The Effects of Capmax on Tire Rolling Resistance

Global warming is a tremendous concern in modern times and the transportation sector was responsible for 14 percent of 2010 global greenhouse gas emissions. Fossil fuel use remains the main source of CO2, and therefore reducing fossil fuel consumption will decrease CO2 emissions. In order to minimize greenhouse emissions, stricter emission goals are being set by car manufacturers. By 2020, the EU CO2 automobile emissions target is 95 grams of CO2 per kilometer and the target for 2025 is in the range of 68–78 grams of CO2 per kilometer.

In order to achieve this goal, car manufacturers have strict rules and select Original Equipment tires (OE tires) in order to limit CO2 emissions. So, tire manufacturers are now enthusiastic to reduce tire weight and rolling resistance without losing other tire performance parameters.

While a tire rolls on the road, mechanical energy is transformed into heat due to the phenomenon known as rolling resistance. Hence, rolling resistance dramatically affects the total fuel consumption of any vehicle.

 In The Pneumatic Tire, a book published by the US National Highway Traffic Safety Administration (NHTSA), rolling resistance is defined as follows:

“Rolling resistance includes mechanical energy losses due to aerodynamic drag associated with rolling, friction between the tire and road and between the tire and rim, and energy losses taking place within the structure of the tire.”

Various factors cause increased rolling resistance, including wind drag on the car, friction between the road and tread of tire and tire distortion due to hysteresis of tire materials during deformation. Hysteresis losses are the leading cause, and almost 90 percent of tire distortion can be connected to viscoelastic behavior, which means that tires dissipate additional energy in the form of heat when the cord and rubber components of tire materials are deformed [1]. It is well known that rubber compounds have a bigger effect on tire rolling resistance than tire cords. Adaptation of tire cords to reduce rolling resistance is mainly aimed at lowering tire rolling resistance by reducing the rubber volume in the crown area.

Three main deformation types are dominant on the contact patch of the tire: transversal bending of the crown, sidewalls and bead area, compression of the tread, and shearing of the tread and sidewalls. In generally, while 70 percent of energy dissipation occurs in the crown area, energy dissipation is equally distributed in the sidewalls and bead regions of tire structures. Several external factors affect rolling resistance as well: load, inflation pressure, longitudinal velocity, applied torque, tire radius, width, and tire’s operating temperature. It should be noted that load increase is almost perfectly correlated to increases in tire rolling resistance[2-3]. So, many tire manufacturers intend to use low rolling resistance structures and tread compounds in order to reduce the weight and rolling resistance of their tires.

Looked at this way, Kordsa offers an innovative product for tire manufacturers. Kordsa has developed a ready to use cap ply solution—Capmax®—which is engineered as an eco-friendly replacement for calendered tire cord fabric as a cap-ply material. Capmax® strips can be directly applied to the tire during the manufacturing stage, reducing the use of rubber in cap-ply as well as eliminating many stages in tire production, such as rubber preparation & mixing, calendering and the slitting of rubber coated fabrics. Tires manufactured with Capmax® consume less resources, energy and raw materials and contribute to reducing the carbon footprint and rolling resistance of the tire.

For instance, when a 205/55 R16 91H tire is replaced with a Capmax® NY 940x2 construction, almost 280g of rubber compound is saved and rolling resistance of the tire is reduced by 3.5 percent when compared to calendered rubberized cap ply. The effects of Capmax® NY 1400x2 on rolling resistance can be given as another example: the amount of rubber compound is reduced by between 100–200 g when Capmax® is applied to one layer as a cap-ply. Also, the rolling resistance of the tire can be reduced by 2 percent when compared to calendered rubberized cap ply.

Discover the Capmax: www.kordsa.com/capmax

References:

[1]- Akutagawa, K. Koide, M and Heguri, H. (2003). Application of non-linear FEA to tyre rolling resistance simulation. Constitutive Models for Rubber III: Proceedings of the Third European, p.175.
[2]- The Tyre - Rolling Resistance and Fuel Savings. (2015). 1st ed. [ebook] Michelin. Available at: https://community.michelinchallengebibendum.com/docs/DOC-3212 [Accessed 8 Jun. 2017].
[3]- LaClair, T.J. (2006). Chapter 12: Rolling Resistance. In: 1st ed. National Highway Traffic Safety Administration, U.S. Department of Transportation, pp.476-500.

BAHADIR KAYA

Project Leader, Global Technology Center

 

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