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I am planning to buy a two wheeler and wanted to know which of the two brakes is better, in order to take an informed decision.

Thanks!

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Disc brakes are way better. They have no self-servo effect like drum brakes. In disc brakes, the braking force is linearly dependent on the brake application force and also on the coefficient of friction.

In contrast, on drum brakes, extremely small variations of coefficient of friction can mean huge differences in braking force. Usually, the drum brakes are not exposed to elements, but if you manage to get some water somehow there, it can be harmful. Furthermore, the braking force is not a linear function of the brake application force.

Choose discs! There is no reason to choose drum brakes unless the self-servo effect is mandatory for a reasonable braking force, like it is on big rigs. Especially on a two-wheeler, I would prefer disc brakes, because the ability to control braking force on two-wheelers is more important than on cars.

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    Disc brakes also spin off any water that might collect on them. And since the pad generally only contacts a small portion of the disc, the disc has time to cool off before the same area passes between the pads again. In drum brakes, the only way the drum cools is by conduction and radiation through the drum material. – BillDOe Apr 16 '18 at 19:14
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    Disk brakes are also easier to replace. Pads can often be popped out and in with one tool, while drum brakes are time consuming at best. – fred_dot_u Apr 16 '18 at 20:12
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    Do you think the using the term "catastrophic" to describe when drum brakes gets wet is a bit over the top? Drum brakes have been used for a long time. I can guarantee you every single application on the road today gets some amount of water in them from time to time. They continue to work. Maybe you are being specific to motorcycles, but really, from my point of view there is nothing catastrophic about it if they get wet. – Pᴀᴜʟsᴛᴇʀ2 Apr 16 '18 at 20:22
  • Depends on how much water gets trapped in the drum. – Moab Apr 16 '18 at 23:33
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The primary faults of drum brakes are they need to be adjusted on a regular interval and brake fade. As the brake shoe material wears the distance between the drum braking surface and the brake shoe increases. Hence the need for mechanical readjustment. Disc brakes are self adjusting. The fade issue appears as the drum gets hot from the friction of the brake shoe. As the drum get hot it expands. This increases the distance between the shoe and the drums' braking surface. This means additional pedal/lever pressure to achieve the same braking force.

  • On autos I would agree but we are discussing two wheelers. The self adjusters usually the result of on some other action, such as using the park brake or stopping quickly while in reverse. Neither of which is applicable on a motorbike. – mikes Apr 17 '18 at 10:06
  • There are nany drum brakes that are self-adjusting : with the spring, tooth and cam arrangement... – Solar Mike Apr 17 '18 at 17:00

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