What’s a modern day mountain bike without a groupset? Well, it’s a frame, suspension fork, wheels and control items, but it’s not a bike. Thought of as the bike’s engine room, the drivetrain consists of the cranks, chainring/s (front cogs), chain, cassette (rear cogs), derailleurs and shifters. Simply put, it’s a closed circuit that propels the bike forwards.
As you spend more money, the efficiency, durability and shifting performance increases while the weight decreases. In this article, you’ll learn what you need to know when it comes to mountain bike groupsets including what each part does, the key difference between various price points and other information you’ll need to make an educated decision on which groupset is best for you
Components of a groupset
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 together.
The crankset and its number of chainrings dictate how many front 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.
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.