How do bicycle disc brake rotor work – detailed explained

How do bicycle disc brake rotor work - detailed explained

Disc brake rotors are bicycle components mounted on the wheel hub to provide braking power in a disc brake system. You can also check the top 10 bike brakes brands in the world for your reference.

Disc brake rotor comes in a variety of sizes to suit different terrains and riding habits.

The simplest brake rotor is made of stamped stainless steel, while the more expensive ones have complex internal structures to improve braking performance and reduce weight.

There are two common types of rotor mounting – center-lock and six-bolt.

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    What are disc brake rotors?

    Disc brake rotors are metal discs mounted on a hub and are the primary contact surface for braking the clamp.

    Different sizes and designs can be used for different purposes, some prioritizing maximum braking force, others prioritizing generating the least amount of heat, and, of course, some are designed for weight reduction.

    What are disc brake rotors

    How do bicycle discs brake rotor work?

    The working principle of the bicycle disc brake rotor is to reduce the speed of the bicycle through friction to complete the braking action. 

    When braking, the two pads clamp the rotor to achieve braking, and when not braking, it will automatically return to the position.

    The rotor works by slowing the rotation of the wheelset, using clamping calipers to squeeze the disc brake rotor to create friction. What are the differences between disc brake vs. rim brake?

    This generates heat. The larger the brake rotor, the more heat is absorbed by it, and the smaller the brake rotor, the easier it is to overheat, resulting in heat exhaustion and a significant drop in braking power or even disappearance.

    Simply put, the larger the rotor, the better the braking. However, not all vehicles and riders need maximum braking power, and in many cases it is important to find the right balance between braking power, braking feel and light weight.

    How do bicycle discs brake rotor work

    What is the difference in disc brake rotor size?

    Bicycle disc brake rotor is usually divided into 140mm, 160mm, 180mm, 203mm, 220mm diameter, road bike hydraulic brakes are mostly 140mm and 160mm rotor.

    Considering that mountain bikes need more braking power and tires can also provide more grip, so the rotor size usually starts at 160mm.

    The current mainstream trend is to use larger 180mm or even 203mm (200mm) disc brake rotor on the front wheel of XC mountain bikes to further increase braking power.

    Generally speaking, the larger the rotor, the longer the power arm is when braking, and the greater the braking force, the more energy-saving it is.

    What is the difference in disc brake rotor size

    With the current trend, there is no doubt that a larger disc brake rotor can bring more braking power. All other things being equal, more braking power can be achieved simply by increasing the rotor size.

    This is because a larger rotor allows the brakes to obtain a larger brake force arm, or brake radius.

    Generally, road bikes and cyclocross bikes use disc brake rotors of 140-160 mm, which are not only suitable for braking power but also lightweight; mountain bikes generally use rotors of 180-220 mm. You can also check the top 10 road bike groupsets manufacturers in the world for your reference.

    Many mountain bikes have a “big front, small rear” configuration, such as 200mm brake rotor in the front and 180mm in the rear; today’s downhill bikes also use 200mm rotor or more, as do e-bikes.

    What are the benefits of a thicker disc brake rotor?

    What are the benefits of a thicker disc brake rotor

    Disc brake rotor design and material

    Most disc brake rotors are made of high quality stainless steel, which not only provides a strong and durable braking surface, but is also usable all day long.

    The rotor has many cutouts that help water, mud, and small debris come off quickly.

    These designed and properly lined holes also provide weight reduction.

    One of the major design requirements of a rotor is heat dissipation, and there are many ways to achieve this claim.

    Some disc brake rotors are coated with heat dissipating material on the inner rim, some are made thicker to dissipate heat like SRAM’s latest mountain rotor.

    And some are made like motorcycle disc brake rotors with a stainless steel outer rim attached to an aluminum inner rim.

    This design claims to speed up heat dissipation while being lighter in weight, while Shimano’s IceTech sandwichs a thin layer of aluminum between two pieces of stainless steel to speed up heat dissipation.

    Disc brake rotor design and material

    Installation standard: center lock vs. six bolts

    For braking to be strong, the mounting must be secure. The two common ways of mounting the rotor are center-lock and six bolts.

    The most common is the latter, where the disc brake rotor is screwed onto the hub through six bolts, which is not only lightweight but also simple enough to construct with your hands.

    Then there’s the center lock, where the rotor first slides onto the hub in a specific position, and then the screw cap is screwed on, and a specific tool is used here.

    Installation standard - center lock vs. six bolts

    How do I install a disc brake rotor?

    Take a six-bolt rotor, for example. It needs to be mounted using the butt-lock method.

    Otherwise, it will cause the rotor to deflect and make ear-splitting noise. Generally, there is a standard installation torque value for rotor. If there is no standard, it can be installed according to 6N.m.

    The direction of the arrow on the disc brake rotor should be the same as the rolling direction of the bike tires. Wrong direction will damage or deform the rotor.

    How do I install a disc brake rotor

    How often do you change the disc brake rotors?

    Like the disc brake pad, the rotor is a consumable part. Every time you squeeze the brakes will lose a little bit, over the years it will need to be replaced.

    Judging the timing of the replacement sign is the thickness of the rotor, Shimano recommended 1.8 mm thick disc if worn not to get 1.5 mm then hurry to change;

    SRAM is recommended to wear more than 0.3 mm then hurry to change, or the thickness has been less than the amount of disc surface labeling.

    How often do you change the disc brake rotors

    How do I take care of my discs brake rotor?

    1. Many disc brake rotors are made of stainless steel. When the disc brake rotor is oiled, you can simply use isopropyl alcohol or alcohol wipe for cleaning. 
    2. High temperatures can be generated by braking the  rotor on long descents, so do not pour water directly over them to cool them down. This will lead to rotor deformation, loss of rigidity and loss of braking power. 
    3. Disc brake rotors of different sizes need to be replaced at different wear levels: 1.8mm disc brake rotors need to be replaced when worn to less than 1.5mm; 2.3mm rotors need to be replaced when worn to less than 1.9mm. 
    4. In order to visualize when the rotor needs to be replaced, you can purchase a rotor with wear warning points. When the rotor is worn to the black warning points, the black coating will be worn away, indicating that the rotor needs to be replaced. 
    5. Wipe it regularly to prolong its life. (Do not use water to wipe, water may cause the rotor to rust) 
    6. Never touch the rotor with your hand after riding, it will burn. 
    7. Disc brake rotors and pads need to break in for a while, don’t put on a new one and have a sharp brake.

    How do I take care of my discs brake rotor

    How do I know which disc brake rotor to buy?

    There are a couple of things to keep in mind when buying disc brake rotor:

    1. Buy the same brand of rotor as your clamps, unless you are making special modifications; 
    2. Buy the type of brake rotor that your wheelset is compatible with, and see if it’s a center-lock or a six-bolt. 
    3. Look at the frame and fork to see what size brake rotor will fit; 
    4. See how much braking power you need. If you’ve had trouble braking before, buy a bigger one this time.

    For more consultation about bike or e-bike, you can also contact us – your bike solutions expert – SAMEBIKE.

    How do I know which disc brake rotor to buy

    Hi, I'm an experienced writer about mechanic and an expert on bike and e-bike tech who appreciates practical, beautifully-engineered things. And of course, I love cycling.
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