Since 2004, a rim has been defined as “the support for a tire and tube assembly or tubeless tyre, on which the tire beads rest”.
In the early years of the automobile, the tire was glued to the wheel, which was made of wood, and repairs were long and tedious. We had to wait for the invention of the removable tire by the Michelin brothers to discover the benefits of a steel rim; steel sheet, which became widespread in the 1920s.
Heat is a problem
When manufacturers switched to sheet steel rims, the primary concern was heat dissipation from the brakes, hidden behind a curtain of metal.
These drum brakes, when they got hot, lost their effectiveness when braking the car. We then started drilling holes in the rims to improve cooling.
But the weight was still significant, which adversely affected the smoothness of the ride due to their inertia. For competition, we found spoked discs that made cooling easier.
Aluminum alloy response
It took the genius of Ettore Bugatti to overcome these problems. You need to go back a little. In 1886, inventor Charles Martin Hall and chemist Paul Héroux independently developed an electrolytic process to extract aluminum.
In 1920, racing car designer Harry A. Miller came up with the idea of making aluminum wheels. He applied for a patent but ultimately did not produce the wheel.
Alloy wheels for Bugatti 35
Only a little later, Ettore Bugatti, the founder of the famous brand, managed to cast aluminum wheels and brake drums in one of his foundries, using molds he even made.
Always a perfectionist, Bugatti files over 500 patents with new ideas for its wheels.
In 1924, the Bugatti 35 replaced the spoked wheels with eight-spoke aluminum alloy wheels.
For the first race in September 1924, it was a disaster; all the cars gave up. Due to poor quality tyres. Cast aluminum will continue on its way.
At the time, the wheels accounted for about a quarter of a car’s aerodynamic drag. Ettore Bugatti believes that with well-designed rims, better distributed airflow will result in better heat dissipation.
In competition, it is very important to be able to quickly remove the heat generated during braking. Good cooling is the key to more efficient braking. The interest of Bugatti’s flat spokes was to dissipate hot air without building up heat.
Forged or cast rim
There are two types of alloy wheels today: cast (for standard or economy production) or forged and then machined for top models. A technique that allows you to create a wide variety of drawings.
Among the advantages is that they are lighter than sheet steel wheels, which gives the car more liveliness.
On the other hand, they can easily get scratched and lose their shiny look. Finally, it is not recommended to install winter tires on alloy wheels; their reduced weight does not allow a winter tire to grip as well on slippery surfaces as if it were mounted on a steel rim.