The cassette is the set of gear sprockets (or ‘cogs’) that sits on the right hand side of your rear wheel and meshes with your chain to propel your bike forward. As with a replacement bike chain, it’s important to make sure your new cassette is compatible with the rest of your drivetrain – plus it needs to fit on your wheel.
Here’s how to find the right cassette to replace yours. But first up, why would you want to replace your cassette?
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When should I replace my cassette?
Pedalling, changing gears and the road grunge you pick up while riding will progressively wear your bicycle chain and cassette. Chains stretch and as a result, the tooth profiles of the sprockets in your cassette change, so that they gradually become sharper and the flat parts between them larger.
That results in progressive degradation of shifting performance, so your gears might skip. You’ll also see changes in the tooth profiles in your chainrings, but because there are a lot more teeth in the chainrings in contact with the chain, the result may not be as pronounced. On the other hand, chainrings are often more expensive to replace than the cassette, so you’ll want to try to reduce chainring wear.
We’ve got a guide to how to check your chain for wear; in general, when it shows 0.75 per cent wear it’s considered time to replace your chain. You should replace your cassette at the same time too, or shift quality may become even poorer.
Of course, derailleurs will work with multiple sizes of cassette, so you may also want to replace your cassette to get a wider or narrower spread of gears or you may have just bought some shiny new wheels and need a cassette to fit to them.
How to choose the right cassette for your bike
There are a few things you need to get right for your cassette to work with your gearing and your wheels.
First up, a new cassette has to have the same number of sprockets ('speeds') as the one you’re replacing, otherwise it won’t work with your shifters and rear derailleur and it might not fit on your rear wheel. If you’re not sure, count them.
Your cassette also needs to be compatible with your rear derailleur, which will have a limit for the number of teeth it can work with in the largest sprocket.
You can’t use a cassette with a largest sprocket that has a greater number of teeth than this, so for example you cannot use an 11-42 tooth gravel bike cassette unless you have a derailleur specifically designed for it.
Some derailleurs, including those from Shimano, also have a limit for the smallest-size large sprocket that they’ll work with. You can check the permissible range on the derailleur maker’s website. Sometimes brand specs are conservative and you can get away with pushing the limits by a couple of teeth or so, but you do so at your own risk – don't expect any warranty cover if a component fails as a result of doing this.
How do I make sure my cassette will fit my wheel?
Next it gets even more complex. Your replacement cassette needs to fit on your wheel’s freehub. There are multiple freehub standards and they're not interchangeable with one another.
- Read our full guide to freehub standards
Shimano-style freehubs
The most common type is Shimano/SRAM 11-speed, which has flanges that mesh with the cassette. A lock ring, which usually comes with the cassette, is used to hold the cassette sprockets in place.
If you have a bike with ten speeds or fewer, you’ll need to use a 1.85mm spacer for a ten-speed cassette to fit securely on an 11-speed hub. You should find that there was a spacer in place when you remove your old cassette, which can be reused.
Older bikes may have a slightly narrower 10-speed freehub on the rear wheel. Shimano 105, Ultegra and Dura-Ace 10-speed cassettes will need a 1mm spacer to fit. If you’re mounting them on an 11-speed freehub, you’ll need to supplement this with a 1.85mm spacer as well.
Mountain bike cassettes are slightly narrower than road bike cassettes with the same number of speeds and so are not generally compatible with road bike wheels unless you use a spacer.
Shimano 12-speed groupsets use a newer standard called HG Spline L2 with more splines in the freehub and cassette, but fortunately it’s backwards-compatible with 11-speed hubs.
Shimano Micro Spline mountain bike hubs and cassettes with a similar-looking spline pattern are not compatible with road bike components. To complicate things though, Shimano's latest single chainring 12-speed GRX RX820/RX610 groupset uses an MTB Micro Spline freehub to accommodate its cassettes, which all start with a 10-tooth sprocket. The double chainring version uses cassettes starting at 11 teeth and a standard HG11 11-speed freehub.
Shimano launched CUES for drop bar bikes in January 2025. When it comes time to replace your CUES cassette, it uses a different tech called Linkglide, rather than the Hyperglide used for the above groupsets, so you'll need a Shimano CUES cassette to work properly.
Campagnolo freehubs
Another freehub standard is Campagnolo 11/12-speed. Campagnolo freehubs have deeper grooves in their flanges and a Shimano cassette won’t fit; you need a Campagnolo-specific cassette. There’s a specific locknut needed to secure the cassette to the wheel too.
Campagnolo’s latest wheelsets use a new standard that it calls N3W. This mates a shorter freehub with the 13-speed cassettes used by the Campagnolo Ekar gravel bike groupset, but is also backwards-compatible with 11/12-speed Campagnolo cassettes when used with a special adapter.
SRAM XD/XDR freehubs
Yet another standard used on road bikes is SRAM XDR. This is used for SRAM 11 or 12-speed cassettes and allows a ten-tooth smallest sprocket to be used.
The XDR cassette initially pushes then screws onto the XDR freehub body and doesn’t have a lock nut. SRAM also makes XD cassettes for mountain bikes, but these are narrower than XDR cassettes and won’t fit on an XDR freehub without a spacer. You can’t fit an XDR cassette on a wheelset with an XD mountain bike freehub.
Again there's an exception. The Apex Eagle 12-speed groupset uses a range of cassettes with MTB spacing, which will fit on an XD freehub or an XRD freehub with a spacer.
There are also cassette options for Apex XPLR and Apex Eagle which have an 11-tooth smallest sprocket and fit on a standard HG11 Shimano/SRAM freehub.
What if I don’t have a cassette?
Not all bikes have a cassette. A single speed bike will have a single sprocket with a freewheel mechanism included that threads onto the hub. If it's a fixed gear single speed bike, there's no freewheel and the sprocket will be held in place by a reverse-threaded lock ring. Many single speed bikes will have a flip-flop rear hub that lets you set them up with a freewheel on one side and a fixed sprocket on the other.
In the past, bikes used a freewheel, aka a block, which included the freewheel mechanism in the freewheel body and threaded onto the hub. You need a differently designed set of gears to work with this system and different tools to change the freewheel.
Should I just buy like-for-like?
As with bicycle chains, if you're just replace your existing model with the same one you’re not going to have any problems. If you want a wider or narrower gear range, though, you’ll need to check derailleur compatibility, as above.
Again, like chains, you can save a significant amount of cash by downspeccing through the manufacturer’s groupset range. A 12-speed Shimano Ultegra 11-34 tooth cassette, for example, will work exactly like a 12-speed Shimano Dura-Ace 11-34 tooth cassette, it will just be a little heavier and a lot less expensive.
Make sure that a replacement cassette has the same number of sprockets as the one it’s replacing, though. Groupsets typically add a speed from one generation to the next, so you can, for example, find a Shimano 105, Ultegra or Dura-Ace cassette fairly readily with 10, 11 or 12 speeds.
For systems with 11-speeds and fewer, SRAM and Shimano road bike cassettes are interchangeable with each other. Their 12-speed road bike cassettes are not, though.
You can also buy cassettes made by other brands such as Miche. Provided they have the right number of speeds, correct gear range and use the same freehub standard as your current cassette, these should be compatible with your drivetrain. They are sometimes cheaper than brand-matched components.
What do I get if I spend more money on a cassette?
A more expensive cassette will, in general, be lighter than a cheaper one. That may be because it’s been made of more exotic materials or because it’s been machined more.
Shimano’s top spec Dura-Ace cassettes, for example, have their largest sprockets made of titanium, whereas in Ultegra and 105 these are steel and mounted on an aluminium alloy spider.
In the case of SRAM, its range-topping Red cassette is machined from a single steel billet, while 12-speed Force cassettes have a single piece for the smallest four sprockets and the larger ones are individually pinned to the cassette body. Durability may be greater and a cassette made from fewer components could be more rigid, but that’s not necessarily the case.
You might get flashy finishes too, as in the latest iridescent SRAM Red cassette or the Recon Racing cassette that is also iridescent and weighs just 94g.
What tools do I need to change a cassette?
Removing a cassette and adding a new one requires a few tools that are specific to the job.
First, you’ll need a cassette lock nut tool. This slots into the flanges on the locknut that holds your cassette in place. Most then require you to use a large spanner to loosen the lock nut, but you can get all-in-one lock nut tools with a handle. Lock nuts are different between Shimano/SRAM and Campagnolo cassettes and you need the appropriate tool for each.
If you try to loosen the lock nut, you’ll just turn the whole cassette with its freewheel mechanism, so you need a chain whip to hold the cassette in place. This usually takes the form of a metal bar with a short length of chain attached. You wrap the chain around a sprocket on the cassette, which lets you brace the cassette while loosening the lock nut.
Once you’ve removed the lock nut, the cassette sprockets should just slide off the wheel’s freehub. Be careful to catch any spacers on the inside end of the cassette as you’ll need them when you add your new cassette. Now is a good time to clean the freehub and the area around the hub flange, which is usually very hard to get at with the cassette in place.
Next you need to slot the new cassette onto the freehub body. The flanges on both are designed so that the sprockets will only fit on the freehub in one position and one orientation, so you need to get both right. That’s so that the ramps and tooth positions in the sprockets are precisely aligned to ensure smooth shifting. It can be fiddly and may be messy if your freehub is a little dirty. Your new cassette may be greasy too. Gloves are handy.
Once all the sprockets are threaded onto the freehub, you can add the lock nut. Do this very carefully by hand, as it’s easy to cross-thread, potentially destroying an expensive freehub. If the lock nut doesn’t seem to be going on correctly, remove it and try again – never use a tool to force it on.
Once you’ve got the lock nut on correctly and it’s flush with the sprockets, you can use your lock nut tool to tighten it. It needs to be tightened firmly to ensure that it stays in place under load – 40Nm is the usual quoted torque value. If you’ve got everything set up correctly, your cassette sprockets should be held firmly together on the freehub with no play. If they do move, you may have forgotten a spacer.
If you have a freewheel rather than a freehub and cassette system, you’ll need a different tool to mesh with the freewheel and unthread it from the wheel and then tighten your replacement in place. You don’t need a chain whip, though.
Best cassette: Our picks for every major current groupset
You can usually choose from a range of different cassettes that will work with your gears. While there's no single best option, here are our picks to balance value and performance. We've also mentioned some flashy options if you want to save a little weight, but bear in mind that a cassette and chain probably won't last more than a year of steady use, particularly if you ride through winter.
Best cassettes for Shimano groupsets
Shimano Dura-Ace/Ultegra/105 12-speed and Shimano GRX 2× 12-speed
For the best of the best, a Dura-Ace cassette will match your drivetrain and give you titanium larger sprockets – but at a price. For around half the cost, a Shimano Ultegra 12-speed cassette will give you the same gear ratios and preserve the Hyperglide+ shifting, which 105 12-speed does not have. Fit Ultegra and there's a weight penalty of around 100g relative to Dura-Ace.
If you're running Shimano GRX 12-speed single ring, you'll need an MTB-style cassette. We'd recommend the SLX-level M9100 cassette.
Shimano Ultegra/105/GRX 11-speed
For Shimano's 11-speed groupsets, again there's a choice of Shimano cassettes available and a downshift to 105 will save you some cash over an Ultegra cassette with the same ratios. It will work with the GRX 2× 11-speed gravel groupset as well. If you want ultimate lightness though, the Miche Supertype cassette drops the weight of the component down to under 150g.
Shimano Tiagra/GRX 10-speed
At ten speeds, the Shimano HG500 cassette is a good option which works with both the Tiagra road and GRX400 gravel groupsets. It offers four range options from 11-25 all the way up to 11-34, so there's plenty of choice to suit your riding style.
Shimano Sora 9-speed
Another Shimano option which gives you a wide range of ratio choices, the HG400 MTB cassette is available in six different configurations from 11-25 all the way up to 11-36. You'll need to use a 1.85mm spacer, but cassettes up to 34t are otherwise compatible with Sora groupsets and give you some wide range choices.
Shimano Claris 8-speed
Among aftermarket brands, Microshift gives you good compatibility with Shimano groupsets and consistently undercuts the price of the Japanese components. It's durable and gives you a range of five different ratio spreads.
Best cassettes for SRAM groupsets
SRAM Red/Force/Rival/Apex AXS 12-speed
For SRAM's 12-speed groupsets, you'll need an XDR cassette (or an XD MTB cassette with a spacer). SRAM Red cassettes are beautifully made from one piece of steel and you can now buy one in rainbow colours. The more considered choice is probably the Rival cassette though – as with Shimano's offerings, you can save a significant amount of money and it's likely to be as durable, just heavier than the Red option.
There's a complication if you're running SRAM Apex Eagle, as you'll need an MTB-style cassette. We'd recommend the NX Eagle cassette.
SRAM Force/Rival 11-speed
As with Shimano 11-speed drivetrains, there are multiple levels of 11-speed SRAM cassettes available that will work with SRAM 11-speed groupsets. The PG-1130 cassette is the cheapest of these and offers a good range of gear options. Be careful to ensure that your derailleur is compatible before ordering options with 36 or 42 teeth, which need a Force 1/Rival 1 derailleur. Ranges up to 11-32 should work with a standard 11-speed drivetrain, and you'll need to use a 1.85mm spacer to fit it on road bike wheels.
SRAM Apex 10-speed
The SRAM PG-1030 cassette covers a similar range to the PG-1130 above, just in ten sprockets instead of 11. It too is an MTB cassette and so will need a 1.85mm spacer on road bike wheels, and you need to ensure that your derailleur is compatible with wider range cassettes.
Best cassettes for Campagnolo groupsets
Campagnolo Ekar 13-speed
You are going to need an Ekar cassette to work with Campagnolo's gravel groupset. It's available in three gear ranges though, so you can fine-tune your cassette choice to match your riding terrain. Ekar GT adds a 10-48t option, although this can't be used with the original Ekar. Speccing an Ekar GT cassette will save you a little money relative to an Ekar cassette and weights are comparable.
Campagnolo Super Record/Record/Chorus 12-speed
As with Shimano's 12-speed groupsets, if you go for the top spec Super Record cassette you'll save a little weight but the price doubles over the Chorus 12-speed cassette. We'd recommend speccing the latter.
Campagnolo Centaur 11-speed
An in-series Campagnolo Centaur cassette is fairly inexpensive and will give you three different gear range options.
Best single speed sprockets
A single speed sprocket is an inexpensive item. Miche has a good reputation for its track components, and its sprockets are available in a range of size options and 1/8in and 3/32in, so you can fine-tune your ride. If you want to replace your single speed freewheel, Token Shark Bite freewheels are well-made and should be durable.
Need a chain to go with that? Read our guide to the best bike chains and how to choose a replacement chain
