Guide to Mountain Bike Components Levels

road bikes components

SHIMANO components create a more efficient bicycle-to-rider interface that demands less of your energy. We do it through low-effort and precise shifting systems and through linear response braking systems that deliver superior power and modulation. By using components that work for you, you can focus more on the task at hand riding your bicycle.

Components of a Shimano Mountain Bike 


The crankset is what the bicycle pedals attach to and are what your legs spin in circles as you pedal. On modern mountain bikes, the crankset consists of the crank arms, chainrings (the front cogs) and the axle that connects the two crank arms.

The crankset and its number of chainrings dictate how many forward gears a bike has. Modern mountain bikes have one, two or three, with the latest trend being the fewer, the better.

The length of crank arms does vary, but not as much as seen with road bikes. Crank length in mountain biking is typically more standard to help with leverage at an average lower riding speed. With this, smaller bikes will often use 170mm crank arms, with medium-sized bikes and up using a 175mm crank length. Downhill bikes and similar will use shorter 165mm cranks for improved ground clearance.

Bottom bracket

The crankset spins on a set of bearings, these are known as the bottom bracket. The bottom bracket attaches within the frame, and so there is a large array of options to suit various frame designs. The two key types include ones that thread into place (threaded) and ones that are pressed into place and rely on tight tolerances, these are known as ‘press-fit’ bottom brackets.


The cassette is the rear cogs that connect to the rear wheel. These rear cogs dictate how many gears a bike has at the back, with most modern mountain bikes typically offering between eight to twelve gears.


The chain is what connects the front crankset to the rear cassette. Without the chain, the bike has no drive. A chain is usually made of steel and features a series of interconnected links that rotate smoothly but are difficult to twist laterally.


Derailleurs are the components that guide the chain between the cogs. These usually work by having a cable, or hydraulic fluid pull them in one direction and then relying on spring tension within the derailleur to pull the opposite direction. With the rear derailleur made of a series of springs, rough terrain in mountain biking can see this component slap around, often leading to lots of noise and the potential of a dropped chain. In recent years “clutch” equipped rear derailleurs have become the standard for intermediate and better mountain bike derailleurs. This clutch creates a one direction friction in the cage that the chain runs through, and offers a quieter ride with a significantly reduced chance of a dropped chain.

New electronic technology sees small servo motors added to some derailleurs, which control the movement; this is known as electronic shifting. Such technology comes at a premium price but removes the risk of mud, water or general wear affecting shift performance. This is because a cable-operated (mechanical) system relies on precise cable tension and cable condition to accurately move the derailleur between gears.

These are some of the important component levels of a mountain bike.

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