oil as a future ingredient in their production process. At the same time, some are also trying to include soybean oil in the manufacturing process, as this would reduce the amount of oil obtained.

The research on “greener” tyres seems to be endless in the tyre industry and the rubber composition containing greener ingredients will be very popular in next years. Yes, “Rim Size Starts the tyre design that ends with the decision of rubber composition”. This article draws your attention to the relationship between vehicle and tyre design and why the chosen rubber is essential. Tyre Asia’s Asian Tyre and Rubber Conference (ATRC) which focused on “technological and innovative excellence in green production,” is a pioneer on this path to the future.




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