What Size Derailleur For Different Size Cassette? Explained!

Being a cyclist, you definitely have lots of things to look after in your cycle. And one of the most important things of such is the derailleur for your cassette. 

This one can be confusing to choose from at times. As there are a lot of variations in the size of derailleur. But before selecting one you must have sufficient knowledge about it.

What size derailleur for different size cassettes?

Choosing the right derailleur is quite crucial. Because this either makes the riding convenient or deteriorates it. You mainly consider the size of the cassette of your cycle for this. A small cassette requires a short derailleur and a medium requires a medium. Finally, a large one requires a large one.

This might seem enough for your concern. But actually, you have to continue reading as we have covered everything in detail.

So, just get started now!

What are Derailleurs And What is Their Operation?

Derailleurs are one of the important add-ons of a bicycle. This device can help the cycle to shift gears smoothly

What Size Derailleur For Different Size Cassette? Explained!

Source: BikeRadar

A derailleur can be installed on the front and rear wheel of your cycle. Choosing the best-fitted derailleur can make it way smoother for you to shift. 

The front derailleur keeps the chain in the correct position as required. On the other hand, the rear derailleur keeps the cage backward and forward.

As a result of this, derailleurs enable the chain to maintain the chain. In addition to that, this also protects the chain from getting snapped.

Thus, you can understand how important it is to install the right derailleur.

What Size Derailleur Do I Choose for The Cassette?

You already know now that derailleurs are important for your cycle. But choosing the right size of this is a must. 

Because an unfitted derailleur would not be compatible with your cycle. And even if it does, you would have many complications while riding.

As a result, you need to consider the right size of derailleur for your cassette. Take a look at our chart to have a clear idea about this.

Short CageSSShortShort 
Medium CageGSMediumMedium 
Long CageSGSEagleTriple

This is the chart that would give you a basic and very clear idea. So, you can just follow this one prior to making the purchase. 

Remember that the sprocket may come in a range of 11-32, 11-34, or 11-46. In that case, you would have to consider the long cage derailleur.

You may also want to match the Shimano cassette with the Sram derailleur. In that situation, you need to consider their sizes.

However, if you still have any confusion, you may ask for help before buying. The seller may help you out more than you could help yourself with this.

But get here an idea about the sprocket range first.

Sprocket 11-30

The 11-30 sprockets are the cassette with fewest teeth. There are 11 clogs which have teeth starting from 11 to 30 at max. You need the short cage derailleurs for this.

The best two short cage derailleurs that I would suggest you to have-

Sprocket 11-32

11-32 means there would be eleven cogs that would have a range of 11-32 teeth. These are generally compatible with short cage derailleurs. 

You can go for the before-mentioned ones. However, if you want something in budget SHIMANO Altus Rear Derailleur can be a great option too.

Sprocket 11-34

These are quite similar to 11-32. The teeth could be from 11 to 34. The medium cage derailleurs are compatible with these sprockets. 

I use this one with the SHIMANO Ultegra R8000 Mid-Cage Rear Derailleur personally.

But if you need something different SHIMANO Rear Derailleur can be an option.

Sprocket 11-36

11-36 sprocket means that the teeth of the cassette can go up to 36. You need to consider medium cage derailleurs for this.

You can pick up the before-mentioned medium cage derailleurs here.

Sprocket 11-46

These are the sprockets with the most teeth. These clogs have teeth from 11 to 46 at max. You would need a large cage derailleur for this one.

I’ve curated some of the best long cage derailleur in the following chart-

So, these are the derailleur sizes for your respective cassette sprockets.

Here’s a secret tip. You can hack your derailleur and increase it’s range. Check out this tweet about a step by step guide

Can I Change The Cassette?

You may think changing cassette is never an option. But you may sometimes need to do it too. A lot of people do it. 

You may want to change the cassette for the upgrade of gears. Sometimes, you may also want to change the cassette for your desired derailleur.

Because a particular derailleur might be the best for your cycle. There is a limited cassette size for every derailleur. 

The greatest number of teeth on the largest cog is frequently stated. In instructions, this is known as minimum sprocket max

As a result, for a derailleur with the highest cassette size of 30T, the cassette’s largest cog must not be larger than 30T.

If you are determined to change the cassette, you can contact a mechanic. We do not recommend you do this yourself as this might not be that easy.

Now, thinking about an ideal cassette for your bicycle? Don’t worry! Get on our favorite ones!

Hope this helps!

What Happens If I Choose The Wrong Derailleur?

Choosing the wrong derailleur can be really problematic for your cycle. You might not always feel it at first. But you would come across it sooner or a bit later.

The main problem you might be facing is with the gear. If you choose a bigger one then you would notice that the tension is more. 

For instance, you can not use Shimano gs instead of sgs

What Size Derailleur For Different Size Cassette? Explained!

Source: Bike Components

As a bigger derailleur would put way more tension, your chain might snap anytime. Even if the cycle chain does not snap, it would often fall off the line.

And this would be quite annoying to you, especially if it’s midway. 

However, a comparatively smaller derailleur would create other different issues. Firstly, it would enhance the amount of slack of your cycle chain. 

In addition to that, you would feel the cycle not riding too fast. This actually happens because of the clogged chain due to the derailleur.

That is, a comparatively smaller derailleur can be responsible for this issue. 

Other than these, you would also come across a few other problems too. Problems like gear shifting and gear skipping are common examples of this.

Can I Make The Unfitted Derailleur Compatible with The Cassette?

A lot of people wonder if they can fix the derailleur for the cassette. And some even try to do it also. However, you can not actually do it anyway.

Because there is no way you can change the mechanics of the chain or derailleur. If you even try to do so, you would end up making issues.

Because you may exercise something that would even deteriorate the condition of the chain. A primary example could be the slip of chain all of a sudden.

Thus, you must not ever try fixing the unfitted derailleur for the cassette.


Is it a must to match the derailleur with the cassette?

Yes, you need to match the derailleur with the cassette and this is a must. You have to consider the largest rear sprocket in order to match it. The size of derailleurs and cassettes come in a wide range that you already know. That is why you need to see and choose wisely.

Can I use Sram x5 for my mountain bicycle?

Yes, Sram x5 rear derailleurs are generally fine for mountain bikes. However, you may still need to look after a few things to confirm its use. Those factors are especially your rear sprocket and the gear system. If you think all these fit for it then go for it.

How much do I spend to buy a Sram x5 for my cassette?

Sram x5 rear derailleur is great in terms of its usefulness and effectiveness. As a result, these derailleurs could be a bit expensive compared to other ones. You may expect to spend around $50 at least to get one of these. However, the price may go up to around $70 depending on a few factors.

The Final Words

Now you know what size derailleur for different size cassettes to use! We believe you have certain ideas about your concern now.

Go through the chart properly prior to making the purchase. Because you might not be able to return the product once you buy it. Hope you find it helpful.

All the best!

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