Main Components of a Mountain Bike: How to Choose the Right Parts for Your Ride

The bicycle, and specifically the mountain bike, is relatively simple as a device, but on the other hand, modern technologies, various riding styles, and the narrower specialization of individual models lead to different standards, technical solutions, and options for each of its components. Before we examine these details in separate articles, it is good to know in general what the main components of a mountain bike are and what the most important things about them are.

Frame

Undoubtedly, this is the foundation of every mountain bike and therefore the most important part of it. Frames come in different types according to various criteria: hardtail or full suspension; for one or another type of riding (XC, AM/enduro, DH/FR, etc.); made from different materials (aluminum, carbon, steel, titanium, etc.) and so on. These and other characteristics (mainly geometry, but also wheel size, strength, weight, etc.) are directly related to the purpose of the frame and thus the entire bike.

When choosing a frame, it is important to know what type of riding it is needed for and what the correct size for us is. If the frame does not meet these basic requirements, it will be difficult to feel the bike as our own; something will always seem off. From there, depending on the budget we have set aside, we can choose whether the frame should be hardtail or full suspension, how light it should be, and what additional features it should have.

For frames with suspension, the rear shock absorber is considered a separate component, although its characteristics are often directly dependent on the frame and its purpose.

Fork

At one end of the fork, the front wheel is attached; at the other, the handlebar. Between these two points, the fork contacts the frame through the steerer tube and headset bearings (cups).

Almost without exception, modern mountain bikes have a suspension fork that absorbs vibrations from rough terrain. There are also mountain bikes with rigid forks, but these are more of an exotic or narrowly specialized option.

Suspension forks have various characteristics such as travel length, internal design, external adjustments, materials used, and so on. Their price is usually directly related to these features.

When choosing a suspension fork, it is first important to know its intended use and whether it corresponds to the type of riding we plan to do. Within these limits, the more expensive the fork, the lighter, more advanced, and with more adjustment options it is. For complete bikes, the manufacturer usually selects the fork according to the bike’s price and purpose.

Wheels

A complex component made up of several others. This is one of the most important parts of the bike, which has also given it its common name "wheel".

The wheels of a mountain bike are laced from rims, spokes, and hubs. Tires are mounted on the rims, and brake discs on the hubs. The cassette is mounted on the rear hub.

The weight of the wheels (including tires) is of exceptional importance for the bike’s behavior and feel. The lower the weight, the easier the wheels spin, meaning the bike accelerates faster and moves more easily. On the other hand, mountain bike wheels must also be strong and resistant to twisting, so manufacturers and users always seek a balance between these characteristics considering the bike’s purpose and price.

Today, three wheel sizes are offered on the market for mountain bikes – 26 inches (the oldest), 29 inches (the largest), and 27.5 inches (the newest, intermediate standard). Each has certain features and its own advantages and disadvantages. The wheel size is predetermined by the frame, i.e., it is designed for one of these three standards.

Drivetrain

This term includes a whole group of components that allow the bike to be powered by human force. These are the chain, front and rear sprockets, derailleurs, shifters, cranks with bottom bracket, and pedals.

Cranks (plural, because there are two, left and right) are the main component to which the front chainrings (gears, on the right side) and pedals are attached. Simply put, these are two levers mounted to the frame via the bottom bracket (the so-called axle-cassette), through which the force applied by the feet is converted into rotational motion. Through the chain, this motion is transmitted to the rear sprockets (cassette).

Usually, there are 1, 2, or 3 chainrings in front, and from 6 to 12 sprockets in the rear of different sizes. This combination determines the number of gears (the number of front chainrings multiplied by the number of rear sprockets). It is good to know that a larger chainring in front means a higher (harder) gear, while in the rear it is the opposite – larger sprockets provide lower gears.

To change gears, the chain must be moved to a larger or smaller chainring in front or rear. This is done by the derailleurs – front and rear – after a command is given from the handlebar. That is why the handlebar shifters are called shifters.

All components of the gear system must conform to the same standard to work correctly. Shifters and derailleurs are usually compatible with a specific number of chainrings in front and sprockets in the rear, as well as other features such as maximum gear size, type of frame attachment, and more.

Brakes

It is unnecessary to explain what brakes do, but it should be noted that most modern mountain bikes, even in the entry price class, use disc brakes. Most often, these are hydraulic – using fluid and a pump to amplify and transfer the force applied by the hand through the brake lever to the pistons with pads that press the disc. However, cheaper bikes may have mechanical disc brakes, which rely on a cable.

As with other components, many brake characteristics depend on price – weight, materials, adjustment options, and more. Although most brakes are not narrowly specialized for a specific type of riding, there are models that emphasize low weight and others that focus on maximum braking power. All else being equal, the latter also depends on the size of the disc (also called rotor, although strictly speaking and terminologically, this is not entirely correct).

Peripheral Components

This group includes the handlebar, stem, grips, seatpost, and saddle. Although these components are relatively simple devices, they are extremely important for the comfort and overall feel of the mountain bike. Therefore, very often when buying a new bike, a person needs to replace some of them to achieve maximum comfort according to their individual needs. Here are a few important things you should know about them:
A wider (or longer, depending on perspective) handlebar increases the bike’s stability but somewhat reduces maneuverability. Additionally, taller riders are recommended to use wider handlebars.

The length of the stem results in more or less leaning of the body toward the handlebar and more or less weight concentrated on the front wheel. Also, a shorter stem makes steering and turning quicker and more direct, while a longer one slows them down. Usually, for XC riding, a stem length of 70-100 mm is recommended, while for AM/enduro/DH/FR, a shorter stem of 40-60 mm is preferred. For tall riders, a slightly longer stem is generally recommended.

Choosing a saddle that is maximally comfortable is difficult, sometimes requiring several trials and errors. This choice is strictly individual – some prefer softer and wider saddles, others narrower and firmer. Width usually depends entirely on the person’s anatomy, i.e., how wide their sit bones are, which must bear most of the body’s weight. Firmness is usually chosen according to riding intensity – for sporty riding and longer time on the saddle, a firmer one is generally recommended.

Thanks to Lyubomir Botusharov from mtb.bg for the presentation