Bike cassette replacement

If you’ve removed your cassette to transfer it to a new or different wheel, clean it or work on the wheel you will need to refit it. Following on from our last guide where we explained bike cassette removal we have put together a tutorial on bike cassette replacement.

Reasons for bike cassette replacement

  • Removing it to wash it- It is possible to clean your cassette while it is on the bike. We have a video and blog post on how to wash a bike if you need some guidance, however, some people like to remove the cassette to clean it.
bike cassette replacement
  • To service the hub- Generally it’s not possible to access the bearings in the rear wheel without removing and replacing the cassette.
  • To remove the freehub body- The cassette always has to be removed to access the freehub body.
  • To replace a spoke- The cassette blocks access to the spoke holes in the hub.
bike cassette replacement
  • To replace a rear wheel
  • To fit a new cassette- The old one is worn or you want a different ratio.
bike cassette replacement

Tools required for bike cassette replacement

  • Cassette removal tool- This slots into the lockring. Some of the tools are equipped with a lever so you don’t need a spanner.
  • Spanner-  This needs to be big enough to fit onto the cassette lockring tool.
bike cassette replacement

Compatibility when fitting a new cassette

  • If you are replacing the cassette with one that has more teeth on the low sprocket, then make sure that it is compatible. To do this, first check the maximum low sprocket capacity on your rear derailleur. Find a code or serial number. It is either on the back of the derailleur body or the back of the inner cage.

Use this code to find if the derailleur is compatible. We’ve added some useful links here

SHIMANO: https://bike.shimano.com/en-EU/home.html

SRAM: https://www.sram.com/en/service. Type the derailleur code in the search box

If the amount of teeth is greater, then shifting on to lower gears might be impossible.

bike cassette replacement
  • Now check the maximum drivetrain capacity. This is the amount of chain that the derailleur arm can handle.
  • To see if your chainset and cassette will work with the maximum drivetrain capacity of your derailleur follow the method below:
  • Count the number of teeth on the biggest and smallest chainrings.
  • Subtract the smaller number from the larger.
  • Count the number of teeth on the biggest and smallest sprockets of your cassette.
  • Subtract the smaller number from the larger.
  • Add these two numbers together. If this number is greater than the maximum drivetrain capacity then the rear derailleur won’t be able to function properly at the extremes.
If you’re not sure what is the maximum drivetrain capacity for your derailleur let us know in the comments below and we will advise you.

Compatibility when fitting a new wheel

If you are fitting the original cassette to a new wheel you will need to make sure that the number of sprockets on the cassette are compatible with the freehub body. For example, to fit a 10 speed cassette onto a new wheel it is important to check if the spacer is required as the freehub body might be designed to accommodate up to 11 cogs. The spacer should be included with the rear wheel. If it isn’t you will need to purchase it separately. 

A 7 speed cassette will fit on any freehub body, but may need spacers fitted behind the cassette to pad it out. 8, 9 and 10 cogs will fit on any freehub body that isn’t a 7 speed.  You may need a spacer behind the cassette. 11 cogs will go on an 11 speed freehub or a 12 speed but with a spacer and a 12 speed cassette will only go on a 12 speed freehub body.

Bike cassette replacement process

The cassette is built out of cogs and spacers. Most of the bicycle cassettes have these riveted together apart from the few highest gear cogs.

Some cassettes come with loose cogs and spacers.

In this section we explain how to replace the bike cassette:

  • The freehub body has splines of different thicknesses and this corresponds to the splines on the sprockets.
  • Find the widest spline on the biggest cog or cluster of cogs and match them with the widest gap on the freehub body. Slide the cog or cluster of cogs onto the freehub body. 
  • For the cassette with loose cogs now it’s time to fit the spacer. You will have a number of spacers and they should be all the same thickness. Pick one and slide on the freehub body.
  • Repeat the process with all the cogs and spacers starting with the biggest cog and finishing with the smallest. The last two cogs will be thicker with built in spacers. 
  • For the cassette with cluster cogs now fit the smallest sprockets. First fit the largest of these cogs with the spacer on the inside

and then the smaller one in the same way.

  • Put a small amount of grease onto the threads of the lockring.
  • Now hand tighten the lockring using the cassette tool.
  • When it is hand tight, use a wrench to secure the lockring.  This has to be tight. If you have a torque wrench then the required torque is 40 NM. As it tightens you will hear a cracking sound. This is normal and is the sound of the ridges on the lockring running over the ridges on the top sprocket and ensuring that the lockring won’t loosen in use.
  • Finally, give your cassette s spin to make sure that everything is lined up and running smoothly.

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