Minimising rolling resistance has become one of the most important goals in the field of tyre development, and is a key driver for better efficiency and longevity
A primary goal for tyre and vehicle manufacturers is to reduce fuel consumption and carbon emissions in vehicles equipped with internal combustion engines, and to extend the driving range in hybrid and electric vehicles by reducing energy consumption.
One of the biggest contributors to rolling resistance is the energy loss generated in the form of heat, which is called hysteresis. This is the result of the tread and sidewall of the tyre flexing and bending under the vehicle’s weight. The degree of deformation is influenced by the tyre pressure, wheel load, vehicle speed and road surface characteristics. This deformation causes energy to be lost – energy that the engine or electric motor has to make up for. Thus, it is the goal of developers to keep this energy loss to a minimum in order to save fuel or electric energy in the case of EVs.
Tyre manufacturers use specific rubber compounds and tread designs to control hysteresis, with low-hysteresis tyres being designed to minimise deflection, which improves fuel efficiency. This means that reducing rolling resistance is primarily the job of material researchers and tyre designers.
Conflicting goals in tyre development
While reducing rolling resistance involves minimising energy losses, it is the complete opposite when it comes to braking, as the tyre has to dissipate as much energy as possible – which is much more difficult in wet conditions compared to dry roads.
In wet weather, the process of energy dissipation works only if the rubber compound absorbs as much energy as possible during braking. These opposite scenarios – energy dissipated has to be minimised during normal driving and maximised during braking – results in conflicting goals. Accordingly, when developing new components, tyre manufacturers have to always take into account both aspects to ensure that they both remain at a high level.
Developing energy-saving tyres
The development of concepts for “energy-saving tyres” goes back to the energy crises of the mid to late 1970s. In 1980, working in collaboration with and with funding from the German Federal Ministry for Research and Technology, Continental started work on a fundamental study into the design and material-related variables impacting the rolling resistance of commercial vehicles.
This study yielded a whole series of possible solutions. Silica had for the first time largely replaced carbon black, which required fossil fuels in its production. The new filler stabilised the network of bonds among the individual materials used to create the rubber compound. Tyres constructed in this way adhered to the road surface more effectively despite having lower rolling resistance.
Over the same period, Continental’s car tyre research team developed the “cap-and-base” principle, which combines abrasion-resistant tread compounds with shock-resistant tread compounds and thus helps to reduce rolling resistance by up to 15 percent. As soon as the fundamental study was complete, Continental launched a large-scale R&D project codenamed EOT (Energy Optimized Tire) in 1982 with the ultimate aim of developing a tyre with 25 percent less rolling resistance and a 30 percent longer service life.
This project was the starting point for the development of modern fuel-saving tyres and, in 1992, led to the unveiling of the ContiEcoContact for cars and, in 2012, the Conti EcoPlus tyre line for commercial vehicles.
Other technical milestones on the road to the efficiency-optimised tyre included the flat belt concept and finite element method. In 2011, and aimed specifically at the growing market for electric and hybrid vehicles, Continental unveiled the Conti.eContact, the first tyre of its kind to be designed according to the “tall and narrow” principle. It was slimmer than conventional tyres, but had a relatively large diameter.
Since 2020, Continental has been shipping original equipment tyres that are another 20 percent more efficient than the standard class of European tyre label “A”. This innovation was supported by, among other things, the “Green Chili 2.0” rubber compound, which ensures lower energy absorption through the tyre on contact with the road – without any compromises on any of the relevant conflicting goals.
Lower rolling resistance means reduced energy consumption
From a sustainability perspective, it does not make any difference whether tyres are fitted to combustion engine or electric vehicles. Reducing energy consumption is key.
This results in lower fuel consumption for combustion engine vehicles and longer range for electric vehicles and, as long as the electricity used for charging does not originate solely from renewables, lower overall emissions for both drive types.
Jiminy-Ann Bosman
Did you know?
- Minimising rolling resistance is one of the most important goals in the field of tyre development.
- Lowering the rolling resistance of a tyre reduces energy consumption which, in turn, cuts carbon emissions.
- Tyre developers have to meet conflicting goals – energy dissipated has to be minimised during normal driving and maximised during braking.
How-To-Change-A-Commercial-Truck-or-Semi-Truck-Tire
Rolling resistance
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Did you know?
- Minimising rolling resistance is one of the most important goals in the field of tyre development.
- Lowering the rolling resistance of a tyre reduces energy consumption which, in turn, cuts carbon emissions.
- Tyre developers have to meet conflicting goals – energy dissipated has to be minimised during normal driving and maximised during brakin
