Volkswagen AG VW electric car with technology comeback
14.02.2020
D he aerodynamically optimized rims do their best to hide the technology that is doing its job here. But word has got around in the meantime: The new ID.3, Volkswagen's electrically powered hope, brakes on the rear axle with drums instead of discs. “How out of fashion!”, Many people might say reflexively, after all, this technology is considered out of date and is only used today in a few small cars with little motorization Golf, for example, has been using disc brakes almost exclusively since the fourth generation was launched in 1997 (exceptions with 1.4 and SDI engines and with a convertible roof confirm the rule). So why this technology comeback in a car that is supposed to symbolize progress? You have to go back a bit for an answer, but in summary it can be said: The drum brake is used, BECAUSE - and not ALSO - the ID.3 has an electric drive. container '>
Volkswagen AG
Because of the aerodynamically optimized rims, the drum brakes on the rear axle of the VW ID.3 are barely visible.
Even drivers with combustion engines are familiar with the phenomenon: During the TÜV test or inspection, rust comes to light on the rear windows. The reason: Most of the kinetic energy is dissipated when the vehicle decelerates via the front wheel brakes. The brakes on the rear axle, on the other hand, are rarely used, and the discs corrode as a result. The effect is amplified in an electric car. Especially with an e-mobile like the ID.3, where the motor is on the rear axle. Namely, he drives themnot only on, but also slows it down as soon as it acts as a generator through recuperation and feeds braking energy back into the drive battery. That is why the wheel brakes are only used for comparatively strong maneuvers in everyday life.
The components are protected in the drum
The marketing departments of the electric car manufacturers are taking advantage of this phenomenon ('Lower maintenance costs due to lower brake wear', so the argument). In fact, however, it was found that the windows - especially those on the rear axle - are now increasingly suffering from rust. This means that the brakes no longer work evenly and pulls the car to one side. Because this is relevant to safety, the panes must be replaced; The vehicle owner is usually left with these costs. And as soon as word gets around that rusty brake discs on relatively new cars have to be changed after a short time, this has a negative effect on the reputation of a manufacturer.
Volkswagen is likely to address this curiosity through its experience with the electric models E-Golf and E-Up have discovered the stealth. And after weighing up “costs, weight, necessity and durability”, decided to reactivate the supposedly antiquated technology. In the case of a drum brake, when the pedal is operated, the linings are pressed outwards against the inside of the drum via a spreading mechanism. The wheel is decelerated by the friction because the linings are connected to the wheel suspension via an anchor plate. This works neither better nor worse per se than with a disc brake. The advantage of using the VW ID.3, however, is that the individual components are protected from water, dirt, cold and the like by the drum surrounding them and therefore rust much more slowly.
FACT
For older models - here a Mercedes 190 SL - drum brakes are standard. Are they experiencing a comeback with electric cars?
A lot speaks in favor of drum brakes
But the decision in favor of drum brakes is certainly also based on other criteria. For example, that they are lighter compared to disc brakes.Both the driving dynamics and the range benefit from this. Or that the parking brake can be easily integrated. In addition, it is considered to be less maintenance-intensive because the coverings “glaze” more slowly, i.e. harden with less stress. There is also the environmental aspect: Most of the brake wear remains in the drum, which is why the technology produces less fine dust. However, Volkswagen is likely to see the lower costs of drum brakes compared to disc brakes as the greatest advantage. At least Continental, the supplier of the ID.3 drum stoppers, highlights this in particular.
Of course, drum brakes also have disadvantages. They are only slightly thermally resilient, which is why the braking performance deteriorates more strongly with intensive use - a phenomenon known as fading. On top of that, changing pads and drums is significantly more (time) consuming than with disc brakes. However, these shortcomings are almost negligible because of the advantages mentioned. And for all those who don't trust the thing, let me tell you: the ID.3 also decelerates at the front with normal disc brakes.
