Whether you’re heading out to your local park or up into the Cascades, you count on your mountain bike to provide you with performance and power. Much of your control and capability stems from the ability to shift to a higher or lower gear to meet the demands of the specific situation, which requires the use of a mountain bike derailleur.
If you’re in the market for a new derailleur, it can be hard to choose the right replacement. We’ve ranked the nine best mountain bike derailleurs out there to help make it easier for you. We also take things farther by providing individual reviews on each of the nine derailleur models, and then we wrap up with a buying guide that will help you better understand what to look for when buying one. So, without further ado, let’s dive into the head-to-head comparison.
Best Mountain Bike Derailleurs - Our Top Picks
Shimano XT RD-M8000
- Shimano Deore XT RD-M8000 SGS 11-speed rear derailleur.
- Item Package Length: 15.6 cm
The top-rated derailleur on our list is the Shimano XT RD-M8000. It offers steel and aluminum construction for robust durability and performance in all conditions, but without the price tag that comes with carbon fiber models. Like most of the mountain bike derailleurs on our list, this one is a rear-mounted option, so it cannot be used with front-mount setups. Also note that the GS is a medium cage and the SGS is a long cage to suit your needs.
The derailleur comes with a two year warranty from the manufacturer, and it features the new Shadow design, which also reduces the effort needed to shift by 20% according to the manufacturer. Note that this model does come with a link installed if you need one, but it can also be installed on your bike directly without the link if you’ve got a more updated model. The stabilizer is very easy to adjust, and helps eliminate chain slap when engaged.
SRAM GX Eagle 12-Speed Rear Derailleur
- Experience precise and reliable shifting with the thoughtfully designed cage architecture of the GX Eagle Rear Derailleur.
- Enjoy the flexibility of using both 10-50t and 10-52t cassettes with the backwards compatible design.
Our second mountain bike derailleur pick is the SRAM GX Eagle. It’s designed for 12-speed setups, and features a long cage. It can accept cassettes ranging from 10 to 50t, and it also features an X-Actuation pull. Note that this model is also made from aluminum (cage) and steel (pulleys and springs) for better durability without the higher cost that usually goes hand in hand with carbon fiber.
This derailleur features a type-3 roller bearing clutch for smoother operation and an improved torque curve, combined with quieter use. It includes a cage lock feature, and the X-Actuation capability ensures sharp shifting across the entire range. Ghost shifting is impossible thanks to the X-Horizon feature, and shifting force is also reduce, although not as much as with the Shimano model we featured above.
Shimano XT RD-M786 GS Shadow Plus Rear Derailleur
- Stabilizer switch to reduce chain slap
- Low profile Shadow design
Featuring the low-profile Shadow design that delivers reduced shifting force and a slimline profile, the Shimano XT RD-M786 GS Shadow Plus is an excellent choice for anyone looking for a new mountain bike derailleur. This model is designed for 10-speed setups and mounts to the rear wheel. It also includes a link, although it is direct mount capable.
The XT RD-M686 derailleur offers a unique stabilizer switch design that can reduce chain slap while riding, as well as a new clutch system that comes from the XTR Shadow Plus to deliver smoother performance and better reliability. You simply need to increase the spring tension by flipping a switch, which also helps reduce the chance of dropping the chain. Note that this is an all-aluminum model with direct cable path routing. Maximum chainwrap capacity is 35t.
SRAM Force 22 Rear Derailleur
- Carbon fiber and aluminum construction
- Cartridge bearing pulleys
One of just two carbon fiber derailleurs on our list, the SRAM Force 22 is designed for use with rear-wheel setups. Only the outer cage is made from carbon fiber. That’s a nod toward weight saving. The inner cage and outer links are made from aluminum, while the inner link is made from magnesium. This model features a short cage length, and it is backed by a two-year warranty from the manufacturer.
The SRAM Force 22 derailleur is designed to provide very smooth performance without any variance or issues. It is for use with 11-speed bikes, and it features 1:1 Exact Actuation technology derived from the Red group set. It also offers the AeroGlide pulley system, a new barrel adjuster with micro-adjustment capabilities, and will not disappoint when it comes to performance and reliability.
Shimano Acera Mountain Bike Rear Derailleur
- Double Servo mechanism enables the rear derailleur to move in an optimum path
- Versatile performance and wide compatibility
This mountain bike derailleur is a little different from the previously reviewed Shimano model. It offers only 8 speed performance, and it is available in black and silver. It’s designed for placement on the rear of the bike, and it features Smart Cage technology, as well. Note that this is designed for use with HG sprockets and it attaches directly to the bike. It does not come with a link.
The Shimano Acera derailleur offers Advanced Light Action to ensure smooth gear changes at all speeds and under all conditions. The link pivot bushings reduce friction to lessen the force needed to shift, and the cage offers both lightweight construction and excellent strength. It also features a long cage to support a wider range of gearing choices.
Campagnolo CPY S Record FD-15 11S Derailleurs
- 11-speed double road race front derailleur
- Interacts with crankset for speed and precision
This is the only front derailleur to make our list. It’s designed for road racing, not for mountain biking, and it is compatible with 11-speed setups. The outer cage is made from carbon fiber to save weight and deliver good strength, while the rest of the derailleur is made from aluminum and steel. It should be noted that the cage has a graduated curvature that is designed to help speed up shifting and improve precision.
Because this is a road racing derailleur, it is not recommended for mountain biking use. While it is lightweight and strong, it will not offer the right capabilities. However, if your bike pulls double duty as a racer and you don’t mind swapping drivetrains between setups, it could work for you.
Shimano Deore 9-Speed Mountain Bicycle Rear Derailleur – RD-M591
Another entry from perennial favorite Shimano, the RD-M591 is an excellent rear derailleur for those with 9-speed bikes. Note that this derailleur is only compatible with 9-speed HG cassettes from Shimano, as well as 9-speed mountain bike shifters and 9-speed chains. Each link pin bushing is coated in fluorine, and the derailleur offers 34t minimum low gearing for proper function.
It weighs in at just 299 grams, and delivers smooth, crisp performance combined with excellent durability and performance. If you’re looking for an affordable derailleur for a 9-speed setup that doesn’t skimp where it counts, this could be a good option.
SRM X01 Eagle 12-Speed Rear Derailleur
- Updated cage provides better chain retention and more precise shifts
- Comes in X01 Eagle master colorway as part of Eagle Colorsystem
Crafted from forged aluminum and imbued with a titanium spring, the SRM X01 Eagle is an outstanding rear derailleur that offers durability and performance. The Eagle length cage, X-Actuation pull, and 10 to 50t gearing capabilities add to the value it delivers. It also delivers a wide gear range across 12 cogs, features a roller bearing clutch, and features a large upper pulley to maintain better chain gap consistency across the cassette. Cassette volume is addressed thanks to the Exact Actuation technology, which also helps ensure that each shift requires the same amount of cable pull.
SRAM GX Bicycle Rear Derailleur with 1 x 11 Speed Long Cage
- GX provides the widest 2×11 gear range available
- The GX 2×11 rear derailleur provides incredible shifting speed and precision
The name really does say it all with this one. This mountain bike derailleur is designed for 11-speed setups, and it is a long cage model. It features a roller bearing clutch, as well as cage locking technology. The 12-tooth pulley wheels offer reduced climbing fatigue, and shift force and ghost shifting are both virtually eliminated by the X-Horizon design. The bearings are completely sealed to keep out dirt, water, and other contaminants, and the high-quality construction materials ensure durability and longevity even through harsh use.
There you have them – nine of the best mountain bike derailleurs on the market. As you can see, there’s something for just about every riding preference, budget, and need. Of course, if you’ve never purchased a derailleur before, or you’re changing things up from a different style of riding, you probably still have some questions. We’ll address those in our buying guide below.
Choosing the Perfect Mountain Bike Derailleurs
Maybe you’re looking to change your riding style. Perhaps you’ve managed to break your old derailleur. Whatever the case, you need to compare your options and make an informed decision. That can be pretty challenging thanks to the wide range of different options on the market, and if you lack a lot of experience, it only gets more difficult. The good news is that it doesn’t have to be a chore. Understanding a few key factors will help you find the right mountain bike derailleur with less time spent and less hassle. We’ll break down everything you need to know right here.
Number of Gears
One of the most critical considerations when choosing a new derailleur is the number of gears it is designed to work with. This will hinge on things like the type of bike you have, the type of chain you have, and the type of cassette that you’re using. Simply put, a 10-speed derailleur will not work with a 9-speed cassette, or a 12-speed chain. Each of the components in the system must be the same.
With that being said, if you really want a particular derailleur and it’s not compatible with your current setup, you can change that. You can purchase new shifters, a new chain, and a new cassette and give your mountain bike a major facelift. However, that’s a lot of work, and for most people, the better option is to simply stick with what you had previously.
Derailleur Compatibility
If you were paying attention to our list of the best derailleurs for mountain bikes, then you noticed that all but one of them were for the rear of the bike, not the front. When replacing your rear derailleur, you do need to make sure that you’re getting something that is compatible with the front derailleur and with your shifters. This goes beyond buying a model designed for the number of gears your bike has, though.
Most rear derailleurs are very specific and must match the chain, cassette, shifters, and front derailleur. Usually, this means purchasing one from the same company that made your other components. You will also likely need to purchase a derailleur from the same line as the rest of your components – the SRM Eagle, for instance, or the SRM Red group set.
Your only other option, as mentioned in the section above, is to do a complete overhaul on your entire drive system.
Cage Length
You will have noticed that there were short, medium, and long cages listed with our rankings of the top derailleurs. What does that mean, though? It applies to your chainrings. If you have a triple chainring, then you want a long cage. If you have a double chainring, then a medium cage is better for you. Finally, if you have a single front chainring, then you’ll need a short cage.
Materials
A wide range of different materials can be used in making mountain bike derailleurs. In our list alone you saw carbon fiber, steel, aluminum, titanium, and magnesium. Each of these has something different to bring to the table:
- Aluminum – Lightweight, strong, and durable, aluminum can be used for just about every part of a derailleur except for the springs in most cases. Forged aluminum and aluminum alloys offer outstanding performance and durability, but for less money than some higher-end materials.
- Steel – Steel is very strong and very durable, making it a great choice. However, it can also be pretty heavy, which means that when it is used in derailleur construction, it’s a little limited. Usually, only components that need high-tensile strength are made from steel, such as cogs and springs.
- Carbon Fiber – One of the newer and most popular materials in the industry, carbon fiber is super light and very strong. It’s also the most expensive option out there, which is why only two of the models we listed are made from it. While it can provide superior performance and weight reduction, the cost alone often puts it out of reach for many riders.
- Titanium – Titanium is very, very strong and, thus, exceptionally durable. You’ll find it used in a number of different ways within derailleurs where strength and resilience are needed. It is also relatively light, although not as light as carbon fiber.
- Magnesium – Magnesium is light but strong, and is sometimes used for spring manufacturing. Only one of the derailleurs on our list uses this metal in its makeup, though.
Ultimately, there is no perfect construction material. Each is a tradeoff. Some are light but weak, while others are strong but heavy. Carbon fiber is light and strong, but it is expensive. You will need to find the right combination of materials to deliver a durable, reliable derailleur that fits your needs and your budget. However, there’s something on our list for just about everyone.
Weight
Weight may or may not be a big consideration for you, particularly when we’re talking about just a few grams. However, some riders put a lot of stock into weight reduction, and are willing to pay lots of money for the lightest components on the market. Our opinion is that weight doesn’t really make much of a difference unless you’re racing.
Brand Choices
Let’s face it. You’re more than a little limited when it comes to derailleur brands. There’s Shimano, and there’s SRAM. Campagnolo is also around, but the Italian company’s mountain bike-specific offerings are few and far between, although we did include one derailleur on our list. Most Campagnolo products are focused on racing, rather than mountain biking performance.
Is there a better brand? It’s actually more about personal preference than it is about quality or performance. SRAM is supposed to provide a snappier shifting performance according to some people. Shimano has a number of other attributes. Again, it is more about personal preference in terms of brand adherence. However, you cannot usually mix and match derailleurs and other system components, so even if you want to try out Shimano, if your bike is outfitted with SRAM components, then you’ll need the appropriate SRAM derailleur. Either that, or you’ll need to complete a drivetrain overhaul.
Clutch Considerations
Each mountain bike derailleur we covered includes some type of clutch. This is an innovative solution to the challenge of keeping the chain on the gears through hard use, riding over bumps, and encountering other obstacles while on the trail. The clutch helps keep tension on the chain to keep it firmly seated, but there cannot be too much tension, or shifting would become a major issue.
You will find a very wide range of clutch technology out there. Shimano’s most famous is the Shadow Plus clutch, which can be found on several of the derailleurs we listed. SRM has type 2 and type 3 clutches. Other companies have yet other designations and technologies. When comparing your options, you want to look for capabilities like clutch locking, which makes changing wheels simpler, as well as shifting ease and tension capabilities.
Tuning and Adjusting
All derailleurs will need some amount of adjusting and tuning to get them just right for your riding preferences. Each is different. SRAM is reputedly somewhat challenging to tune and adjust, while Shimano has a reputation for being less time and labor intensive.
Should You Go Electric?
Before we even talk about electric shifting, let us be clear – all of the derailleurs covered in our list are mechanical, not electrical. Electric shifting is something relatively new, and it offers greater precision than what mechanical shifting can offer. That’s good news for a lot of riders. It has also spread from the world of racing into mountain bike riding.
With all of that being said, electric components are very expensive, with a minimum starting point of over $1,000. You will also need to rebuild the entire system, as electric derailleurs only work with electronic shifters. However, if you’ve got the bankroll and really want to try out the newest of the new, you’ll find electronic components available from both SRAM and Shimano. For the rest of us, mechanical shifting will be the way to go for some time.
Conclusion
In the end, the right derailleur for your mountain bike is likely going to be an exact replacement for the one you’re replacing, or will be compatible with your existing equipment. Remember that in most cases, mixing and matching is not possible. You’ll need to use the same brand for your derailleur as for your shifters, for instance, and often you’ll need to shop from within the same production line. However, it is possible to completely rebuild your drivetrain from the ground up if you really want to try out another brand or another line from your current brand.