The cogs at on the rear wheel of your bike together form the cassette. The cassette is an important part of the drivetrain that is responsible for rear-wheel drive. A cassette typically has multiple sprockets, each having teeth which mesh with the bicycle chain. Cassettes vary in size and the number of sprockets they have – sprockets also have a varying number of teeth.

You may have noticed cassettes having specifications such as 16-31T. The first number indicates the number of teeth on the smallest sprocket, the next indicates the number of teeth on the largest sprocket. The range of gears on your cassette combined with the number of teeth on your front chainring will give you gearing ratios to tackle different terrains efficiently/easily with your bicycle.


The wide range of cassette options can appear overwhelming at first glance. There are different combinations of sprocket gearings to suit different terrains and disciplines; for example, there are significantly different cassettes for triathlon bikes compared to mountain bikes or hybrids.

The kind of terrain you ride on primarily decides which would be the right cassette for you. If you live in a hilly area, you’ll certainly want to start with a larger than normal cog. Since doing this increases the gaps between cogs, bigger cogs aren’t ideal for riders who primarily ride on flat land. On the other hand, if you ride on flat roads, your ideal range should be higher gearing (smaller cogs).

The main thing to consider is the ratio of the gearing on the cassette. The smaller the difference between the highest and lowest number of teeth on the sprocket, the smaller the jump between gears; facilitating smoother gear shifts.

However, having closer-geared sprockets will usually decrease the size of the largest sprocket (one with more teeth) on the cassette or vice-versa. This may not be ideal for high cadence uphill or climbing scenarios.


MTB cassettes usually offer a wide range of gearing ratios for steep inclines and technical climbs that require more torque (bigger gears) to long descends that require lower cadence and more power (smaller gear). The larger number of gears means that the biggest gear can have a bigger number of teeth making it easier for challenging climbs while reducing the magnitude of the jump between each gear. 

Most MTB bikes these days feature 8-speed cassettes all the way to 12-speed cassettes. Cheaper, low budget bicycles use 7 or even 6-speed cassettes.


Road cassettes can feature 9, 10 or even 11 sprockets that have smaller gearing jumps that allow for smoother shifts and optimal cadence. Road cassettes usually feature a 12T as the highest gear and between a 25 to 32T as the lowest gear.

If you do a lot of hill climbing or struggle with it, a cassette with a lower ratio largest sprocket (one with more teeth, such as 27 or more) may be beneficial. It will allow you to keep a higher cadence throughout the climb ensuring ease of climbing and consistency.

When selecting a cassette for your road bike, ensure your derailleur can accommodate the largest sprocket


You’ll know when your cassette has worn out, it makes its presence felt. A loud and rough shift along with frequent chain slippages are some symptoms of a worn-out cassette. You may also look at changing your cassette depending upon your needs such as wanting to go faster on flat sections or wanting to climb better.

Cassettes are hard-wearing components they often last very long, anywhere between 2,000 to 4,000kms is what you can expect. That is if you take care of it properly. A cassettes life also heavily depends upon on chain maintenance. A poorly kept chain can get worn out and can expand fast. This, in turn, will cause the teeth on your cassette sprockets to wear out fast and deliver imprecise and notchy shifts.


MTB cassettes are made of highly durable and fairly lightweight materials as MTB’s are exposed to all terrains and weather conditions. Cheaper cassettes are made of steel that is highly durable and hard-wearing but at the same time quite heavy.

More expensive high-end cassettes for both MTB’s and road bikes are made of lighter metals such as Titanium and Aluminum; they do however wear out faster as they are softer metals. In competitive cycling riders usually, opt for these kinds of lightweight cassettes as they save on weight. Especially since it is a rotational mass that plays a big role in resistance.

There are also cassettes in the market that have a mix of both lightweight, less durable and heavier, more durable materials. Larger gears with more teeth are made with lightweight materials and the smaller gears with fewer teeth are made with heavier but more durable material.


With the introduction of index shifting by Shimano, cross compatibility got a little more complicated as SRAM used their own 1:1 actuation whereas Shimano and other brands used higher ratios. This basically meant that derailleurs of one brand couldn’t be used along with shifters of other brands. In terms of cassettes, things were further complicated with the evolution of 11-speed cassettes from 6-speed cassettes.

The introduction of 8 speed systems only worked with an increase in rear hub width from 126mm to 130mm to accommodate an extra sprocket. After that, the spacing of the sprockets was reduced to allow for more sprockets to be fit in without increasing hub width.

Before buying a cassette always check compatibility between the other components on your drivetrain and your new cassette. Most brands such as SRAM and Shimano are cross-compatible. However, it’s best to check the compatibility at all times before purchase.


If you need that additional bit of speed on flats or want to improve your climbing capability choosing the correct cassette is critical. The correct number of teeth, the number of gear options and the material of the cassette are important deciding factors to suit your riding environment and riding style. Checking on compatibility is critical for efficient shifting.

A cassette installation is a quick process that only requires a chain whip and an adjustable spanner in most cases. It can be done at home with the correct tools or at your favorite local bike shop.

How helpful was this article?

Click a star to rate.

Average rating 4.8 / 5. Vote count: 5

Shucks. We're sorry this post was not that useful

How can we improve this post for you?

About the Author

Shaun George

WHAT I LOVE ABOUT CYCLING I'm an avid mountain biker and I like riding fast and flowy singletrack. As I keep riding, I continuously work on honing my riding skills. I like to ride whenever possible, especially with friends. I also like to influence folk into getting to ride more often. Working on bicycles has also been a keen interest of mine for quite some time. DISCIPLINE: Mountain biking and Road biking CURRENT BIKE: Merida One Twenty 9.600 & Specialized Allez Elite DSW DREAM BIKE: Santa Cruz 5010

View All Articles