Hyundai Motor Group considers each brand’s design philosophy and direction as well as the character of the model when designing vehicles; They incorporate the design language pursued by the brand and its model in every part that makes up the car. The same design language applies to the car’s wheels as well. It has now evolved from just a component that makes a car move, and has become a design element that shows the car’s character. Wheels that differ from the design language pursued by the brand and model may reduce the design uniformity of the car. That’s why automakers make new wheels every time they develop a new model.
The size and width of the wheel is also a design element. It is closely related to the posture of the car. Car designers and enthusiasts often say, “This car has a good stance.” This is an expression of stability or road presence when the vehicle is standing on the ground.
There are many factors that affect the emotional element called ‘stance’ of a car. However, the silhouette of a car that changes depending on the viewing angle has the greatest impact. Factors such as the area occupied by the wheels relative to the size of the car or the size of the tires also affect the aesthetics.
On the other hand, since a car is a running machine, wheels are one of the parts that significantly affect the driving performance of a car. For example, the lighter the parts in the lower body of a car, such as the suspension, wheels, and tires, the more agile the car moves. Lighter wheels help improve handling and ride comfort, and also help reduce the weight of the car.
But light wheels aren’t everything; Recently, the design of automobile wheels has undergone a new change - the beginning of the EV era. In order to make an electric vehicle that can run as far as possible with the same amount of energy, efficiency must be maximized. Every possible detail needs to be meticulously refined to improve fuel economy. Therefore, the wheel design also focuses on improving efficiency.
Improving the aerodynamics of the wheels can reduce the resistance caused by headwinds while driving, which in turn reduces energy consumption. For example, even if there is a difference of only 5% in the void ratio of the wheel, which is, and the ratio of the hole to the area of the wheel, the air resistance coefficient (CD) widens by more than 0.003. For researchers and designers who strive to improve efficiency by reducing air resistance even by 0.001, 0.003 is never small.
Therefore, recent wheels have been improved in favor of aerodynamics. The outer part, such as the rim of the wheel, was flattened or inflated to make it look like a donut. Or, by using plastic and new materials, the void ratio up to 10mm depth of the wheel is minimized. This reduces air resistance by reducing the vortex that surrounds the wheel.
However, the void ratio of the wheel affects the brake cooling performance. Therefore, the design of the wheel must be fine-tuned according to the character of the model; For models that prioritize efficiency, the void ratio is lowered, and for high-performance models that prioritize performance, the void ratio is increased to benefit brake cooling.
In addition, attempts to use geometric and atypical designs that have not been easily used for wheels in the past are also diversifying. In the increasingly fierce electric vehicle market, wheel design is becoming one of the factors influencing design competitiveness. However, this is not all of the obstacles of the electric wheel. For example, an electric vehicle has a larger wheel offset* than that of an internal combustion engine vehicle. As the depth of the wheel decreased, it became difficult to implement a three-dimensional design.
*Offset: the distance from its hub mounting surface to the centerline of the wheel. The larger the offset value, the more the tire goes inside the car body, and the smaller the offset value, the more the tire comes out, making the center of the wheel look three-dimensional.
The wheel of the Kia EV9 is a representative example of wheel design evolving in line with the electric vehicle era. The biggest feature of this is the geometric shapes such as triangles, pinwheels, and squares. This follows Kia’s design philosophy of ‘Opposites United’ (creative fusion of opposite concepts). By using such shapes, it captures simple yet geometric beauty. It is also very impressive that the wheel is seen as an independent work while emphasizing harmony and unity with the overall design, which is the most important factor in wheel design. This is the complete incorporation of the automaker’s design philosophy into the design.
The wheels of the Kia EV9 are also great in terms of performance. In cooperation with the air curtain, it reduces air resistance and energy loss by directing the air flow to the side of the vehicle as much as possible while driving. Plus, it’s lightweight. If the void ratio of a wheel is reduced to less than 8% only with alloy materials, it becomes considerably heavier. Therefore, alloy is used for the body that needs to ensure rigidity and durability, and plastic is used for the cover that affects aerodynamics to complete a wheel with excellent efficiency while being lightweight.
As shown above, automobile wheels are taking on new challenges in the era of electric vehicles. Automakers are overcoming numerous limits with their designs and technologies. In the future, car wheel design will undergo even more dramatic changes; The introduction of more new materials, such as plastic, is giving us more freedom in design. People are also interested in the combination with lighting technology. It is difficult to introduce such technology quickly because of each country’s regulations, but the lights will definitely interact well with the wheels.
Various departments of the Hyundai Motor Group - Exterior Design Team, Tire Design Team, Parts Development Team, and Material Development Team - maare still making efforts to develop new materials and new methods for future wheels equipped with aesthetic design, efficiency, and performance. Hence, the roads of the future will be more colorful, and many are looking forward to more efficient and beautiful cars than they are now.
Thanks to senior researcher Seung-tae Kim and Hyun-soo Kim, from Kia Exterior Design department
HMG Journal Operation Team
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