A Guide to Bike Cassettes: Top Things to Know Before Buying Bike Cassettes

Bikes may seem simple at first glance, but there is a lot more going on than just a pair of wheels and a frame. The majority of bikes sold and ridden today are geared, with the rear derailleur shifting the chain up or down a set of sprockets attached to the rear wheel. This is what is called the bike cassette.

Cassettes come in different sizes and designs and suit different types of bikes. And they determine among other things how easy the bike is to ride on different types of terrain. Let’s delve deeper.

What Exactly are Bike Cassettes?

A bike cassette is the cluster of sprockets located on the rear hub and attached to the freehub body. The number of sprockets or cogs can vary between different bikes, ranging from 5 to 13 separate sprockets. This determines the number of ‘speeds’ or gears the bike has. Sprockets are spaced precisely relative to one another and help with smooth shifting. Generally, the more sprockets a cassette has, the less distance the chain has to travel from one sprocket to the other.

The number of sprockets has been steadily increasing, with 10 and 11-speed cassettes now the norm in both mountain and road bikes. These provide a good balance between gearing range, weight, and price. Range allows riders to change pedaling cadence, or revolutions per minute, to get optimal efficiency. This will also depend on the number of teeth in each sprocket. Riding the bike in a bigger sprocket and one with more teeth means easier climbing (usually at a higher cadence), and with the chain in a smaller sprocket and a lower tooth count, you can build speed for a descent or on the flats by pedalling harder. What’s to remember is that the spread of gears is different in different types of bikes. And you’ll need a compatible chain and derailleur specifically for the cassette. For instance, you can’t use an 11-speed chain on a 10-speed cassette.

Types of Bike Cassettes

Cassettes can be divided into two broad groups – those used on road bikes, and those used on mountain bikes. Since the two categories of bikes are meant for different types of terrain, there will also be some significant differences, especially with tooth spacing and gear range.

Road Bike Cassettes

Road bikes have cassettes that are typically smaller than what you’d find on a mountain bike, meaning fewer teeth and a smaller jump between gears. The smallest sprocket often has 10, 11, or 12 teeth, whereas the biggest is anywhere between 22 and 34 teeth. Again, the bigger the difference between the tooth count, the bigger the gearing range. For instance, an 11-speed cassette marked as 12-25T will be harder to ride on steep climbs than an 11-34T cassette. But the shorter spacing will provide smoother gear changes in paced riding on flat roads.

When shopping, there are 3 bigger brands to look for. Popular Shimano 11-speed cassettes for road bikes include the Dura-Ace R9100 (the newer R9200 is 12-speed), and the older 105 7000, with the newer version having one more sprocket and wireless shifting. Here we can also mention the Ultegra R8000. SRAM has the PowerGlide PG1170 and the gravel-specific XG 1190. Italian bike parts specialist Campagnolo has the Chorus and Potenza lines of 11-speed road cassettes. Worth mentioning is that SRAM and Shimano cassettes are interchangeable, but both are incompatible with Campagnolo components.

Mountain Bike Cassettes

Since mountain bikes are meant for more varied terrain, the gearing and sprockets are bigger than on road bikes. The smallest sprockets start out with the same 10, 11, or 12 teeth (newer versions have 9), but the biggest can go up to 52 teeth in current variants. It’s not uncommon to find 10-52T cassettes such as the SRAM Eagle and similar gearing to the 11-50T 11-speed cassettes in the Shimano Deore lines. Campagnolo steps things up with the 13-speed Ektar series and some interesting gearing options. Since there is more than enough range with huge sprockets, mountain bikes now have single chainrings up front, so there’s lower weight, no need for a front derailleur, and crisper shifting.

What to Look for

Cassettes, like all bike essentials (link), come at different price points. Generally, you’re getting your money’s worth in terms of build, weight, and materials and how the cassettes perform, how they gel with other drivetrain parts, and how long they last (with the proper maintenance, that is). There are more savings if you don’t absolutely need the newest cassette lines but can choose tech from a year or two back that will work perfectly fine. Sure, they might be a few grams heavier, but that’s money that can be used elsewhere. Lesser known, but still quality brands like microSHIFT and SunRace produce decent, if not comparable, cassettes in a range of gearing options at considerably lower price points.

The last thing to remember is to check for freehub and drivetrain compatibility before buying. For example, while an 11-speed cassette can work with 12-speed shifters, there might be performance issues like chains slipping, and more effort required in gear changes.