Freewheel vs cassette: how to choose the best for your bike

A freewheel, also known as a block, consists of either a single sprocket or a set of sprockets mounted on a body containing an internal ratcheting mechanism and mounted on a threaded hub. It screws directly onto the rear wheel of your bike and the mechanism that locks when you pedal forwards - forcing the wheel to be driven by the train. It spins freely when you're simply cruising along, i.e. not pedalling or going backwards.

A cassette is the modern alternative and has quickly overtaken the freewheel. Cassettes have a series of straight splines forming the mechanical connection between the sprockets and the cassette-compatible hub, called a freehub which contains the ratcheting mechanism. The entire cassette is held on the hub by way of a threaded lockring. Some cassette systems from the end of the 1980s and the start of the 1990s used a threaded small sprocket to hold on to the larger splined sprockets. Cassettes resemble freewheels when installed but differ when removed as they don't contain a freewheel's internal ratcheting mechanism.

To make the right choice, you need to know the difference between a freewheel and a cassette, so let’s take a look and compare.

The freewheel is a block of cogs that screws directly onto threads on the rear wheel. There is no need for it to be mounted onto a hub. It typically comes with anywhere between 1 to 7 cogs, and it is rare to find a freewheel on a modern bike. You do however find them on some new single-speed bikes. A freewheel that comes with 1 cog can also come fixed, meaning that you always have to be pedalling unless the bike is stationary.

The freewheel is, as described above, a block of cogs that the chain sits on directly that drives the wheel. The ratchet system is built into the block, meaning the wheel can just have a set of threads the block screws onto.

However, a freehub has no cogs; it is the hub on the rear wheel that the cassette sprockets slide onto. This part has a ratchet system that locks when the cassette is driven by the chain, causing the wheel to spin.

Since their introduction in the late 1970s, cassettes have been used on a number of bicycles, starting at the high-end, and over time, have also become available on less expensive bikes. Today the vast majority of derailleur bicycles use this newer design. On a cassette, the cogs slot onto the cassette body one by one. They are then held in place with a locking nut. They can range from 7 cogs all the way up to 12 speeds on high-range bikes. Generally, these come fitted on mid to high-range bikes, allowing the rider more flexibility over the terrain and giving them more speed options.

Usually, an 11,12 or 13-tooth small sprocket and 21 and 32 teeth large sprocket. This is because a road bike requires smaller jumps between gears than a more robust model like a mountain bike. The majority come with a 12 to 25-cassette paired with a compact or standard chainset for most flat cycling terrains. If the bike is used for hill climbing or you struggle with inclines, a lower ratio largest sprocket (27 or more teeth) will be better for spinning than grinding. When choosing, ensure you know what kind of sprockets your derailleur can handle. A longer cage rear derailleur requires larger sprockets as more chains will be needed around the more significant number of teeth. A small derailleur with a large sprocket runs the risk of overstretching and may lead to slackness.

Due to the wide variety of terrains and gradients tackled with off-road riding, these require an extensive range of sprocket sizes. The development of the 11,12, and now 13- speed cassettes was pivotal for mountain bikes. More sprockets mean that the biggest gears have more teeth, making better gears for touch climbs and reducing the gap between each gear. This means mountain bikes no longer need the triple chainset to minimise clutter, weight and mechanical issues.

A freewheel has fewer gears and is better suited for casual riders who don’t require a more extensive selection of gears available from a cassette. It offers better coasting, allowing you to rest your legs, and if done correctly, can be useful when climbing hills and easier coming down. At the same time, because of the option to coast, the freewheel is not as good when wanting to get a workout from a bike ride. They can also lead you to lose your pedal stroke, which can mean losing pace on flat terrain. Cassettes are made up of individual pieces that are less bulky, thus allowing them to be a lower weight than a freewheel. More tools are required to change a cassette. However, a freewheel that has been on a bike for a while can seize and be very difficult to remove, whereas a cassette does not have this issue. A cassette is the better option if you find yourself riding on various terrains and at varying speeds.

To identify which type you have on your bike you will need to start by removing the rear wheel from the bike. Then spin the cogs backwards by hand, if everything apart from the axle moves, then it is a cassette. If part of the block is stationary when the cogs move, then it is a freewheel.

If your bike has a freewheel or you choose one that comes with one, it’s easier and cheaper to stick with a freewheel and if you choose a cassette - it’s easier to stick with a cassette. It’s difficult and can be quite costly to swap, in most cases requiring a new wheel, gear shifter and chain. Furthermore, you’ll need the tools for both a freewheel and cassette in order to switch between the two.