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Comparing mechanical vs. hydraulic disc brakes on eBikes

Comparing mechanical vs. hydraulic disc brakes on eBikes

January 17, 2022 | Justin Christopher

Almost all high-quality eBikes on the market will use disc brakes, and those disc brakes can be one of two common styles - mechanical or hydraulic. While both systems have their merits, it’s worth taking a look at their pros and cons to help you decide.

Shopping for an eBike that uses rim brakes instead of disc brakes? Tread carefully. Electric bicycles need disc brakes because they are heavier, travel faster, and simply need more braking power in order to stop safely. Rim brakes should only be used on casual, low speed eBikes.

What mechanical and hydraulic disc brakes have in common

Mechanical and hydraulic disc brake systems both use a caliper that sits over a steel rotor. When the rider pulls the brake lever, brake pads are forced onto the rotor, creating friction (released as heat) which slows the eBike. The brake pads and rotors are the wear items in the system, and need occasional replacement, regardless of whether they operate in mechanical or hydraulic fashion.

Mechanical disc brakes

On a mechanical disc brake system, the brake lever is connected to the caliper with a steel cable that slides inside a housing (exactly the same as “classic” caliper, cantilever, or V-brakes). The lever pulls the cable while the housing is stationary, which forces the pads to move closer to the rotor.

When the rider releases the lever, a spring in the caliper and return springs in the brake levers move the cable back in the other direction, allowing the pads to retract from the rotor.

Mechanical disc brakes have some key benefits:

  • Less expensive than hydraulic disc systems
  • For home mechanics, mechanical systems can be easier to maintain than hydraulic
  • Fewer specialty tools are required, and what is required is shared with rim brake bikes, so many users already own them
  • No fluid to spill during service
  • Mechanical disc brakes are often maintenance free, or very low maintenance.

Downsides of mechanical disc brakes:

  • While mechanical disc brakes still have plenty of braking power for most riders, it is lower compared with the best hydraulic systems

Hydraulic disc brakes

Hydraulic disc brakes are a higher-end solution and are typically found on more expensive, performance-oriented eBikes - especially mountain bikes ridden on steep, off-road terrain.

In a hydraulic disc brake system, there are no cables. Instead, pulling the lever pushes on a reservoir filled with hydraulic fluid (DOT fluid or mineral oil, depending on the brand/model). The force of the fluid pushes on a piston, with the brake pad sitting on the end of the piston. Releasing the lever returns the piston, and thus the brake pads, to the original position.

Benefits of hydraulic disc brakes include:

  • Best possible ultimate braking power and modulation
  • Less hand fatigue on long descents
  • A very long service interval.
    Hydraulic disc brakes require no maintenance under short intervals in normal conditions, and need the fluid replaced and the system bled very rarely - perhaps years between service, for most riders.

There are some downsides:

  • Specialty tools are required to trim hydraulic lines to length, fill them with fluid, and bleed the system
  • More expensive compared with mechanical systems
It’s possible to build a great eBike with both mechanical and hydraulic brake systems. Your choice should depend on your specific needs and preferences.