Bike Cassettes: What Every Cyclist Should Know

If you are looking to purchase a new bike, or to do a bit of maintenance on one you already own, you’ve probably come across a bunch of cyclist jargon. One of the more common terms you might have encountered is “cassette”. But what exactly is a bike cassette, and why does the term show up so often?

In this article, we will answer this very question, breaking down what a bike cassette is, how it works on your bike, and make sure you aren’t left confused the next time you’re in a bike shop.

What is a bike cassette?

In short, a bike cassette is a series of components. Specifically, this is the set of sprockets found at the back of the bike. This component, when attached to a rear derailleur, allows the rider to switch between gears during their ride. Switching gears will move the derailleur from one sprocket of the bike cassette to another, changing how the bike behaves. Some gears will increase your bike’s speed, while others will slow it down. Which is appropriate depends on the terrain.

Although the bike cassette is only a collection of sprockets at the back of the bike, it is a pretty in-depth component, one with significant influence over how a bike performs. As we mentioned, it affects the speed of a bike and how easy it is to ride, but this isn’t solely the remit of the sprockets themselves. The sprockets work as a cohesive unit, allowing for the seamless transition of the chain between one sprocket and another, and the derailleur works with both the sprockets and chain to ensure a smooth change between gears. As the sprockets within a cassette rely so much on one another, it is highly unlikely that replacing any one sprocket would be a good idea. For this reason, a cassette is most often replaced in its entirety, rather than bit by bit.

Also Read: How To Put a Bike Chain Back On

Why do bike cassettes come in different sizes?

As you’ve probably noticed while browsing in a bike shop, bike cassettes come in a range of sizes, denoted by two numbers. For example, a bike cassette may sport a size of “10-48”. But what does this mean?

It can be easy to interpret these numbers as the number of sprockets or their size, but neither is the case. Instead, these figures refer to the number of teeth on the sprockets. The first figure indicates the number of teeth on the smallest sprocket, while the second indicates the number of teeth on the largest sprocket. While it might seem odd to only focus on the two extremes, it is because the smallest and largest sprockets have two distinct roles, while everything else falls somewhere in between. The smallest sprocket, for example, is used when speed is the most important factor. You’ll use this sprocket when cycling downhill or on even terrain, with each pedal generating as much speed as possible. On the other hand, the largest sprocket is for getting a purchase on rough terrain or a steep gradient, such as hills or a rocky mountain trail. While every other sprocket certainly has its place, these two are arguably the most important.

Also Read: Freewheel vs Cassette: What’s The Difference?

Types of bike cassette

As you might have guessed, different sizes of sprocket, and by extension cassette, are best suited for some terrain over others. For example, a cassette designed for rough trails and terrains isn’t going to perform as well on a road downtown. For this reason, you should make sure the cassette on your new bike matches the terrains you intend to ride in.

Mountain bike cassettes

Generally speaking, mountain bike cassettes boast a wide array of gears that allow a cyclist to tackle any terrain while out on a ride. It’s quite common to find mountain bikes with a 12-speed cassette, meaning it has 12 sprockets to switch between. This is to make sure that mountain bikers have the means to handle almost any gradient, both inclines and declines, along with rough and smooth terrain, without losing too much speed or requiring unnecessary effort. However, although mountain bike cassettes offer good gear variety, they don’t offer the same variety in size. There aren’t a whole lot of different sizes, with some manufacturers only offering a very small number. Shimano, for example, offers two cassette sizes for their mountain bike range: 10-45 and 10-51. This limited choice in size can be restrictive if you want something geared toward a more specific scenario. For that, you might want to consider another type of bike cassette.

Gravel road bike cassettes

Gravel bike cassettes are essentially a middle ground between mountain bike cassettes and road bike cassettes, which we will cover next. In the past, gravel bike cassettes used to be rolled up into one of the other cassette types. Now, they have their own dedicated cassette type, for cyclists that regularly ride along gravel roads. SRAM, for example, manufactures a bike cassette specifically for gravel road riding, with their XPLR cassette having a range of 10-44. However, although there are gravel road-specific bike cassettes now, the selection is still sparse compared to other cassette types.

Road bike cassettes

Whereas mountain bike cassettes are designed for terrain adaptability over much else, road bike cassettes are more inclined towards speed. They tend to have a good number of gears, but sport a much smaller jump between sprocket sizes than mountain bike cassettes. For example, the average road bike cassette will be around 11-32, with many boasting a 12-speed cassette, similar to some mountain bike cassettes. This means that road cyclists can switch between gears to match most roads and conditions, eliminating the need to persevere through lower gears and wear out them, knees, and patience. Although this all makes road bike cassettes great for smooth road cycling, they aren’t as effective as mountain bike cassettes when it comes to rough terrain and inclines.

Wrapping up

All in all, each bike cassette is best suited to a particular use. As such, you’ll need to consider which use matches your desired cycling environment to get the most compatible cassette. In doing so, you’ll be one step closer to optimizing your bike for what you want it to do, and your rides will be all the more enjoyable for it.