The crankset is a vital component of a bike. It is also known as the chainset. This is what enables your bike to change gears.
It is made up of 2 parts, the crank arms, and bottom bracket. Chainrings are not technically part of the crankset but are vital to its function.
They come in 3 main forms too - single, double, and triple.
What type of crankset you need will vary depending on the type of bike you are riding and the terrain you will be riding on.
For cyclists that race on the road and those who do mountain bike riding, you will be looking for lightweight cranksets. People who cycle as a hobby will be looking for more durable cranksets that are protected from the elements and have long-lasting chainrings.
BMX riders need incredibly strong cranksets due to all the blunt force trauma the bike will be under during their stunts. Gravity riders will need a combination of being lightweight, strong, and durable.
Crank arms
There are 2 of these on either side of the crank. They are connected by an axle and are positioned opposite each other. The pedals are then attached to the empty ends of the crank arms.
These are made from lots of materials, but the most common are aluminum, steel, and carbon fiber. Carbon fiber is the most costly of the materials and is only really found on racing bikes, whether they be on- or off-road.
You generally find steel cranks on BMX and older bike models, whereas aluminum is common on low- to mid-range road and mountain bikes.
Bottom bracket
This is made up of a rotating axle contained within many sets of bearings. These should be sealed from the elements to make them more durable. The older models of bottom brackets are called cartridges. In cartridge brackets the axle and bearings are inside a single tube which can be replaced as necessary.
Modern bottom brackets are known as external brackets. In these, there are larger bearings located near the end of the axle, outside the frame. This style of bracket is better as you get more stiffness and less weight on your bike.
If you are changing from a cartridge to an external bottom bracket it is a good idea to get the shell faced by a professional. When something is faced, the opposing edges are ground down to ensure the bearings are perfectly lined up.
Chainrings
This is the part of the bike where the chain rests. They tend to be constructed from steel or lightweight aluminum alloy. They have spokes to allow the spaces in the chain rest and not fall off.
There are a varying number of chainrings depending on the size and type of your bike. Road and mountain bikes have anywhere between 1 and 3 , whereas BMX bikes tend to only have one.
The chainrings are what allow you to change gears when riding. They are bolted to a 4 or 5 arm spider (a piece of metal that attaches to the frame of the bike).
How to remove a crankset
You will need
- 15mm wrench
- Screwdriver
- Allen key (usually 4-8mm)
- Crank extractor tool (if non-self-extracting)
Instructions
The first step to removing the crankset is to take off the pedals. For this you will need your wrench. Start with the right pedal as the left is reverse-threaded.
Place the wrench around the area where the crank arm and pedal connect. You will need to turn the wrench in a counterclockwise direction. It will take 2 to 3 turns to loosen the pedal from the crank arm. You will know when to stop as the pedal will rotate easily without stopping.
You will now need to grab the pedal and turn the crank arm in the opposite direction, clockwise. Keep turning it until the pedal has come off of the arm. This can take anywhere between 10 and 30 full turns to remove. You will physically feel the pedal unthreading.
For the left pedal you will need to use the wrench to loosen it from the bike’s body. If you are standing on the right side of the bike, turn the crank arm clockwise to detach it from the bike. If you are standing on the left, counterclockwise.
Set the pedals aside for now.
Look to see whether your crank has a cap in the center. Use your screwdriver to pop this cap off to show the crank bolt. This is hexagonal in shape and will fit an Allen key.
Check if your crank has pinch bolts. These are smaller bolts at the top that will fit a 5mm Allen key. Rotate counterclockwise to allow the crank arm to be detached from the crankset. These are primarily found in Shimano cranks. You will also need to look on the left side of the bike and unscrew the plastic preload screw there.
Select the correct size of Allen key - it should fit snugly in the hole and the crank bolt should turn with it. Rotate counterclockwise until the crank bolt is out. Some models of bikes have bolts on both sides of the bike. If this is the case, both must be removed.
If there is only a single crank bolt with a ring around it on one side of your bike, you have self-extracting cranks. You will not need a crank extractor tool to remove these.
Slip the crank off of the spindle. Pull the crank arm away from the bike to detach it from the crankset. Pull the other side of the crank from the bottom bracket. Pull the remaining crank away from the bike and remove from the bottom bracket.
If you have non-self-extracting cranks you will need to use the crank extractor to loosen them. Place the end of the crank extractor inside the bolt hole and rotate clockwise to secure. Rotate the extractor handle in the opposite direction until the crank pops off. Repeat on the other side.