During your mountain bike rides, the best derailleur allows you to easily ride uphill, ride downhill and tackle rough terrain.  Good quality derailleurs are designed to smoothly facilitate gear shifting even under load and make speed changes a breeze. Ultimately, this mechanism makes your rides smoother, efficient, and more enjoyable.

So, to fully enjoy your mountain biking, you must ensure that you invest in the right derailleur for your bike. Below, we’ve compiled a list of the top picks for the 8 best derailleurs in 2020. Choose your favorite option so you can fully enjoy and explore all the adventures that come with mountain biking. 

How To Choose A Derailleur – Buying Guide


Gear Number

When choosing the best mountain bike derailleur for your bike, you must know the gear or sprocket number to ensure you pick a compatible one. To understand your bike’s gear system, think of this – the number of sprockets at the rear and the number of chainrings at the front.

So for example, a bike with a double chainring set up and a 10 speed rear cassette is a 20-speed bike. It means that you can use any of the 10 sprockets of the rear cassettes with each of the two chainrings as you shift the gears during your bike rides. 

The number of gear or sprockets is dependant on your current setup. Unless you change the entire shifter with the gears, your gears on the derailleur must match that of the shifter that is currently installed on the bike. 

To get this concept visually, simply count the number of cogs on your cassette and that should equate to the gear number. And if for some reason, you have no way to determine your bike’s drivetrain speed, count the number of steps your shifter runs through. Then, take this value and add one – this should give you the number of gears that your bike’s drivetrain has.


Compatibility is perhaps one of the most important factors to consider when choosing the best mountain bike derailleur. Generally, you should avoid mixing groupset parts from different series and brands. So when you pick a front derailleur for mountain bikes, for example, it must match the rear derailleur, shifters, and cassettes, to ensure a proper fit.

Make it a point to purchase your rear and front derailleur as well as shifters from the same brand. However, sometimes, you may have a leeway, according to the brand you choose. For example, for older generation Shimano 8 and 9-speed mountain bike derailleurs, you can pair them with Shimano road bike shifters or vice versa. 

All Shimano 11-speed and 10-speed road bike components are also compatible respectively, no matter the series or model. The same applies to mountain bike components.

Cage Length

The cage length is the range of gears that you can have on your bike. A longer cage length means that your derailleur can take up more chain slack. A medium or long cage length can accommodate a wider cassette range of between 10 to 50 teeth, longer chainrings, or 2x mountain bike drivetrains. 

Medium and longer cage lengths also allow for longer biking trips with no hassle. A short cage length works for traditional road double drivetrains with at least 11 to 28-tooth cassettes.  Many downhill drivetrains also use short cages.

Weight of the Derailleur

The weight of your derailleur becomes extremely necessary if you are using it on a racing bike. A racing bike derailleur should be lightweight to make it easier to operate. However, the best mountain bike derailleur should also be lightweight to make your riding easier. But, this comes with a cost.

Typically, expensive derailleurs tend to weigh less whilst cheaper ones are heavier. This is because expensive derailleurs use materials that are not as abundant such as titanium for their pivots and carbon for the cages, to achieve the lightweight finish. So, you should only invest in one if you can afford it.

Adjusting system 

A derailleur that allows you a certain amount of adjustments makes your riding more comfortable. Therefore, when you are choosing one, this is a factor that you should certainly consider. Compared to other brands such as Campagnolo or SRAM, many Shimano derailleur models are designed with extremely user friendly adjusting systems.


A derailleur clutch is designed to increase the main pivot tension, resist force, and facilitate the movement of the cage. The tension that is provided by the main pivot is what holds the chain on the rear bike derailleurs in place. Increasing pivot tension and resisting force result in a reliable and noiseless drivetrain. In addition to providing noiseless rides, derailleur clutches also help to keep your chains in place. 

Bike chains can easily drop due to the changes in force or weight; however, having a clutch prevents this from happening. So it’s important to opt for modern derailleurs equipped with clutches.  Typically, most Shimano derailleur models are equipped with the Shadow Plus clutch system whilst SRAM derailleurs are equipped with Type 2 or Type 3 clutch systems.



Q: How Do I Choose A Derailleur?


To choose the right derailleur, you must know the key factors to look at. After all, if you don’t pick the right parameters, the derailleur may not work for your bike. The key factors to look at include;

  • The number of sprockets
  • The derailleur’s compatibility with your bike’s drivetrain
  • The cage length
  • The clutch system

Q: Are Derailleurs Universal?


No, derailleurs are not universal. Your mountain bike derailleur has to match the specifications of the original one on your bike and should be compatible with the drivetrain. Buying the same brand derailleur as well as matching the gear number ensures that you have chosen the right derailleur for your bike.

Q: Can I Use A 9 Speed Derailleur On A 8 Speed?


Yes, you can use a 9-speed derailleur on an 8-speed cassette. The main difference between a 9 speed and an 8-speed derailleur is the indexing. However, even if you can use a 9-speed derailleur on an 8-speed cassette, they must be of the same brand. Yet, an 8-speed derailleur cannot work on a 9-speed cassette.

Q: How Long Should A Derailleur Last?


Your derailleur should last you a lifetime or at least until you retire your bike. Whilst the pulley wheels normally wear out after 10 to 20 thousand kilometers, the rest of the derailleur’s mechanism continues to fully function for a while.

Q: How Often Should You Replace Derailleur?


Because they don't normally wear, there's no need to replace your derailleur. Many cyclists will only replace the derailleur if they frequently ride in rough terrains and harsh conditions. You can simply replace worn out jockey wheels after 10 to 20 thousand kilometers however because derailleurs are not very expensive, it is easier to replace the whole thing.

Globo Surf Overview

It is important to carefully choose the best derailleur for your bike, especially for mountain bikes. This is because they highly affect your overall riding experience. Through these derailleur reviews, you get to see how they can affect your entire gear systems and ultimately, how you ride. So take your time to choose the best mountain bike derailleur from the list above to ensure that your next biking adventure is as enjoyable as you hoped for.

More Bike Reviews:

Globo Surf
My name is David Hamburg. I am an avid water sports fan who enjoys paddle boarding, surfing, scuba diving, and kite surfing. Anything with a board or chance I can get in the water I love! I am such a big fan I decided to start this website to review all my favorite products and some others. Hope you enjoy!