Engineering Philosophy
A high quality wheel requires all three elements: light weight, stiffness, and strength.
STIFFNESS: Stiffness is the basis of wheel performance. What is “stiffness”? If a rim is stiff, it will resist deformation when it is subjected to force. Although we consider metal as “hard”, metal does have a tendency to deform when force is applied and return to the original shape when the force is eliminated. Stiffness is often confused with strength, but it is different as strength is a measure of tendency toward breakability. To make the best out of today’s high-performance tire, wheels need to have high stiffness to keep the proper connection between the chassis and tires. On the other hand, wheels with low-stiffness could easily be deformed by the load from the tires. Enkei recognizes stiffness is the most important element for high performance wheels.
ALUMINUM EXPLAINED: PRODUCTION METHODS WILL NOT AFFECT STIFFNESS
How can we increase the stiffness of wheels? As long as wheels are made of aluminum alloy, using a different production method does not affect the stiffness of the wheel. That’s because all aluminum alloys used for forging and casting create same material property with identical stiffness.
Comparison of Wrought aluminum alloy and Cast aluminum alloy
* Young’s moduls is a measure of elasticity, equal to the ratio of the stress acting on a substance to the strain produced.
You may think forging process creates stronger materials. However, when forged and cast aluminum alloys are measured by the Young’s modulus, it shows almost no difference between two methods. Forged and casted aluminum alloys are nearly identical in specific gravity as well. Therefore, if you make an exact same shape of wheels using forging and casting method, the weight of those wheels should be the same. What is the advantage of the forging process, then? It is an ability to produce higher material strength.
Generally speaking, compared with casting, forged material is superior in yield strength and tensile strength. However, no matter how great the material strength, it cannot justify an extreme reduction in weight.
Even with adequate material strength, if wheels lack stiffness, they cannot perform properly even with high-performance tires.
Durville Die Casting & MAT Process
Enkei has adopted two technologies – the Durville die casting and MAT process that ensure cast aluminum wheels have strength comparable to forged ones. In the Durville process, molten aluminum alloy is poured into the mold from its inner rim side, with the disc side facing downward. The alloy is rapidly quenched and solidifies, starting at the disc side, creating a finer metallic structure, significantly enhancing tensile strength, yield strength and elongation.
In the MAT process, the wheel rim placed on a mandrel is spun and rolled. This spinning process creates “metal flow” in the metal structure of the aluminum alloy, which is similar to the metal property seen in the forging process.
This hybrid process of casting and forging gives wheel high material strength while keep manufacturing cost more affordable than forged wheels. Additionally, it gives greater freedom of design on the wheel face.
Design Capability behind the best wheels
How does Enkei ensure its wheels have high stiffness? The answer is Enkei’s “Design Capability”.
To maintain high stiffness under great force, the wheel’s cross sectional area in the direction against the force applied needs to be enlarged. Unfortunately, the larger this area is, the heavier the wheel will get. However, if the layout, cross sectional shape of the spokes and the rim profile are designed properly, the wheel can maintain high stiffness without
adding weight.
The layout is made possible by Enkei’s vast accumulation of wheel design data and the computer aided engineering 3D simulation. In addition, Enkei strives for the largest possible weight reduction by identifying the wheel portions where stress concentration is least likely to occur and shaving down areas that do not affect stiffness.
Enkei’s processing techniques ensure the “strength” of its wheels, and its excellent design capability ensures “stiffness” and “lightness.” Enkei’s design capability is the most-treasured asset and essential for developing the highest performance wheels.
