Types and Differences of Disc Brake Rotors
Differences in Rotor Size
The first major difference is rotor size.
The major disc rotors for road bikes are 160mm and 140mm, while larger rotors such as 180mm, 203mm, and 220mm are used for MTB.
Which size rotor to use depends on the rotor size that the disc caliper is compatible with, but most disc brake calipers for road bikes are only compatible with 160mm and 140mm rotors.
The difference between the two rotor sizes is in braking power and weight. The larger the rotor size, the higher the braking power and the better the braking power, but the better the braking power, the more difficult it is to achieve the so-called “hit effect” and the heavier the rotor is. On the other hand, a rotor with a smaller rotor size, such as a 140 mm rotor, is lighter and has less braking force, which makes it easier to apply the braking force.
Differences in Mounting Methods
The disc rotor is mounted on the hub of the wheel, and there are two mounting methods: “6-bolt (6 holes)” and “center lock” proposed by Shimano. In the past, most of them were 6-bolt, but center-lock is now the major method.
The difference between the two methods is the installation method. 6-bolt is installed by tightening six bolts with an Allen wrench, while center-lock is installed by turning the lock ring on the sprocket.
Since they are not interchangeable, a 6-bolt hub requires a 6-bolt rotor and a center-lock hub requires a center-lock rotor. In other words, which mounting method you will use is determined at the time you buy the wheel.
Currently, center-lock is the most common type of hub, so if you are buying a disc wheel now, it is best to choose a wheel with a center-lock hub.
Shimano disc brake rotors are available in “wide” and “narrow” rotor widths, depending on the area of the rotor that is in contact with the caliper pads. Current models of Shimano disc caliper brakes for road bikes and MTBs are basically designed for narrow rotors.
The difference between narrow and wide rotors is the width of the area where the disc caliper pads make contact with the rotor. Basically, narrow rotors are used for narrow-type calipers and wide rotors are used for wide calipers, but some rotors can be used for both narrow and wide calipers.
Shimano disc brake calipers are always marked with the corresponding rotor width, so choose rotors of the corresponding width.
Note that there appears to be no difference in rotor width between Campagnolo and SRAM rotors.
Differences in Compatible Pads
Brake pads installed on disc brake calipers can be broadly classified into two types: metal (metal) and resin (resin). The choice of rotors depends on which type of pad is used.
These days, disc brake calipers are compatible with both metal and resin pads. All rotor sides are compatible with resin, but some rotors are not compatible with metal.
Metal pads have high braking power, as they are used not only on bicycles but also on cars and motorcycles. Resin has lower braking power than metal, but has the advantage of less brake squeal.
Points to consider when selecting a disc rotor
Let’s choose rotors that are compatible with the calipers and wheels.
As we have just seen, the choice of which rotor to choose depends first on which rotors the wheel and caliper are compatible with. Rotor size and width depend on caliper compatibility, while the locking method depends on wheel hub compatibility.
Note that the locking method is simply a difference in mounting method and does not affect the other differences.
If you already have a disc brake road bike, for example, check your bike’s hubs and brakes and choose a compatible rotor.
If you are going to build a disc brake bike, choose the caliper brake wheel you want to use and select a rotor that matches it.
Compatibility of Disc Rotors for Road and MTB
Disc brake rotors for road and MTB use are compatible as long as the four points mentioned earlier (size, width, mounting method, and compatible pads) are the same.
Note, however, that large rotors for MTB, such as 180mm and 200mm, will most likely not work with brake calipers for road bikes.
Disc rotor lineup by manufacturer
Shimano Disc Rotors
Shimano releases disc rotors from different grades for road and MTB, respectively.
The main type is center-lock, but a 6-bolt lineup is also available. The main rotor width is narrow, and wide width rotors are available in both narrow and wide widths.
The higher-end models feature “Ice Technology,” which prevents the rotors from getting too hot. When rotors become hot, they lose friction with the pads, so simply replacing them with Ice Technology rotors can improve their effectiveness.
※○ = Weight undisclosed
Campagnolo Disc Rotors
Campagnolo has two types of disc rotors, both center-locked, 140mm and 160mm in the lineup.
SRAM’s disc rotors
SRAM’s disc rotors are basically available in both 6-bolt and center-lock lines for each model, with the advantage of being able to choose either. The wide range of rotor sizes in the lineup also makes them compatible with most wheels and brakes.
※CENTERLINE ROTOR (6 Bolts) lineup of 140mm, 160mm, 170mm, 180mm, 200mm, 203mm, 220mm