Wheel Aerodynamics: Why EVs and Performance Cars are Returning to 'Dish' Designs
In our previous discussion about Wheel Physics, we noted how F1 cars returned to wheel covers to reduce drag. This “Dish-style” design, once a trend in the 80s and 90s, is making a massive comeback driven by the rise of Electric Vehicles (EVs).
When we pursue fuel efficiency and range during high-speed cruising, the wheel is no longer just a structural component—it is a critical aerodynamic tool.
1. The Invisible Wall: Ventilation Drag
When a car moves forward, air doesn’t just hit the front bumper. A significant portion of air is sucked into the wheel wells. As the wheels rotate at high speeds, the spokes act like the blades of a centrifugal fan, violently churning the air.
This phenomenon creates Ventilation Drag. Scientific studies in wind tunnels show that:
- The wheels and wheel arches contribute 25% to 30% of a vehicle’s total aerodynamic drag ($C_d$).
- Traditional “open-spoke” designs create massive Turbulence inside the arch, which then spills out and disrupts the smooth airflow along the sides of the car.
2. Why EVs Love “Dish” Wheels
For internal combustion engine (ICE) cars, a 3% change in drag might only mean a negligible difference in fuel cost. But for EVs, where every kilowatt-hour counts, aerodynamics is everything.
The Benefits of Aero Wheels:
- Reduced Turbulence: By closing the gaps between spokes, the “Dish” design forces air to slide across the wheel’s surface rather than entering the wheel well.
- Increased Range: Real-world tests (such as on the Tesla Model 3) show that using Aero covers can improve efficiency by 3% to 5% at highway speeds. This can mean an extra 15–20km of range on a single charge.
- Pressure Balancing: Smooth wheel surfaces help maintain high-pressure zones outside the wheel, preventing low-pressure “suction” that pulls the car backward.
3. The Trade-off: Braking and Heat
If closed-off wheels are so efficient, why aren’t all wheels solid discs? The answer is Brake Cooling.
Brakes convert kinetic energy into heat. Without air flowing through the wheels, the brake discs and calipers can’t dissipate heat effectively, leading to Brake Fade (where the brakes lose stopping power).
Modern Aero wheels are a compromise:
- Active Shutter Systems: Some high-end cars have wheels that open or close based on brake temperature.
- Directional Spokes: Many EV wheels use “Turbine” shapes that are aerodynamically efficient while still acting as a pump to pull hot air away from the brakes.
Summary: Form Follows Function
The return of the “Dish” wheel isn’t just a retro fashion statement; it’s a response to the physics of the electric era. As we push for higher efficiency and longer ranges, the “hollowed-out” look of traditional performance wheels is giving way to smooth, integrated aerodynamic surfaces.
If your driving involves a lot of highway cruising, choosing a Low-Drag wheel design is one of the most effective “stealth” upgrades you can make for your vehicle’s efficiency.