If you want a different range of gears such as lower gears for a holiday in the mountains or tighter gears for racing, the easiest way to achieve that is to change the sprockets on your rear wheel. Here's how to do it.
Sprockets mount on a splined cylinder on the rear hub, called the freehub body. The collection of sprockets is held in place with a lockring.
Modern shifting mechanisms like Shimano's Hyperglide and SRAM's PowerGlide chain-and-sprocket combination rely on correct alignment of shaped teeth and contoured shift gates in the sprocket. To keep this alignment right, the splines on the freehub body are uneven, with one spline larger than the others, so there's only one way the sprockets can fit.
Removing a cassette is the only worthwhile way to clean it. Do so as often as you feel like getting grubby, if you ride in the winter and dirt regularly then it could and maybe should be a weekly thing.
Our guide below shows you what we believe is the best method to fit and remove cassette sprockets. We've included a list of the tools and materials that you will need to complete the job and in some cases where you can buy them. If there are others that you prefer then feel free to let everybody know in the comments.
Most lightweight cassettes use one or more stepped alloy carriers for the sprockets which are usually heavily drilled and machined to remove every last gram of surplus material. On some high end cassettes aluminium or titanium is used in place of steel, especially on wide ratio models where the weight saving is greatest and individual tooth loads lower. The cassette pictured below is a SRAM model with the 36-tooth largest sprocket made of alloy while the other nine are steel.
1 Position the chain whip
Wrap the long loose end of the chain whip over the top of the cassette as shown so that it is pulling the sprockets clockwise. Engage the fixed portion of the chain whip on the lower portion of the same sprocket that the loose end is attached to. It's best to use one of the middle to upper sprockets, just ensure you've got a good wrap on the sprocket. When it feels firm enough to place a decent amount of pressure on, you're ready to get the cassette removal tool fitted.
2 Insert the lockring tool
The cassette lockring tool is sometimes integrated with a handle like this one, or it may be a separate tool that needs an adjustable spanner to give leverage. The spines on the tool will match those inside the lockring. The tool handle (or spanner handle) should be positioned to be a reflection of the chain whip. So if you look at the two tools in their fitted state they should resemble clock hands at 'ten to two'. Make sure the tool and lockring are fully engaged before you apply removal pressure. The lockrings are often light alloy and it's very easy to tear the teeth.
3 Unscrew the lockring
With the chain whip is in position and lockring tool in position, apply downward force on both handles. The chain whip will stop the cassette (and freehub) from turning as the lockring tool unscrews the lockring and breaks its grip on the smallest sprocket.
4 Remove the lockring
Once the lockring is loose, unscrew it from the freehub body. You'll see it come away from the cassette like this. Remove the chain whip and slide the tool and lockring out of the way.
5 Remove the sprockets
in the case of this particular cassette, the top three sprockets (11, 13, 14) are loose and they slide straight off. The remaining seven sprockets are all mounted to an alloy carrier body, so they can be removed as one unit. Here you can see them being slid off the cassette body (the white bit). Occasionally they can be a bit stiff to remove if the cassette splines have bitten into the freehub splines. Grasp the opposite edges of the largest sprocket and give a pull and a wiggle at the same time to get them moving.
6 Clean the freehub body
Freehub bodies get a raw deal in life, carrying all the load and getting precious little reward. When you get to see yours, give it a clean.
Now you've got the splines in clear view, you can see that they're not all even in size and spacing, as mentioned above, so that the teeth always align as the manufacturer intended.
8 Fit the new casette
Here you can see the splined black alloy carrier of the replacement cassette going on. It's holding the four largest sprockets. The narrow/wide splines are clearly visible at the twelve o'clock position.
9 Fit the top sprockets
Sprockets that are not permanently mounted to alloy carriers (and are therefore already correctly spaced) will have separate plastic or alloy spacers. These keep the sprockets the correct distance apart for accurate shifting. Sometimes these spacers are just plain rings (like the one pictured here), however sometimes they too have splines, though when they are splined they have a number of 'clocking' positions they can be fitted at any position.
10 Fit the last sprocket
The smallest sprocket, here a 12-tooth, should fit and its outer face be just proud of the outer lip of the freehub body, the white bit in this shot. This means that when the cassette is tightened down with the lockring all the sprockets fit together tightly.
11 Fit the lockring
Screw the lockring into position with your fingers. The threads are quite fine and if the lockring is made from aluminium, they'll therefore be quite fragile. Take care not to cross them. The lockring should require only light force to turn it until it touches the top sprocket.
12 Tighten the lockring
Make the final tightening of the cassette lockring with the lockring tool. The official torque setting is 40Nm. We tightening it until we feel the serrations on the lockrings inner face binding with the serrations on the outer face of the smallest sprocket.