Types of Disc Brakes for Road Bikes

Difference in mechanism

Mechanical (wire) type

Same as conventional caliper brakes and V-brakes, in which an inner wire is pulled by a lever to tighten the caliper that sandwiches the disc rotor. If there is a wire fastening bolt on the disc caliper, it is a mechanical type.

Mechanical disc brakes have the advantages of lower parts prices, the ability to use mechanical STI levers, and easier maintenance. This is probably the reason why mechanical disc brakes are the most common type of low-priced disc road bicycles.

On the other hand, mechanical disc brakes have the disadvantage that the lever pull is heavier than hydraulic disc brakes and it is difficult to perform fine braking, which is a characteristic of disc brakes. Some people even say that caliper brakes work better than mechanical disc brakes.

In Shimano’s road-use disc brakes, only the SORA grade is available as a mechanical type, and there is also the disadvantage of not being able to select higher grade brakes.

Hydraulic

The current mainstream of higher grade disc road bikes is hydraulic.

In contrast to the mechanical type, where braking is adjusted by the amount of wire pulled, the caliper is closed by the pressure of oil between the brake and the lever, making it easy to make fine adjustments and very light to pull. In expensive models, it is so light that it can be popped with a single pinky finger.

The disadvantages of the hydraulic type are the cost of parts and the time and effort required for maintenance. Air bleed is necessary to generate pressure, and every time the oil hose is replaced, the oil needs to be changed and the air needs to be bleed out.

In addition, since the hoses are basically installed in the frame, handlebars, and fork to protect them from the outside, there is little play in the hoses, and in some cases the hoses cannot be removed without disconnecting them when performing maintenance around the handlebars, such as when replacing the handlebars or stem.

All Shimano road disc brakes, TIAGRA and above, are hydraulic.

Disc Rotor Differences

Size Differences

There are different sizes of disc rotors, such as 140mm and 160mm. Basically, the larger the size, the greater the braking power, but the heavier the pull and the harder it is to perform fine braking.

In addition, disc brakes tend to heat up more than caliper brakes, which sandwich the rim, but the larger the rotor size, the more effective it is at dissipating heat.

Differences in Mounting Standards

There are several mounting standards for disc rotors.

The two main types are as follows

1. center lock
2. 6-bolt

Which one you choose depends on what the mounting standard is for the wheel you have.

The difference is that the 6-bolt type usually uses a tool to tighten the bolt, while the center-lock type uses a lock ring remover used to tighten the sprocket to tighten the rotor.

Shaft Difference

Through Axle

The current type is the through-axle. The shaft is thicker than the conventional quick release, and since it is tightened using a tool, it is more rigid and produces more stable braking force.

Unlike quick releases, the tightening is constant, so there is less chance of the rotor making noise due to incorrect tightening.

Installation requires a frame and fork that are compatible with through axles, and current disc brake wheels for road bikes are usually equipped with a 142mm rear-end through axle.

Quick Release

The main type of wheel that was used in the days when there were few through-axle frames and forks was the quick-release type, the same as the conventional wheel for rim brakes. It has the advantage of simple construction and quick detachment.

Another advantage for those who are thinking of upgrading to a caliper brake type frame is the ability to use disc brakes on a frame that is not through-axle compatible, since the ends are not through-axle compatible.

However, since most disc brake-compatible wheels are now through-axle, there are very few in circulation, not only new but also used.

The front wheel can replace a rim brake wheel because the front wheel is almost always 100mm, but the rear end width is often 135mm instead of the 130mm commonly used on rim brake wheels, so the frame side must also have a 135mm end width.