Electric cars are at the top when it comes to technological developments, but they are often equipped with strange ‘closed’ rims and sometimes even old-fashioned drum brakes. How did that happen?
The future of cars in Europe is electric, as the European Court of Auditors confirmed again this week: there is no future for combustion engines and so we will all drive electric in the coming decades. For many motorists, the often limited range is a problem and so manufacturers try to squeeze as many kilometers out of the cars as possible. They do this not only by installing the best possible batteries, but also by increasing aerodynamics.
Closed wheels of a time trial bicycle
One of the ways to do this is to install a closed grille, a completely flat underbody and wheels that are as smooth as possible – and therefore often completely closed. The same principle applies to the rims as to so-called time trial bicycles in cycling. Here too, the wheels are ultra-light and completely closed to prevent the openings from creating turbulence. All these elements contribute to improving the air resistance coefficient, or Cd value.
With the right rims, electric cars can add quite a few kilometers to their driving range. On the one hand by being lighter, on the other hand with the help of an aerodynamic shape. Because the better you cut through the air, the less energy you have to use to maintain a certain speed and the more efficiently you drive. And then those somewhat strange rims come in handy. Especially when you know that almost 25 percent of a car’s aerodynamic drag is directly or indirectly caused by the rims.
About 10 kilometers extra
BMW calculated what the special wheels of the iX3 do for the driving range of this SUV. The improved aerodynamics and lower weight of the wheels reduce the power consumption of this model by 2 percent. According to BMW, this equates to an energy saving of 0.4 kWh/100 km, or 10 kilometers of extra driving range compared to an iX3 with standard rims.
The German electric car rental company NextMove did a test on the Autobahn at 150 km/h with the Tesla Model 3. The aerodynamic wheels turned out to be good for 8 kilometers more range. That’s a difference of 3 percent. With its latest electric model, the Q4 e-tron, Audi speaks of a gain of 5 kilometers on a full charge if you choose the model with the aerodynamic rims.
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Is this all worth it?
You may of course wonder whether it is worth it: all that research for an extra 10 kilometers. This rarely happens for fuel-powered cars, which you can fill up in five minutes. But in the world of electric cars, those extra miles compared to the competition can be the final push to convince a potential buyer.
Drum brakes
Also special is the return of drum brakes on electric cars. Until recently, these were only applied to small cars and budget models. However, electric cars are increasingly being equipped with drum brakes and this is because brakes are used much less in electric cars.
Electric cars largely brake by recuperating braking energy. This energy is generated by a generator and the battery is refilled. Due to this recovery, the classic brake is used less and less in everyday life. With the right driving style, up to 95 percent of your car’s deceleration is absorbed by the regenerative braking system. That’s good for your battery, but bad for the brake discs.
Rust causes danger
When your car has been in the rain for a few days, a small layer of rust can often be seen on your brake discs. This normally goes away when you brake a few times, except for electric cars. This layer of rust continues to build up and in extreme cases can even lead to failure of the braking system. Drum brakes do not suffer from this, because unlike the ‘open’ discs that are optimized for cooling, the brake drum is a closed system that is considerably less sensitive to water and dirt.
Drum brakes: less particulate matter
In electric cars, drum brakes lead to more durable and reliable brakes. Compared to disc brakes, drum brakes also score well when it comes to particulate matter pollution: where disc brakes throw away the brake dust unfiltered, the closed drum brake system has a collection container that can be emptied during inspections. This is very important, since brake pads, tires and wear of the road surface directly contribute to more than half of the total particulate matter pollution.
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Tags: Oldfashioned drum brakes modern electric cars rust chance advantage Car
