: what’s the point of those holes/designs in the middle of car wheels?
In: Engineering
Heat and weight. Brakes generate a lot of heat, and more open wheels allows for increased airflow and heat dissipation/cooling.
Weight is also important, because it’s considered “unsprung weight” which means it’s located below the springs in the suspension. Lighter wheels (less material) provide better handling over uneven pavement.
To help cool the brake rotor/drum. To help reduce rotational weight. To reduce raw material cost. To add to aesthetics.
It’s really that simple.
Mostly weight. You just need enough material connecting the hub to the rim to be strong enough not to break during use. Most are significantly stronger than that minimum so that they can take long term abuse. But even very strong wheel designs don’t need to be even close to solid. And weight reduction on wheels is just about the most important place on the vehicle to do it. Lighter wheels let the suspension react more quickly to bumps so you get a better ride and better handling. It takes less energy to spin a lighter wheel, so a lighter wheel gets you better acceleration, braking, and better fuel economy. And finally, a more open design lets more brake heat out. The brakes are inside the wheels, and the whole point of brakes is to turn motion into heat. So the more heat you can get away from the brakes, the better they work. This is why the best and most expensive wheels will often be very open designs. You can use more expensive forged material which is stronger per weight to make the amount of material connecting the hub to the rotor as small as possible, making the wheel as light and open as it can be.
Beyond what the others have posted, if you look at a fair few of the new electric cars, they come with a plastic Aero cap on their wheel. The design of the wheel (spokes/weight) makes a big difference to their performance, specially at highway speeds.
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