Tech Focus: Bugatti T35 Alloy Wheels

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When looking at pictures of 1920s grand prix races, the Bugattis always stand out for some reason. It can be hard to put your finger on exactly why that is: they all have a similar cigar-racer shape with a pointy rear end, a tall radiator at the front and bicycle-tyre-narrow, free standing wheels. But look closer and it is the latter that sets the Bugattis apart from all their contemporaries. When all other cars were running on wire wheels, or even wooden items for the more pedestrian models, the Bugatti Type 35 was the first car to feature aluminium alloy wheels.

Bugatti was an immense innovator, with the result that his racing cars were hugely successful. Two problems racing cars had in those days were unsprung weight and brake cooling. The then‑common wire wheels may look delicate and pretty, but were never very light, while pressed steel wheels were still some way off. Bugatti, meanwhile, figured out how to cast a molten aluminium alloy into a wheel shape that was both much lighter than wire wheels, but still strong enough for racing. Today, this type of wheel may be ubiquitous on anything from a small hatchback to a supercar, but it took a long time for alloy wheels to be democratized

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The second thing that Bugatti’s alloy wheels had over wires was heat dissipation. Keeping the massive drum brakes cool was one of the biggest challenges of racing. What Bugatti did was integrate the drums into the cast wheels, so that the conductivity of the metal would make the large spokes act as a heat sink, ferrying the heat away. This gave them a great advantage over the conventional setup, which relied only on the air rushing by for cooling the brakes.

As with all new technologies, there were some teething problems. Back then, there were no standards for rim and tyre design like there are now. Manufacturers of cars and tyres were still figuring out what the best way was to make a tyre stay on a rim. Bugatti figured that bolting a cover onto the wheel to hold in the tyre would be the optimal solution. Not being able to find exactly the right size tyre, this resulted in the tyres being ripped off the wheel.

Compared to some of today’s LSD-trip designs (and we’re not talking about differentials here), the Type 35’s 19” wheels may look quite crude, but they were an innovation that has defined the look of today’s cars.

Automobilrennen auf der Avus 1932 – Bundesarchiv (bundesarchiv.de)