Bicycle Cassette – Impact and Compatibility

Bicycle Cassette – Impact and Compatibility

The bicycle cassette greatly determines the power and speed of the bicycle. So many people replace, upgrade and change the cassette size to get a more suitable bicycle performance. How does the number of cassettes affect and can all cassettes be replaced?

Freewheel vs Cassette

Before discussing the cassette, let’s see what terms are used and the types of bicycle propulsion systems.

Sprockets are gears or jagged metal circles that are rotated with a chain to turn the bicycle wheel. Cogset or cluster is a collection of sprockets mounted on the rear wheel hub. Cogset works with the rear derailleur to produce a variety of gear ratios on the bike. Cogset consists of two types, namely freewheel and cassette.

Although the function and form are the same, freewheel and cassette are two different things. Freewheel already existed before the cassette. Almost all modern multi-gear bicycles that exist today use cassettes. For simplicity’s sake, the difference between a freewheel and a cassette is that the cassette has an improved design and effectiveness over the freewheel.


Freewheel or also called block is a collection of sprockets mounted on a threaded hub. So like a nut on a bolt, the sprocket must be turned on the threaded hub to lock it in place. Almost all bicycles made until the late 1980s were freewheels. The freewheel system is simple but effective, if you want to change the sprocket size for the gear ratio, just open the one you want to replace and install a new one.

Freewheel bicycles have bearings on the inside of the freewheel body on the inside. The more sprockets that can be inserted create an unbalanced load on the axle, so it can bend or even break. So the freewheel can’t accommodate many sprockets, the most common being 5, 6 & 7, but some can go up to 9 speed, even a 10-speed freewheel like the Sunrace freewheel (but rarely). 

But not everyone wants to install too many sprockets on the freewheel, because the structure is not very supportive for many sprockets, and it seems the technology has not developed too much since the presence of the cassette and freehub.


Shimano developed a hub system which they called Freehub. The development of freehub is in demand and is also used by other manufacturers because the mechanism and structure are good and strong. So the popularity of freehub began to replace freewheel, and freehub became the new standard in drivetrain systems. 

The freehub has a ratchet mechanism and the bearings are attached to the bicycle hub and no more threads. Sprockets are installed by inserting them into the hub body which has a special spline shape to rotate the hub, and a lockring is attached at the end to lock the sprocket in place.

The advantage of the cassette over the freewheel is that the bearing position is wider and at the end of the sprocket assembly. It balances the pressure on the axle so that the axle is better protected from excessive pressure on one side, which is better for axle alignment and wheel rotation.

This collection of sprockets on the freehub is known as a cassette. To facilitate sprocket installation and regular sizing of sprockets and spacers, several sprocket units are usually joined and locked with a rivet into one piece, called a spider/cage cassette. Spider cassettes can also help reduce bike weight, as aluminum rivets or locking bolts can partially replace the heavier steel or titanium sprocket compositions.


The cassette is mounted on the bicycle, by inserting it into the slot in the bicycle wheel hub. Freehub is a type of bicycle hub that can accept cassettes. Cassettes cannot be inserted into freewheel bicycle hubs, and vice versa.

The freehub has a spline slot, and the cassette is inserted by pushing it in to follow the shape of the existing fin, then it will be locked at the end of the hub with a lockring. This spline functions as a binder for the cassette on the hub, so that if the cassette rotates, the hub and wheels will also rotate. The pattern and shape of the spline also vary, to ensure that the cassette that can fit is only a compatible cassette.

There are many forms of bicycle hubs, ranging from different times/technology, brands, and speed capacities. Read: what is inside a bicycle hub, to find out more about the types and contents of a bicycle hub.

Gear Range

Cassette consists of sprockets with different numbers of teeth (T). Usually, the naming of the cassette uses the smallest and largest sizes, for example, 11-32T 11 speed, which means that on the cassette there are 11 sprockets with the smallest sprocket measuring 11T, the largest being 32T. Each cassette must also indicate the size of all the sprockets in it, such as 11-32t: 11,12,14,15,17,19,22,25,28,32; so we can see the gradation of the existing sprocket sizes.


Cassettes are also classified based on the difference in the size of the smallest sprocket with the largest, into:


  • Narrow ratio cassette

If the difference between the smallest and largest sprocket is less than 20T. Cassette type narrow (narrow) is more widely used on racing bicycles, the difference in pedal strength when shifting is smoother, and does not require sprockets of extreme size.


  • Wide-ratio cassette

If the difference between the smallest and largest sprocket is more than 20T. This means that the cassette has very small or very large gears in the cassette. Wide cassettes are used on mountain bikes that require light pedaling uphill or on rough terrain, but can also be carried quickly.


Gear range is the ratio of the largest sprocket size to the smallest sprocket size in percent. For example cassette 11-32t, Gear range = 32/11 x 100% = 291%.


As we know, the smaller the sprocket, the easier it is to carry the bike fast, and the bigger the sprocket, the lighter the bicycle pedal when carried uphill. From the gear range we can see the character of the bike, the smaller the gear range means the bike doesn’t have much difference in pedal strength on the cassette, it is more directed to a bicycle that is specific to an area. The greater the gear range, the bike can be carried fast but also easy to climb, so the bike can be used in all conditions.


Gear range is not related to top speed and bicycle speed, bicycle speed is more determined by the combination of sprocket and chainring sizes and also bicycle wheel size. While the gear range does not take into account the size of the chainring.

Racing bikes usually have a smaller gear range than mountain bikes, because racing bikes are area-specific, chase speed, and don’t use sprockets that are too large. As for mountain bikes, the character wants to be light on the incline but also fast. So there are mountain bikes that have a gear range of 500% on a 12-speed mountain bike (10-50T), a 10T sprocket to make it fast, and a 50t sprocket to make it easy to climb.

The size of these sprockets has been arranged in such a way so that there are no spikes that are too large between one sprocket and another. So when shifting, the difference in pedaling strength is not too much different. This of course can be different for each person. Powerful people may not need contiguous sprockets that are only 1T or 2T apart.


The difference in the size of the adjacent sprockets that are too large is also not good in some cycling conditions or areas. There will be no problem on the way down. But on an incline, in particular, a gear difference that is too far in size will make us lose momentum or speed. Because the leg muscles are surprised when suddenly they have to move much harder to maintain speed. Usually what happens is that the speed of the bicycle decreases or even stops, so we lose the momentum of thrust, and have to start riding at low speed again.


The smallest and largest sprockets/gears are indeed the ones that determine the speed limit and power of the bike. But of course, looking at the combination with the chainring / front gear, for that there is something called the gear ratio.

Gear ratio

Gear ratio is the ratio between the size of the chainring and the sprocket used.

For example the Thrill Enthral Elite Racing Bike with chainring/crankset 50/34T and cassette 11-32T.

Minimum gear ratio =34/32=1.06 and maximum gear ratio 50/11=4.55

This means that when we use chainring 50 with sprocket 11, one rotation of the chainring will rotate the sprocket and wheel 4.55 times, we use this combination for speeding. To climb, we need a small gear ratio or a small chainring combined with a large sprocket.

For multi-speed bicycles (double let alone triple), there will be several gearing combinations that have the same gear ratio. Not wrong actually, but many feel that there are too many unused gears and complex shifting. So that a bicycle with a single chainring is considered more efficient and effective.

The smaller the gear ratio, the lighter the bicycle pedal (used when going uphill), and the larger the gear ratio the heavier the pedaling (used when descending & speeding).

Gear ratio also cannot be used to determine the maximum speed of a bicycle, nor can we compare the gear ratio values of several bicycles to determine which is the fastest. Because of the problem of speed limits (top speed), later it will depend on the size of the wheel and the speed of the pedal (cadence).

If you want to easily calculate or estimate gear range, gear ratio, and bicycle speed simulation, use a bicycle calculator.

So, to make the bike faster or lighter on an incline, changing the cassette or sprocket is not the only solution that can be done on a bicycle drivetrain, because many other factors play a role. Such as changing the size of the wheel, changing the size of the chainring, or accelerating the pedaling (muscle strength).

Cassette compatibility and upgrades

Often we feel the bike is too slow, or too heavy on an incline, while the gear is stuck, so sometimes we feel we need a bigger/smaller or more gear. Yes, this often happens, because of the mistake of buying a bicycle, or indeed the leg muscles are getting stronger because they are used to it.

Before upgrading or replacing a cassette, we must first know the type and specifications so that we can get compatible components.

Cassette width and sprocket spacing

The sprockets on cassettes 6,7,8 and so on may look the same, but they are not, because the difference is only a few mm. Shimano and SRAM sprockets are mutually compatible, meaning they can be interchanged, while the Campagnolo has different dimensions from sprockets in general.

On the cassette, the more sprockets (the more gears), the space or distance between the sprockets is also getting tighter, and the thickness of each sprocket is also getting thinner. Some freehubs can accommodate multiple gear sets.

Cassette racing bike VS mountain bike

Except for Campagnolo, SRAM and Shimano have the same dimensions for 7, 8, 9, and 10-speed cassettes, for both mountain bikes and race bikes. See the table above, the sprocket spacing, thickness, and total width are the same.

The terms MTB (mountain bike) and Road (racing bike) on cassette are just marketing terms. There is no difference in shape and spacing. What distinguishes it is the arrangement and size of the sprockets used.

A typical example of setting the 11-speed sprocket size on:

  • Mountain Bike (Road) 11-28T : 11-12-13-14-15-17-19-21-23-25-28
  • Gravel bike 11-40T : 11-13-15-17-19-21-24-27-31-35-40
  • Race Bike (MTB) 11-42T : 11-13-15-17-19-21-24-28-32-37-42

Of course, mountain bikes need a larger sprocket size to make it easier to climb on tough off-road terrain. So that the size jump (gap) between the sprockets is larger to accommodate the large sprockets.

While on a racing bike, there is no need for a large sprocket size, so the size between the sprockets can be adjusted more uniformly for smooth shifting and acceleration.

Gravel bikes, as bicycles that are similar to a combination of MTB and road bikes, use a wider cassette, similar to mountain bikes. Because if you ride on dirt roads/gravel, a bigger gear will make accelerating the bike easier.

The table below describes in detail the spacing between sprockets, sprocket thickness, spacers, and cassette width (thickness) for mountain bikes and racing bikes.

Can MTB cassettes be used on race bikes?

For Shimano and SRAM 8.9, and 10-speed cassettes, MTB and road bike cassettes are the same size (at the same speed), so they can be paired or exchanged. But other components (chain, RD, shifter) must support if there is a change in size or number of sprockets.

12-speed cassette

Cassette and groupset 12 speed has their standards. In the early days of the 12-speed groupset, Shimano and SRAM had a special freehub for the 12-speed cassette. SRAM must use the HUB XD driver, and Shimano can only be used with micro spline hubs. But SRAM finally released the NX Eagle groupset which has 12 mountable cassettes and is compatible with standard freehubs (8-11 speeds). And after that, many cassette products produced by other brands can also enter the standard freehub.

As sprockets get thinner, especially on large/slow gears, manufacturers usually attach them into one piece, called a cassette spider or cassette cage. If we open the cassette, usually the 3 or 4 largest sprockets are already a set/bundle attached. Because large and thin sprockets are more prone to bending or breaking, they must be strengthened by joining several sprockets together.

Making the sprockets into a set can also save significant cassette weight. The sprocket ring does not necessarily have to consist of solid metal to the hub. Only the largest and smallest sprockets are connected to the center (hub). For example, the Garbaruk 10-50T 12-speed cassette, weighs only 342 grams. The disadvantage of this spider cassette or cage cassette is that if one sprocket is damaged or chipped, it will be more difficult to replace just one sprocket size.

The more speed/sprocket usually makes the cassette heavier. But that’s not always the case. The technology and method of preparation and materials for cassettes are also adapted to produce lightweight cassettes even though the speed is increased. For cassettes, the weight usually ranges between 300-600 grams, the more expensive the cassette the lighter the weight, because it uses strong and light alloy materials and more complex assembly techniques.

The Shimano HG500 10-speed example (11-42T) weighs 435grams, compared to the Garbaruk 12-Speed Cassette (10-50T) which weighs 342grams. The Shimano HG500 uses unit pieces that are combined into one, while the Garbaruk 12-speed assembles all sprockets into one spider/cage, so not all sprockets must consist of solid pieces.


Cassette spacers are additional metal plates that are installed so that the spacing between the sprockets is uniform or so that the cassette width can fit into the freehub.

The thickness of the sprocket and spider/cage cassette will affect the installation position of the spacer. Each cassette can have a different spacer position. So when opening or disassembling a cassette, it’s best to keep or remember the order or position of the sprockets and spacers. Leading cassettes, usually in their guide or website, provide information, about their cassette arrangement.

Cassettes are not always sold in a set, some are sold per sprocket. Usually used to replace one of the damaged sprockets, or want to change the size of one or more sprockets.

For a loose sprocket, replacing it with similar size is of course easy. But replacing sprockets of different thicknesses or adding new sprockets is not that easy. We have to pay attention to the thickness too. Because for each speed, the thickness is different. If it is too thick, it will certainly shift the position of the sprocket on the left, and the shifting will not be smooth. Due to the distance the chain shifts by the derailleur, it is no longer the same as the distance between the sprockets.

But if it is thinner than the original sprocket, spacers can be added to get the original cog pitch. But measuring or finding the thickness of the spacer with a precision of mm is a bit difficult unless it is given when buying a new sprocket.

But if it is thinner than the original sprocket, spacers can be added to get the original cog pitch. But measuring or finding the thickness of the spacer with a precision of mm is a bit difficult unless it is given when buying a new sprocket.

Cassette and freehub compatibility

How about installing a cassette on a different brand of hub, or upgrading a 10-speed cassette on an 8-speed hub? There are so many possible combinations of cassettes and hubs that can be made, due to the difference in the number of sizes and brands.

For cassettes and hubs, most refer to the standards from large manufacturers such as Shimano, SRAM, or Campagnolo, but not infrequently use their dimensions which are usually described in the specifications. To be sure, not all cassettes and hubs are compatible, even though they are both 10-speed, for example. In some cases, spacers can help to make the cassette fit in width on a freehub body.

From this table, we can see that if an 8,9,10 speed cassette fits on the same bicycle freehub (except Campagnolo), a 7-speed cassette can also fit with an additional spacer. Or an 11-speed cassette can only be attached to an 11-speed hub.

Although 8,9,10 speed cassettes have different widths, when inserted in a compatible hub, lockrings and spline grooves that are still good will usually lock the cassette well. Sometimes a problem occurs when the lockring thread is jammed or damaged, so it cannot be locked properly/until it runs out, thus requiring additional spacers.

For Shimano 12 speed while it can only be used on micro spline freehub. SRAM also initially only made 12-speed cassettes for the XD driver body, but SRAM has released the SRAM NX Eagle cassette which is compatible with the 8,9,10 freehub. But the smallest size of SRAM NX Eagle sprocket is 11T, and can’t fit 10T. The 10T sprocket, can only be paired with the XD driver.

Although cassette and hub are compatible, that’s not enough for the drivetrain to work, we must always look at compatibility with other bicycle drive components.

What effect does the number of cassette sprockets have?

Changing the number of sprockets on a bike in terms of performance will inevitably change the gear range and gear ratio. The above also explained compatible cassettes and hubs, but in a bicycle drivetrain system, cassettes and hubs must also be compatible with other components. What matters when we replace the cassette with a different speed or number/size of sprockets?


As discussed in How a derailleur works on a bicycle, shifters and derailleurs for different speeds have different specifications. For each number of speeds, when the shifter lever is depressed, the derailleur must shift equal to the width between the sprockets (cog pitch). This allows the derailleur to slide the chain so that it attaches to the sprocket next to it.

So it can’t be forced, a shifter for a certain speed is applied to a cassette with a different number of sprockets.


For cassettes with different sprockets, a different type of chain is required as well. If the sprocket is getting thinner, the chain must be getting thinner as well. It will be difficult if we use a chain for 8 speeds on an 11-speed cassette. Because the shape of the 8-speed chain is thicker, making it difficult to fit in the gap and the thin 11-speed sprocket body. Therefore, bicycle chains of 10 speed and above usually wear faster than low-speed bicycle chains. So, when we change the chain or change the cassette, we need to pay attention to the compatibility between the two.

The chain length should also be changed when the number or size of sprockets is changed.

Rear Derailleur

Another thing to consider when changing the number and size of the cassette is the Rear Derailleur (RD). The derailleur has the capacity for sprocket and chainring sizes that can be attached. The limit is the actual chain length, the derailleur has the function to roll up the remaining chain from the sprocket and chainring combination.

The larger the sprocket and chainring the longer the chain is required, and when used in a certain gear position, the derailleur will roll up the rest of the chain to maintain chain tension. The longer the derailleur, the more chains it can roll, this is what makes the derailleur capacity will limit the sprockets that can be attached to it. So not all sprockets can fit into a particular derailleur.

Cassette Profile

The sprockets on modern cassettes have a unique profile and shape. Not only do the teeth protrude like old sprockets, but have a shape whose purpose is to make it easier to shift the bicycle chain. The part of the sprocket that looks “coak” is called the ramp. This ramp is like a path to move and catch the bicycle chain better, especially for sprockets that are much larger than the sprockets next to them. That way, shifting will be faster and smoother. Not only that, but the ramp will also reduce the weight of the cassette.

Especially for mountain bikes that use a wide range of cassettes, surely in the large sprocket, the difference in the size of adjacent sprockets will be more extreme. This makes the chain somewhat more difficult to move from one sprocket to the next, as it has to climb higher.

Tooth profiles are also often modified in shape for the same purpose. Some are long and short, or some are reversed alternately. The same applies to the chainring. The chainring also sometimes added a kind of pin, to catch and release the chain. Because the chainring is usually a much more extreme size difference and the distance between the gears is more tenuous.

Cassette Precision Level

If we look at the table above, the more speed, the thinner the distance between the sprockets. This also makes, the level of precision shifting, must be more precise with the increase in the number of speed/sprockets on the cassette.

On an 8-speed cassette, the distance between the sprockets is 5mm, a 0.1mm difference is still within tolerance. But at 9,10, 11, and 12 speeds, where the distance between the sprockets is getting closer, the 0.1mm difference can be a problem, resulting in difficulty/jamming during shifting, chain skipping, or over the sprocket next to it, and so on.

After upgrading or replacing a cassette or sprocket, if the shifting and gearing are not smooth, it may be one of the problems with the level of precision of the size that is still not right. Differences of a few millimeters are indistinguishable to the eye, so pay attention to specifications and correct measuring tools.

Even on a 12-speed bicycle, the use of electronic shifting is considered safer, because it requires very good precision, the electric motor will provide regular and uniform shifting, compared to hand pressure and manual mechanisms. Like the Shimano Di2, SRAM eTAP, or Campagnolo EPS.

This makes cassettes with higher speeds more expensive because of one of the factors of more careful manufacture and higher precision. Likewise, other supporting components must also have a high level of precision as well. So we need a little extra care for modern bicycles that have a lot of speed. Unlike older bikes that are more durable, components that miss a bit can still be run.

Copyright © 2023 GRVL Bicycle