A bike cassette is a group of gears located at the back of a bike, and it is used to change the speed and distance traveled. The procedure for removing this cassette is not difficult and does not require much-specialized knowledge.
Some cyclists may not know what a bike cassette is or why they need to perform this procedure, so we will talk about these topics before we get started with the removal process.
- What are Cogs Or Sprockets?
- When To Replace The Rear Cogs?
- Identifying Freehubs Vs. Freewheels
- Cassette Sprocket Removal And Installation
- Freewheel Removal And Installation
- Sprocket Inspection And Cleaning
What are Cogs Or Sprockets?
The rear sprockets – or cogs, as they are sometimes called – are the gears mounted to the rear wheel of the bike. The sprocket teeth engage with the chain and propel the bicycle forward.
The gear ratio of the bicycle’s drive system is defined by the number of teeth on the cog combined with the number of teeth on the chainring. The number of teeth is usually stamped on the side of the cogs or chainrings so you don’t have to count them to determine the size.
The higher the number of cog and chainring combinations, the more gear ratios are available and the greater the range of terrains on which you may ride.
Over time, the chain will begin to slip or skip on a cog when pedaling hard, this indicates that the cog or cogs may be worn out and must be replaced.
When To Replace The Rear Cogs?
There are two reasons to replace the rear cassette cogs. One is because the cogs are worn out. The other reason is to get a different gear ratio by changing the cogs with more or fewer teeth.
Let’s talk about the first since it is probably the main reason why it needs to be replaced.
The cogs wear due to the chain’s rubbing against their teeth. If a cog is worn out, you’ll know it when you ride on it. When you put a lot of stress on the pedals, such as when accelerating or climbing, the chain will skip over the worn teeth of that cog. You can easily feel and hear this when it happens.
Usually, the smaller the cog size, the quicker the wear because there are fewer teeth to distribute the load. If your cog or cogs have worn down to the point that they cause drivetrain skipping, you’ll need to replace the entire cogset and the chain.
Identifying Freehubs Vs. Freewheels
Modern bikes have a ratcheting mechanism and cogs that connect the rear sprockets to the pedals via the chain and allow you to coast when you stop pedaling. The rear sprockets on multi-speed bikes are attached to the hub in one of two ways – the freehub system and the freewheel system.
The freehub system or cassette system is a cylindrical mechanism that has a body with a series of splines on the outer shell. The sprockets mate to these splines and are secured to the hub body with a lockring. When the sprockets are removed, the ratcheting freehub remains on the hub body.
Most modern derailleur bikes use the freehub system and can be found on some single-speeds as well as 6-, 7-, 8-, 9-, 10- and 11-speed rear sprocket systems.
An alternative system is the freewheel. Freewheels are available with single or multiple cogs, up to nine speeds. Freewheels thread on and off the hub. The standard size for freewheels is 1.37 inch x 24 tpi. The sprockets with the ratcheting mechanism can be removed from the hub, cleaned, and reinstalled as a unit.
Freewheels are made of two assemblies – The outer body with the cogs will freely rotate counter-clockwise for coasting. The inner body is made up of the threads that attach to the hub. The inner body should have notches or splines to match the removal tool, which is usually recessed inside the smallest sprocket.
Cassette Sprocket Removal And Installation
Replacing the cassette sprocket is not particularly difficult, but you do need the appropriate tools.
Tools To Remove Bike Cassette
For modern Shimano, SRAM, and Campagnolo cassettes, it requires a chain whip, a cassette lockring remover, and a large adjustable wrench.
For old cassettes without lockrings, you’ll need two chain whips to remove the cassette.
Procedure for Cassette Removal
Below are the procedure for cassette sprocket removal:
- Mount the bike on the repair stand and remove the rear wheel from the bike
- Unscrew the quick-release mechanism or the axle nut, and insert the cassette lockring remover into the spline
- For extra stability, reinstall the quick-release (remove the springs first) to hold the remover in place
- Stand the wheel up (hold it or lean it against something), and wrap the chain section of a chain whip around the largest cog, placing the handle forward (in the drive direction).
- Then place a large adjustable wrench on the flats of the lockring remover with the handle facing the other direction.
- Hold the sprockets from rotating in the counter-clockwise direction with the chain whip tool while turning the lockring remover counter-clockwise with the adjustable wrench.
- Once loose, turn the lockring remover one full revolution counter-clockwise.
- Remove the quick-release mechanism before continuing to remove the lockring.
- Continue to hold the sprockets and turn remover counter-clockwise until the lockring is removed from the freehub.
- Once the lockring is removed, the cogs will slide off the hub. Note the orientation of spacers behind the sprockets. It should be replaced in the same order as it was removed.
Procedure for Cassette Installation
Below are the procedure for cassette sprocket installation:
- Inspect and grease the splines of the freehub body and look for the wide space between the splines.
- Inspect the internal splines of the sprockets and look for the wide spline.
- Align the wide spline of the sprockets with the wide space on the freehub.
- Grease the threads on the lockring and thread the lockring into the freehub body
- Insert the cassette lockring tool into the splines of the lockring.
- Install the quick-release skewer and thread the skewer nut on the outside of the lockring tool.
- Secure the skewer nut against the lockring remover
- Turn the cassette lockring tool clockwise until the lockring is fully tightened.
Freewheel Removal And Installation
There have been numerous types and brands of freewheels throughout the years, and some don’t even come with a tool. To remove the freewheel, first, figure out the type or brand and the appropriate removal tool. The removal tool must fit the part correctly, or both may become damaged.
To determine the type or brand of freewheel, remove the wheel from the bike and look at the flat surfaces of the freewheel near the axle for a brand name.
Tools To Remove Freewheel
To remove a freewheel, you will need a freewheel removal tool. These tools fit into the special notches or splines on the freewheel to enable it to be removed.
Almost every type of freewheel requires a different tool, one made especially for it. It is important to use the correct tool to remove the freewheel, but if the wrong tool is used, you can damage the freewheel.
In addition to the freewheel removal tool, you’ll need a large adjustable wrench
Procedure for Freewheel Removal
Below are the procedure for freewheel removal:
- Mount bike on repair stand and remove the rear wheel
- Remove the quick-release skewer or the drive side axle nut
- Inspect the freewheel center and select the correct type of remover
- Engage the remover onto the splined notches on the freewheel and re-Install the quick-release skewer nut. The skewer nut should be on the outside of the remover.
- Snug the skewer nut or axle nut against the remover. The nut should act as the holding device for the remover.
- Turn the remover counter-clockwise using a large adjustable wrench
- Turn the remover only one full revolution counter-clockwise
- Loosen and remove the skewer or axle nut before continuing to remove the freewheel
- Turn the remover counter-clockwise until freewheel is unthreaded from the hub
- Lift the freewheel from the hub
Procedure for Freewheel Installation
Below are the procedure for freewheel installation:
- Apply grease heavily inside the mounting threads of freewheel
- Lay the wheel on the bench and hold it flat. Hold the freewheel sprockets parallel to the wheel and the lower freewheel onto the threads
- The axle should be centered in the hold of the freewheel
- Begin the threading freewheel clockwise by hand until the freewheel feels fully threaded
- Use the chain whip tool to fully seat the freewheel clockwise against the hub
Sprocket Inspection And Cleaning
In general, cassettes and freewheels are usually very dependable and require basic maintenance. It only requires that you wipe away any surface dirt and drop a little oil into the bearings periodically.
Want to do a thorough cleaning? Follow these steps to clean the sprockets:
- Remove the wheel from the bike and lay it down on a flat surface
- Use a stiff brush, like a toothbrush, to loosen the grimes on the teeth and use a rag to wipe them away
- Moisten the rag with solvent and wipe the grime off the surface of the cogs
- After cleaning the outer surface, hold the rag with both hands
- Pull it taut and slide it between each successive cogs, cleaning both sides of each cog with a shoeshine motion.
You can maximize the life of your modern cassette by replacing your chain periodically, recommended every 750 to 1,000 miles on the road, and more often when mountain biking or riding through rough terrains and bad weather.
Read more about How to Clean A Bike Chain (Step-by-Step Instructions)
Read more about How to Size A Bike Chain.
In conclusion, the process of removing and installing a rear cassette from a bike is relatively simple. With a few simple tools, a cyclist doesn’t need to be intimidated by the prospect of removing and replacing their cassette.