Bike cassettes - explained
Cassettes are one part of the drivetrain system on a bike.
A cassette is a series of gears located on the freehub on the rear wheel of a bicycle which allows the rider to ride in easier or harder gears. By changing from one gear on the cassette to the next, you are changing the ratio of the gears and increasing or decreasing the resistance for the rider.
Understanding how a cassette works and how to choose the right cassette for your discipline of cycling is critical and something which can get you the best out of your bike.
In this article we will look into the different types of cassettes, what a cassette is made up of and what to think about when selecting a cassette for your bike.
What are the different types of cassettes?
Road Cassettes
Road cassettes are designed for use on road bikes and generally have a narrower range than the cassettes used on mountain and gravel bikes. The narrower range allows for smaller changes in the ratio of the gears between two gears on the cassette, which makes the bike ride smoother and more comfortable to ride on the flat or rolling terrain.
Road cassettes have gone up in size over the years, increasing from 5 speed to 12 speed over a few decades. As the size of the cassettes have increased so has the ratios. Road cassettes can now range from 11-23 to 11-34 (11 being the number of teeth on the smallest gear on the cassette and 34 being the number of teeth on the biggest.
Mountain Bike Cassettes
Similar to road cassettes, mountain bike cassettes have also increased in size as technology has progressed. Mountain bike cassettes can be found in much bigger ranges with bigger jumps between gears, this is because of the terrain and conditions that mountain bikes are used in compared to road bikes. A lot mountain bikes now have only one chainring on their chainsets. Due to only having one chainring the cassette needs to have an even bigger range – some mountain bike cassettes are 10-52!
Mountain bike cassettes can now also be found in 12 speed (meaning there’s 12 gears on the cassette).
Gravel Bike Cassettes
Gravel bikes have become very popular in the last few years as they fill the gap between road and mountain bike riding. Their tyres, clearances and braking system are designed at being in between road bikes and mountain bikes and their cassettes are no different.
Gravel bikes can be ran with one or two chainrings on their chainsets, therefore they have to have cassettes with both big ranges and more standard ranges.
Cassette Components
A cassette is made up of three different parts, these are:-
1. Gears – these are the obvious parts of a cassette, the individual gears on a cassette come in different sizes and are aligned in size order with the smallest gear at the bottom of the cassette and the biggest gear at the top.
2. Spacers – these are positioned in between the gears and the width of them is critical. This is because the gap between the gears has to match the distance the rear derailleur moves when it indexes one shift. Some spacers are attached to the sprockets, others are separate spaces and some cassettes are a combination of the two.
3. Lockring – the lockring is used to fasten the cassette in position. It screws into the freehub and locks against the cassette. It is tightened using a lockring tool.
Cassette Compatibility
This is where things can get confusing!
The first thing to think about when buying a new cassette is what speed and brand cassette you require and what freehub it’s being fitted to. This is because different speed cassettes can come in different widths, for example an 11 speed shimano cassette is 1.85mm wider than a 9 speed shimano cassette so if you wanted to fit a 9 speed cassette on a Shimano HG freehub, you’d need to fit a 1.85mm spacer on the inside of the cassette for it to be compatible.
Shimano and SRAM used to be able to be mixed and matched, however this has now changed with the latest SRAM equipment so care has to be taken when attempting to mix and match between brands. Campagnolo can not be mix and matched with Shimano or SRAM as they have their own freehub design, meaning only a Campagnolo cassette will fit on a Campagnolo freehub.
Cassette Costs
The cost of a cassette can massively vary depending on what brand and range of cassette you buying, what speed the cassette is and what material the cassette is made from.
The cost of a cassette can range from £18 for a 9 speed Shimano Sora cassette to £250 for a 12 speed Shimano Dura Ace cassette – this is just taking into account the Shimano range.
A cassette is a wearable part and will need replacing periodically. The best thing you can do to help the lifespan of your cassette is to frequently check your chain for wear. A worn/stretched chain will quickly worn your cassette down.
Here’s an article from the Bicycle Maintenance Guide on ‘How to Check your Chain for Wear‘.
Click on the links below to learn more about the bicycle maintenance guide app
