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Why drum brakes won’t die KXan 36 Daily News

Drum-type brakes have a number of pros and cons in comparison with more modern and efficient disc mechanisms, however, despite the archaic nature of the scheme, such systems still remain in service. So why don’t disc brakes send their drum counterparts to the dustbin of history?

A drum or friction brake, as you know, brakes due to frictional forces between the inner surface of a rotating drum and fixed brake pads located inside the cylinder. Disc brakes, in contrast, consist of a rotating disc and two fixed pads mounted on either side of the disc inside a caliper. So what is the best system?

Cons of drum mechanisms

At the moment, drum brakes are rapidly losing popularity with automakers for a number of reasons and are used in passenger vehicles mainly on affordable models. One reason is inefficient cooling. When braking from high speeds, drum brakes, due to their closed design, experience severe overheating. Disc brakes, on the other hand, are open and well cooled by air.

At the same time, the drums are not at the height of self-cleaning. If moisture seeps into the drum (rarely, but it happens), then in frost the brake mechanism freezes from the inside and there are problems in order to move the car from its place. The ingress of dirt into the drum is fraught with instability of braking.

Drum brakes are also slower and rougher than disc brakes, due to the instability of the contact patch between the pad and the drum surface. In addition, opening the drum can be a problem – over time, the cover can stick, and many drivers and servicemen remove the brake drum by hitting its outer belt with a hammer, thus risking breaking off part of the part.

It is also true that, as the drums are used, wear products accumulate, simply speaking, metal dust from the pads. When there is a lot of it, the deceleration efficiency will decrease. Therefore, it is necessary to blow out the drum mechanisms with air at every maintenance and even more often. However, progress does not stand still here. Modern designs of “drums” have both improved overheating protection and greater wear resistance than their predecessors.

Wear can be determined through a special hole on the inside of the brake shield. However, in fact, this is not easy to do, and drivers are guided more by the cyclic beat of the brake pedal during braking and the characteristic metallic creak. Meanwhile, when the friction linings reach their minimum thickness, the pads must be changed without delay, as they can leave grooves on the drums and eventually destroy the part.

Advantages of drum mechanisms

What can not be taken away from drum brakes is an impressive resource. The point is the large working surface of the pads, as well as the greater thickness of the working part of the drum. As a result, the pads in the drums go 100 thousand kilometers (on average, two to three times more than disk analogues).

We put the second fat plus on the “drums” for good protection against dirt. Brake pads, springs, hydraulic cylinders and spacer bars are hidden in the drum, as in a kind of wardrobe trunk. As a result, dirt, snow, dust, sand rarely penetrate the drum (unless you skid for hours in a mud rut or sand) and, accordingly, do not affect the performance of the mechanism. Because of this, drum brakes are appreciated by owners who operate their cars in difficult conditions – we are talking primarily about jeepers and all those who move on the crossroads more often than on asphalt.

In addition, we should not forget about the braking potential of drum systems. The closed design makes it possible to make the friction area much larger than that of disk counterparts. And by the way, such a scheme is great for large and heavy vehicles – vans, pickups and minibuses, not to mention trucks and buses.

Another not the most obvious advantage is a simple and reliable combination with the parking brake mechanism. This circumstance, by the way, facilitates the repair and maintenance of the car.

But, perhaps, the main argument why many mass-produced models are still equipped with drums is the ease of production and low cost of maintenance. In particular, since drum brakes do not generate much heat, cheaper consumables are used for them – for example, oil-alcohol-based brake fluids that have a low boiling point.

Drum drum – discord

Note also that modern drum systems are no longer as simple as before, and the main difference between them is the material. At the moment, the choice can be made between aluminum and cast iron versions. The former are thought of as advanced, the latter as “long-playing”, but obsolete.

Parts made of “flying” metal minimize one of the disadvantages of drums – large unsprung masses, which has a positive effect on handling.

In addition, aluminum, unlike cast iron counterparts, does not corrode. As a result, the inner and outer surfaces of such drums remain clean. On the other hand, in comparison with the good old cast iron, aluminum wears out faster and is more susceptible to deformation during temperature changes. In addition, such discs stick even stronger than their cast-iron counterparts, and if you decide to remove such drums, then you cannot do without special “pullers”, otherwise the chances of breaking the part will be great.

Be that as it may, drum brakes on passenger vehicles still live out their lives. Leading automakers have been able to make friends with this type of braking system with ABS and ESP. However, with the active introduction of “smart” stabilization systems, automatic control elements, hybrid technologies and electric drive, work on adapting such electronics to archaic drum mechanisms becomes economically unprofitable.

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