How to choose the right bicycle cassette? Learn everything you need to know in our guide .
When will you need a new cassette? When will your chain slip on the cogs and start ruining your fun? Or maybe you need a new range of gears to help you tackle those steep climbs?
In this guide, we'll provide you with information about bicycle cassettes. So next time you need to change your cassette, you'll know a thing or two about finding the right model.
What is a bicycle cassette?
If your bike has a traditional external derailleur, it necessarily has a cassette. A cassette is a system of several or a dozen parallel sprockets. They can be mounted or threaded onto the freehub body. When you change gears, the chain moves up and down over these sprockets. Intricately designed teeth make it easier for the chain to jump between sprockets.
We have already written about the technical details, including the difference between a freewheel cassette and a freewheel, on our blog.
How important is a cassette on a bicycle?
Very much so. Your gear range can make the difference between a pleasant ride and a painfully difficult pedaling experience, depending on the terrain and how strong you feel. The chainrings in your cassette determine your gear range. Going uphill? Switch to a larger cog to reduce the "torque" needed to turn the rear wheel. You'll pedal faster, but it'll be easier. Want to overtake a friend? Switch to a smaller cog and you'll accelerate with fewer crank revolutions. As long as you don't mind pushing a little harder on the pedals.
How many gears does my bicycle cassette have?
The number of gears on a bicycle cassette is simply the number of sprockets it has. In practice, it ranges from seven to thirteen speeds. At the lower end of the price range, cassettes have fewer sprockets. At the higher end, 12- to 13-speed cassettes are increasingly becoming the default option on road, gravel, and mountain bikes.
How do I know which cassette to choose for my bike?
Choosing cartridges can seem overwhelming, but don't panic. Here's our checklist to help you decide.
Which bicycle cassette is compatible with your groupset?
Your bike's groupset is designed to work as a single system. Unless you're replacing the entire groupset, you'll need a cassette with the same number of speeds as your current one. If you have SRAM or Shimano , we have good news: The cassettes are interchangeable. If you have Campagnolo, you have to stick with Campagnolo .
What is the capacity of your derailleur?
A derailleur has a maximum cassette size, also known as capacity. A derailleur with a small cage and a large cassette of sprockets means the derailleur is overstretched. The chain then becomes too tight on the larger sprockets, risking chain or derailleur breakage. Want to increase your cassette size but don't want to change your derailleur? You'll simply need to replace the cage with a longer one. A longer chain will also be necessary.
What is the capacity of your drive system?
Your drivetrain has a maximum capacity. This is determined by the difference in teeth between the largest and smallest sprockets, and the largest and smallest chainrings. It's important to know if the cassette or any other drivetrain part needs replacing.
Here's how you can solve it.
(Number of teeth on the largest chainring - number of teeth on the smallest chainring) + (Number of teeth on the largest sprocket - number of teeth on the smallest sprocket) = Drivetrain Capacity
For example, are you using a 52-36 chainset with an 11-28 cassette? Here's how to find your drivetrain's maximum capacity.
- 52 teeth on the largest chainring - 36 teeth on the smallest chainring = 16
- 28 teeth on the largest sprocket - 11 teeth on the smallest sprocket = 17
- 16 + 17 = 33, i.e. the capacity of the drive system.
The larger drivetrain capacity provides a wider range of gear ratios. Perfect for hilly rides.
What size cassette do you need?
Cassette sizes consist of two numbers. The first number is the number of teeth on the smallest sprocket. The second number is the number of teeth on the largest sprocket. The closer these two numbers are, the smaller the steps between gears.
Road bike cassette sizes
The most common cassette size for road bikes is 11-32. Paired with a double or triple chainring, you'll have plenty of gears for most terrain. If you plan to do a lot of climbing, this can be easier. A cassette with more teeth on the largest chainring will provide you with more comfortable shifting, for example, in the mountains.
Mountain bike cassette sizes
The largest sprocket in an MTB cassette is larger than in a road cassette. Many mountain bikes typically have a 10- to 12-speed cassette. The largest sprocket can have 51 teeth, while the smallest sprocket can have 10 or 11. Typically, this is a single-chainring drivetrain.
Cheaper mountain bikes have a double or even triple crankset, which further increases the gear range but also allows for the use of smaller, less expensive cassettes. This allows for a versatile bike with little financial outlay.
Aggressive downhill riders who don't need to ride uphill because they're usually dragged down by a lift need just a few fast cogs in their cassette. A small cassette with 7 speeds or less and a solid short-cage derailleur will suffice. In the same discipline, some riders forgo the cassette and ride downhill with a single chainring front and rear.
How to calculate the gear ratio in a bicycle cassette?
Know your gear ratios to choose the right cassette for your terrain. This is easy to do. Divide the number of teeth on the rear sprocket by the number of teeth on the front chainring. So, for a 30-tooth rear sprocket and a 42-tooth chainring, the ratio is 0.71.
Why does this matter? This means that each pedal revolution causes the rear wheel to rotate 0.71 times. Gear ratios of 0.71 are considered low. Pedaling is easier, but reaching top speed will require a higher cadence.
A high gear ratio makes pedaling harder and more forceful. But it's easier to go faster. What does a high gear ratio on a cassette look like? Think of a 42-tooth rear sprocket and a 30-tooth front sprocket. This gives a gear ratio of 1.4.
Great for flat or downhill riding, especially sprints. But quite tiring on climbs or long distances. Planning a mountain bike trip? Make sure the lowest cassette-crankset combination provides a sufficiently low gear ratio.
Why are some cassettes so expensive?
It all depends on the materials and finish. At the lower end of the price range, cassettes are made of steel. This material is durable but heavy. The more you spend, the lighter they become. Some brands use more expensive materials like aluminum and titanium to reduce weight.
High-end cassettes available on our market are usually made of Cr-Mo steel + the largest sprocket is made of aluminum.
When should you replace your bicycle cassette?
Unfortunately, your cassette won't last forever. The teeth on the sprocket will eventually wear out.
If your chain skips under load while pedaling, it may be time to say goodbye not only to the cassette but also to the chain.
The easiest way to check cassette wear is to install a new chain. Install the chain, find a safe place (out of traffic), and try pedaling. Still skipping? Time for a new cassette. Take a closer look at the sprockets. You might even notice that the teeth look worse due to wear. If you ride mostly on flat terrain, the smaller sprockets will be noticeably different from the larger ones, with wider recesses. In extreme cases, the teeth can resemble rose thorns. Few "racers" achieve this feat.
How to replace a bicycle cassette?
Replacing a bicycle cassette with the popular HG system is easy. You'll need:
- The so-called chain whip
- Cassette attachment
- Adjustable wrench
- Gloves (optional, but recommended)
Remove the rear wheel and secure the cassette with the whip. Attach the cassette wrench and unscrew the locking ring in the opposite direction of the whip, which you're holding in your other hand. Slide off the old cassette and wipe the freehub body clean of dirt and dust, then install the new sprockets. All you need to tighten them is a cassette socket.
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