Hydraulic and Mechanical Disc Brakes Compared

Not sure which kind of disc brake your bike has? Look at what runs from the brake lever to the caliper. That one check answers most of the question.

How to tell which one you have

Park Tool puts the difference simply. A mechanical brake uses a cable. A hydraulic one uses fluid in a hose.¹

So follow the line from the lever:

• A cable running through housing points to a mechanical brake. The housing can be lengthened or shortened with a barrel adjuster, a twist-to-adjust fitting that may be at the lever, the caliper or both.¹
• A hose that carries fluid points to a hydraulic brake.¹
• A cable that looks mechanical but behaves like fluid. Park Tool notes a case where "Even though there is a cable, the internals are hydraulic."² If the caliper is unclear, check the maker's manual for your model.

What's different in use

Wikipedia says there are two main types of disc brake, mechanical (cable-actuated) and hydraulic.³ It adds that the pros and cons are "highly discussed" by users. The usual claims are that cable brakes cost less, need less maintenance and weigh less, and that hydraulic brakes are said to offer more braking power and better control.³ Those are arguments, not measurements, so treat them as such.

A table helps to keep the practical differences in one place.

Care that depends on the type

Mechanical. As pads wear, the gap grows. Park Tool warns: "Do not use the barrel adjuster to move the pads inward as they wear."¹ The adjuster is for taking up cable slack. The caliper has its own pad adjusters for wear. Your manual will show which is which.

Hydraulic. Wikipedia notes that some hydraulic brakes, especially older ones, have manual gap controls, while many are self-adjusting.³ There's one habit to keep in mind. Park Tool warns that if you squeeze the lever with the wheel removed, the pistons will come back out.² Follow your manual when the wheel is off.

Fluid work, such as bleeding, belongs in the manual for your exact brake. Fluid types and bleeding are planned for a later page on this site.

One arm or two

Park Tool says most mechanical calipers have one lever arm that moves only the outer pad. The rotor then flexes over to meet the inner pad. Some designs have two lever arms, and on those both pads move evenly toward the rotor.¹ Wikipedia describes the same split for disc brakes in general: some move both pads, and some move one.³

When you check pads, look at both of them. Don't judge by the one you can see.

Which one does a given e-bike have?

The type of bike won't tell you. Check the lever and caliper, as above, or the spec sheet or manual that came with your bike. With a secondhand bike and no paperwork, the maker's support page for the brake model is the next place to look.