12 Best Mountain Bike Derailleurs 2021 [Top Brands Reviewed]

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Bike derailleurs are appropriately named after the French word for ‘derail’. Their function to derail the chain from one gear to another is very important for serious cyclists, especially on uneven terrain. If you are a mountain bike rider looking to replace a broken derailleur or upgrade for better performance, then this article is for you.

Finding the right derailleur requires a good amount of technical knowledge, which many of you may not have. You may be thinking about things like cage length, tooth capacity, etc. Well, in this article you will find a comprehensive guide to buying rear derailleurs for mountain bikes. You will also find detailed reviews of what we found to be some of the finest mountain bike derailleurs.

Buying Guide: Mountain Bike Derailleurs

1. Compatibility (Brands)

The derailleur market is dominated by just two brands, SRAM and Shimano. So we will mainly talk about these two. Although, there are others such as Campagnolo, Rotor, Micro shift, etc. As a rule of thumb, it is not a good idea to mix and match components of different brands. While cassettes, cranks, and chains can be interchanged, shifters and derailleurs cannot. Each brand generally uses a unique cable pull ratio which is the distance moved by a derailleur for 1 mm of cable movement. Technically, you could put together a hybrid Sramano drivetrain but the shifting will most likely be very poor. It is simpler to just stick to one brand.

Various derailleurs

Image: Various-derailleurs

2. Compatibility (Groupset Components)

Even within the same brand, it might not always be possible to mix and match components from different generations or combine mountain and road bike parts. First of all, you should determine the number of gears available in your current groupset. To do this, you could either count the number of cassette cogs or count the number of steps run by the shifter and add one. Now you can pick a derailleur based on compatibility. The following points categorize compatibility by the manufacturer and are applicable for both derailleurs and shifters.

(i) For Shimano mountain bike derailleurs:

  • All 12-speed MTB components are inter-compatible.
  • All 11-speed MTB components are inter-compatible.
  • All 10-speed MTB components are also incompatible.
  • Present 9-speed MTB components are compatible with earlier 9-speed MTB and road components.

(ii) For SRAM mountain bike derailleurs:

  • All 7, 8, and 9-speed road and MTB components are inter-compatible.
  • All 10-speed road and MTB components are inter-compatible.
  • 10 and 11-speed MTB components are not inter-compatible (but road components are).
  • 11 and 12-speed road and MTB components are not inter-compatible, except for eTap batteries in electronic systems.

3. Electronic Derailleurs

Unlike mechanical derailleurs that use a cable to move the cage, electronic derailleurs have a small motor and gearbox inside for cage-actuation. This motor is controlled by electronic signals sent by the shifter. Electronic shifting has some clear advantages over mechanical shifting. Firstly, the shifting is faster, smoother, and much more reliable. Also, since you are essentially just pressing buttons, it requires less effort than pulling on a lever. Sometimes you even have the option to customize the controls using an app. Electronic components also require a lot less maintenance.

Electronic derailleur

Image: Electronic-derailleur

However, before upgrading to electronic shifting, there are some things you should keep in mind. The cost of such a set is typically very high. Replacement parts are also expensive but you might not need this too often. Also, there is the chance that your battery might run out mid-ride, even though a full charge can easily last you hundreds of miles. To avoid this, make sure the battery has enough charge before long rides. You can also carry spare batteries. Another downside is that technical problems are difficult to diagnose and repair, so you might need some professional help.

4. Cage Length

All derailleurs come in one of three cage lengths – long, medium, and short. Which one you should get depends on the range of gears you have on your bike. Generally, for super-wide cassettes (e.g. larger than 10-42t) or a triple chainset, you will need a long cage that can take up the extra slack in the chain. If you are running a 1× or 2× drivetrain with a regular-sized cassette you should use a medium cage derailleur. Short cages can only be used with 1× drivetrains and smaller cassettes.

Cage lengths

Image: Cage-lengths

5. Tooth Capacity

You must consider the required tooth capacity of your bike before purchasing a rear derailleur. This can be calculated using the following equation:

(largest cog – smallest cog) + (largest chainring – smallest chainring) = required capacity

For example, if the equation gives you a required capacity of 35 teeth, then you should buy a derailleur with a maximum capacity of at least 35. You can go with higher capacity derailleurs without a problem. However, going with a lower than required tooth capacity might limit your shifting in the extreme gear combinations.

6. Clutch Derailleurs

The majority of all modern mountain bike derailleurs have a clutch mechanism. A regular derailleur depends only on the return spring to keep tension in the chain. However, MTB riders often face rough terrain or jumps that cause the lower pivot of the derailleur to move around, causing chain slap or even the chain falling off. The clutch is basically a one-way friction damper that is built into the lower pivot to prevent it from swinging too easily. This practically eliminates the chance for the chain to fall off. There are no drawbacks to a clutch and you should definitely get a derailleur that includes one.

Derailleur clutch

Image: Derailleur-clutch

7. Price

Rear derailleurs can range in price from $20 to more than $200, with some electronic derailleurs costing upwards of $500. Now you might be thinking – what do I get in a derailleur for more money? Well, first of all, the overall quality and durability will improve with the price. The parts are better designed, harder wearing, and built with closer tolerances. Additionally, high-end derailleurs are lighter as they use more expensive materials, like carbon and titanium instead of steel. Finally, the looks and finish of a pricey derailleur will typically be better than those of a cheap one. So it’s up to you to decide where you want to spend a lot and which features you don’t mind skipping on.

Our Top Pick(s)

We thoroughly tested several popular mountain bike rear derailleurs. Then we narrowed the list down to 12 of the top products and reviewed them. Notice that all the products are by either SRAM or Shimano due to their dominance over the market. For the ‘Overall Best Choice’, this time we have selected two products – the Shimano RD-M8100/RD-M8120 and the SRAM GX Eagle Rear Derailleur – one for each brand.

Shimano RD-M8100/RD-M8120

Best choice for Shimano groupsets | Overall Best Choice

Both the Shimano RD-M8100/RD-M8120 and the SRAM GX Eagle Rear Derailleur are best-in-class derailleurs for a mountain bike. We have picked two options because mixing and matching between parts of different brands are not recommended. Also because we did not want to leave fans of either brand dissatisfied. They both stand out from the rest in terms of shifting performance, build quality and value for money among other things.

Shimano RD-M8100/RD-M8120 Specifications:

  • Gearing: 1×12-speed / 2×12-speed
  • Compatible Chain: HG+ 12 speed
  • Material: Aluminum, steel
  • Mount Type: Standard mount
  • Pulley Cage: Long (SGS)
  • Maximum Sprocket: 51 / 45 teeth
  • Minimum Sprocket: 10 teeth
  • Total Capacity: 41 / 45 teeth
  • Pulleys: 13 teeth
  • Weight: 284 / 290 grams

 

SRAM GX Eagle Rear Derailleur

Best choice for SRAM groupsets | Overall Best Choice

SRAM GX Eagle Rear Derailleur Specifications:

  • Gearing: 12-speed
  • Compatibility: Eagle GX, Eagle XO1, Eagle XX1
  • Material: Aluminum, steel
  • Pull Type: X-actuation
  • Mount Type: Standard mount
  • Pulley Cage: Long
  • Maximum Sprocket: 52 teeth
  • Total Capacity: 40 teeth
  • Pulleys: 12 teeth (g-pulley), 14 teeth (t-pulley)
  • Weight: 290 grams

 

A quick view of our list of the best bike derailleurs that we have selected for your mountain bikes:

DerailleurWeight (grams)Our Ratings
Shimano RD-M8100 / RD-M8120284 / 29093
SRAM GX Eagle29093
SRAM XX1 X-Horizon24591
SRAM Force 1265-26990
SRAM XX1 Eagle AXS37590
Shimano Ultegra RD-RX80024889
SRAM GX 1×11 X-Horizon26587
Shimano Deore RD-M600042685
Shimano ZEE RD-M640-SS27584
Shimano XT RD-M8000271 / 27582
Shimano Deore XT RD-M78626681
SRAM NX 1×11 X-Horizon32280

12 best mountain bike derailleurs you can buy today

DerailleurPreviewGearingMaterialMountCage SizeMaximum Sprocket
(teeth)
Total Capacity
(teeth)
Weight
(grams)
Shimano RD-M8100 / RD-M8120SHIMANO XT RD-M8100-SGS RD-M8120-SGS Rear Derailleur - 12-Speed, Long Cage, Black1×12-speed / 2×12-speedAluminium, steelStandard mountLong51 / 4541 / 45284 / 290
SRAM GX Eagle Rear DerailleurSRAM GX Eagle 12-Speed Rear Derailleur Black12-speedAluminium, steelStandard mountLong5240290
SRAM XX1 X-HorizonSRAM XX1 X-Horizon Rear Derailleur11-speedCarbon, ceramicStandard mountLong4232245
SRAM Force 1 Rear DerailleurSRAM Force 1 Type 3.0 Rear Derailleur Grey, Medium Cage10, 11-speedAluminium, steelStandard mountLong / medium / short28 / 36 / 4217 / 25 / 32265-269
SRAM XX1 Eagle AXS Rear DerailleurSRAM XX1 Eagle AXS Upgrade Kit - Rear Derailleur, Battery, Eagle AXS Controller w/Clamp, Charger/Cord12-speedCarbon, steelStandard mountLong5240375
Shimano Ultegra RD-RX800SHIMANO Ultegra RD-RX800 Rear Derailleur Gray, Long2×12-speedAluminium, compositeDirect mountMedium3439248
SRAM GX 1×11 X-HorizonSRAM GX 1x11 X-Horizon Rear Derailleur for 11 Speed - Long Cage, Black11-speedAluminium, steelStandard mountLong4232265
Shimano Deore RD-M6000SHIMANO Deore Mountain Bicycle Rear Derailleur - RD-M6000 (Black - GS)10-speedSteel, aluminiumStandard mount (direct mount compatible)Medium / long42 / 3641 / 43426
SHIMANO ZEE RD-M640SHIMANO RD-M640 Zee Shadow Plus 10 Speed Rear Derailleur10-speedAluminium, steelStandard mount (direct mount compatible)Short36 (freeride spec), 28 (DH spec)25275
Shimano XT RD-M8000SHIMANO XT RD-M8000 Rear Derailleur11-speedAluminium, steelStandard mount (direct mount compatible)Medium / long4639 / 47271 / 275
Shimano Deore XT RD-M786Shimano Deore XT RD-M786 SGS Shadow Plus Rear Derailleur, Black10-speedAluminium, steelDirect mountLong3643266
SRAM NX 1×11 X-HorizonSRAM NX 1X11 X-Horizon Rear Derailleur for 11 Speed - Long Cage, Black11-speedSteelStandard mountLong4225322

1. Shimano RD-M8100 / RD-M8120: Best choice for Shimano groupsets

Shimano RD-M8100 / RD-M8120
  • Gearing: 1×12-speed / 2×12-speed
  • Compatible Chain: HG+ 12 speed
  • Material: Aluminum, steel
  • Mount Type: Standard mount
  • Pulley Cage: Long (SGS)
  • Maximum Sprocket: 51 / 45 teeth
  • Minimum Sprocket: 10 teeth
  • Total Capacity: 41 / 45 teeth
  • Pulleys: 13 teeth
  • Weight: 284 / 290 grams

Features & Considerations
  • Fast and Smooth Shifting: The HYPERGLIDE+ technology features a cassette and chain design that improves the shifting of the chain by making it fast and shock less.
  • Double Front Chainring Option: There are two slightly different models to choose from. One is for a single chainring, while the other is for a double chainring.
  • Great Chain Tension: Shimano’s Shadow RD+ technology uses a stabilizer system to maintain high chain tension and reduce chain slap.
  • Silent Drivetrain: The derailleur ensures low noise during operation thanks to various design features. This will be less distracting for you while riding.
  • Compact Design: The unit has quite a low profile which makes it less prone to impacts and hence, less damage.
  • Wide Speed Range: This is built for a 12-speed drivetrain that offers more speed options for different terrain and difficulty levels.
  • Large Pulleys: The guide and tension pulleys have 13 teeth instead of the conventional 11 teeth. This reduces friction and wears in the derailleur.

Some Weaknesses
  • Clutch can get stuck sometimes but can be easily fixed.
  • Chain stabilizer will rust if even slight moisture gets in.

When purchasing this derailleur you have to choose from two versions. Both the RD-M8100 and the RD-M8120 are part of Shimano’s Deore XT M8100 series. The former is for a bike with a single front chainring, while the latter is compatible with double front chainrings. You get different gear combinations and slightly different specs with each version. However, that’s where the differences stop. In terms of performance and feel, they are almost identical.

These rear derailleurs are packed full of technologies that make it better than the rest of Shimano’s line-up. After testing we have verified that a bumper added to the cage, a chain stabilizer, large pulley wheels, and other features do fulfill their purpose as claimed. The improvements include high chain tension, low wear and noise, and most importantly, quick and seamless shifting. Additionally, not only do they have a sturdy build, but they also have a compact design that greatly decreases the chance of damaging impacts on the trail.

Shimano RD-M8100 / RD-M8120 Derailleur

Shimano RD-M8100 / RD-M8120 Derailleur

2. SRAM GX Eagle: Best choice for SRAM groupsets

SRAM GX Eagle Rear Derailleur
  • Gearing: 12-speed
  • Compatibility: Eagle GX, Eagle XO1, Eagle XX1
  • Material: Aluminum, steel
  • Pull Type: X-actuation
  • Mount Type: Standard mount
  • Pulley Cage: Long
  • Maximum Sprocket: 52 teeth
  • Total Capacity: 40 teeth
  • Pulleys: 12 teeth (g-pulley), 14 teeth (t-pulley)
  • Weight: 290 grams

Features & Considerations
  • Good Compatibility: This derailleur is compatible with multiple SRAM groupsets and cassette sizes, including 10-50t and 10-52t cassettes.
  • Sharp and Smooth Shifting: The shifting is fast and consistent across all gears in the cassette. It also has a smooth and precise feel to it.
  • Almost Zero Chain Slap: A clutch is included with a roller bearing which helps to eliminate chain slap and derailleur bounce.
  • Cage Lock Technology: With this, you can add slack to the chain so that installation and removal of the wheels and chain are much easier and faster.
  • Wide Speed Range: This derailleur is compatible with 12-speed drivetrains which give you more gear options for varying your cadence according to the terrain.
  • Large Pulleys: The guide and tension pulleys have 12 and 14 teeth respectively, instead of the conventional 11 teeth. This reduces friction and wears in the derailleur.
  • Excellent Durability: This derailleur is quite durable and it also has mud-clearing recesses to keep it clean and wear-free.

Some Weaknesses
  • A bit on the heavier side, considering the price.

The SRAM GX Eagle Rear Derailleur is part of SRAM’s popular GX Eagle groupset. The installation is surprisingly easy. It should take about an hour if you include installation of the XD driver. As in all SRAM mechs, the cable management is great. You can also use this mech with Eagle XX1 and Eagle XO1 components without a problem. Moreover, you have flexibility with the cassette size as well. This derailleur has the best combination of overall quality and price among all of SRAM’s rear derailleurs.

The performance you get while riding is simply incredible. The shifting is probably one of the smoothest that we have experienced. There is also no bounce or chain slap even during intense jumps and drops. This is made possible by many technologies that are usually found only in the most premium derailleurs. Other than that, we found the cage lock to be the most convenient feature of this unit. You can push it forward and lock it in place to add extra chain slack. This makes the removal of wheels and the chain a very simple process.

SRAM GX Eagle Rear Derailleur

SRAM GX Eagle Rear Derailleur

3. SRAM XX1 X-Horizon: Lightweight derailleur w/ carbon & ceramic parts

SRAM XX1 X-Horizon
  • Gearing: 11-speed
  • Compatibility: SRAM XX1
  • Material: Carbon, ceramic
  • Pull Type: X-actuation
  • Mount Type: Standard mount
  • Pulley Cage: Long
  • Maximum Sprocket: 42 teeth
  • Total Capacity: 32 teeth
  • Pulleys: 12 teeth
  • Weight: 245 grams

Features & Considerations
  • Lightweight: The carbon cage and ceramic bearings take off weight from the unit without compromising on durability.
  • Sharp and Smooth Shifting: Shifting from one gear to another is smooth, precise, and consistent throughout all the cogs of the cassette.
  • Negligible Chain Slap: The roller bearing clutch technology works to keep chain slap and derailleur bounce to a minimum.
  • Cage Lock Technology: You can fix the position of the cage to loosen the chain which makes the replacement of wheels much easier.
  • Wide Speed Range: This is built for an 11-speed drivetrain that offers more speed options for different terrain and difficulty levels.
  • Excellent Durability: This derailleur will last for a long time due to its ruggedness and its ability to clear away mud on its own.

Some Weaknesses
  • The price is a little high.
  • The return spring needs to be improved.

The SRAM XX1 X-Horizon is an excellent rear derailleur for mountain biking, especially if you want to make your bike as light as possible. At 245 grams, this is one of the lightest mechs that are available in the market. However, it does not lack durability thanks to the ceramic and carbon parts. We tested it with multiple hard impacts and it survived with only scratches to the surface. There are also technologies such as X-actuation, X-sync, roller bearing clutch, and others that enable it to perform optimally in all conditions.

The shifting is smooth and crisp when it does work. But on a couple of occasions, there was an issue with the spring which caused the shift to just not occur. This probably will not be much of an issue since we tested the derailleur for weeks and it only happened two times and is easily fixed. Other than that, there are no problems such as chain slap, ghost shifting, etc. This model also has the cage lock features which allows you to change the chain or wheels with ease. The price is a bit high, but you’ll get your money’s worth.

SRAM XX1 X-Horizon Derailleur

SRAM XX1 X-Horizon Derailleur

4. SRAM Force 1: Versatile derailleur for both MTB & road drivetrains

Sale
SRAM Force 1 Rear Derailleur
  • Gearing: 10, 11-speed
  • Compatibility: SRAM MTB, SRAM Road
  • Material: Aluminum, steel
  • Pull Type: Exact actuation
  • Mount Type: Standard mount
  • Pulley Cage: Long / medium / short
  • Maximum Sprocket: 28 / 36 / 42 teeth
  • Total Capacity: 17 / 25 / 32 teeth
  • Pulleys: 12 teeth
  • Weight: 265-269 grams

Features & Considerations
  • Sharp and Smooth Shifting: You get consistently accurate and seamless shifting performance across the entire cassette.
  • Almost Zero Chain Slap: To minimize the possibility of the chain falling off, a roller bearing clutch has been included that keeps up tension in the chain.
  • Cage Lock Technology: This allows you to lock the cage in a forward position and add slack to the chain. Then you can easily remove the chain or wheels.
  • Exact Actuation: This implies a 1:1 actuation ratio between the cable and derailleur which simplifies the setup of the index shifting system.
  • Cage Length Options: You have the option to choose the cage size – long, medium, or short – that best fits your requirements.
  • Versatile: This derailleur is compatible with SRAM MTB and Road drivetrains making it usable for riders of various disciplines.

Some Weaknesses
  • You could accidentally shift in the opposite direction by double-tapping.
  • The cost could be lower.

The SRAM Force 1 Rear Derailleur is uniquely capable of catering to your needs. First of all, you can choose the cage length while purchasing. All three options – long, medium, and short – are available. Secondly, this derailleur is compatible with both SRAM road and MTB drivetrains, making it a highly versatile mech that can be used by all riders. Installing it was not too complicated and you can do it yourself. Moreover, the 1:1 cable pull ratio makes the setup of the index shifting a simple process.

When it comes to shifting, it is spot-on nearly every time. It feels smooth and snappy, boosting your confidence on difficult terrain. It was also able to handle going through rough jumps pretty well. The roller bearing clutch virtually eliminates chain slap and derailleur bounce. To facilitate easy replacement of wheels and the chain, you can lock the cage in place so that there is extra slack in the chain. All in all, this is a great rear derailleur for multi-purpose use.

SRAM Force 1 Rear Derailleur

SRAM Force 1 Rear Derailleur

5. SRAM XX1 Eagle AXS: Electronic actuation for the highest level of performance

SRAM XX1 Eagle AXS Rear Derailleur
  • Gearing: 12-speed
  • Compatibility: Eagle XX1 AXS, Eagle XO1 AXS
  • Material: Carbon, steel
  • Pull Type: Electronic actuation
  • Mount Type: Standard mount
  • Pulley Cage: Long
  • Maximum Sprocket: 52 teeth
  • Total Capacity: 40 teeth
  • Pulleys: 12 teeth (g-pulley), 14 teeth (t-pulley)
  • Weight: 375 grams

Features & Considerations
  • Electronic Shifting: A small motor replaces the cable which makes the shifting much smoother and precise compared to other mechs.
  • AXS App: This app allows you to check the remaining battery, customize the controls, and even get maintenance updates.
  • Overload Clutch: During an impact, the motor gearbox is disengaged and the derailleur body can move. It then immediately returns to its position.
  • Cage Lock Technology: To make it convenient for you to replace the chain or wheels, you can fix the cage in a forward position to loosen the chain.
  • Wide Speed Range: It works with 12-speed drivetrains that have more speed options and let you navigate all kinds of terrain.
  • Large Pulleys: The guide and tension pulleys are larger and have more teeth than pulleys, which reduces friction and wear in the derailleur.
  • Excellent Durability: This derailleur can withstand a large number of heavy impacts and also automatically clear dirt and grit for minimal wear.

Some Weaknesses
  • Getting the entire kit is very expensive.
  • It is significantly heavier than most mechanical derailleurs.

The SRAM XX1 Eagle AXS Rear Derailleur is an electronically controlled mech. Just by incorporating this motor-driven system, it has significant advantages over cable-actuated derailleurs. Firstly, the shifting is perfectly smooth and accurate. Issues such as ghost shifting and failure to shift are eliminated. Second of all, you don’t have to deal with managing the cable since there is none. And finally, shifting gears is done with the push of a button which requires much less force from your hand.

Another unique feature about this derailleur is that there is not one, but two clutches. One is to ensure chain tension and reduce bouncing. The other one is called an overload clutch. This allows the derailleur body to move during an impact and then immediately return to its position. This freedom for movement significantly reduces damage and prolongs life. The mech is powered by a detachable battery which lasts for around 20-25 hours of ride time. The entire system is also water and dustproof.

SRAM XX1 Eagle AXS Rear Derailleur

SRAM XX1 Eagle AXS Rear Derailleur

6. Shimano Ultegra RD-RX800: Lightweight derailleur for 2× drivetrains w/ direct mount

Shimano Ultegra RD-RX800
  • Gearing: 2×12-speed
  • Compatible Chain: HG-EV 11-speed / HG-X 11-speed
  • Material: Aluminum, composite
  • Mount Type: Direct mount
  • Pulley Cage: Medium (GS)
  • Maximum Sprocket: 34 teeth
  • Minimum Sprocket: 11 teeth
  • Total Capacity: 39 teeth
  • Pulleys: 11 teeth
  • Weight: 248 grams

Features & Considerations
  • Lightweight: The derailleur has aluminum and composite parts which helps to bring the weight down to just under 250 grams.
  • Double Front Chainring Option: This rear derailleur is compatible with a double front chainring allowing you to use a front derailleur as well.
  • Great Chain Tension: The Shadow RD+ technology by Shimano features a chain stabilizer that pulls on the chain to add extra tension and prevent chain slap.
  • Direct Mount: In contrast to a conventional mount, the direct mount’s design allows easier removal and installation of the rear wheel.
  • Versatile: You can use this derailleur with both MTB and road drivetrains by Shimano. It is also compatible with dual control levers.
  • Wide Speed Range: Since this is built for a 12-speed cassette, you get more gear options to make the pedaling as easy or as difficult as you want.

Some Weaknesses
  • Shifting is better when the clutch is off.
  • Initially felt like there was a bit too much friction, but got better over time.

The Shimano Ultegra RD-RX800 is part of the Ultegra RX800 series. It works best for less aggressive trail riding, as well as gravel and cyclocross. Since it is compatible with both Shimano MTB and road groupsets, riders of all disciplines can use it. Even though this does not use a standard mount, the installation process is basically the same. It can also be fitted onto just about any frame. The difference is in the design, which leaves more space for easy removal and installation of the rear wheel.

The derailleur incorporates Shimano’s Shadow RD+ technology which features a clutch or as they call it, a chain stabilizer. This can be turned on/off. When on, there is almost no chain slap or bounce from the mech body. However, to us, the shifting felt slightly better when the clutch was off. Either way, it’s up to you to decide which setting you prefer. Another great feature is that you can use this mech with front double chainrings if your bike has them. Overall we would say, this is an excellent derailleur for all kinds of cyclists.

Shimano Ultegra RD-RX800 Derailleur

Shimano Ultegra RD-RX800 Derailleur

7. SRAM GX 1×11 X-Horizon: Affordable derailleur for SRAM 1×11 MTB drivetrains

SRAM GX 1×11 X-Horizon
  • Gearing: 11-speed
  • Compatibility: SRAM MTB
  • Material: Aluminum, steel
  • Pull Type: X-actuation
  • Mount Type: Standard mount
  • Pulley Cage: Long
  • Maximum Sprocket: 42 teeth
  • Total Capacity: 32 teeth
  • Pulleys: 12 teeth
  • Weight: 265 grams

Features & Considerations
  • Affordable: At less than a $100, this derailleur is less expensive compared to other equally good products.
  • Negligible Chain Slap: Chain slap is the primary reason for the chain falling off. A built-in roller bearing clutch gets rid of this problem.
  • Cage Lock Technology: With this, you can add slack to the chain so that installation and removal of the wheels and chain are much easier and faster.
  • Wide Speed Range: This is built for an 11-speed drivetrain that offers more speed options for different terrain and difficulty levels.
  • Excellent Durability: This derailleur is pretty durable and it features mud-clearing recesses to keep it clean and free of wear.

Some Weaknesses
  • Shifting is good but not as smooth as higher-end mechs.

The SRAM GX 1×11 X-Horizon is a great rear derailleur at a lower mid-range price. It works seamlessly with the GX groupset and is also compatible with other SRAM MTB groupsets. However, you can only use 1×11 drivetrains, as the name suggests. The mounting process is the same as with any SRAM rear derailleur. The shifting performance is very good. It is not as crisp as the SRAM mechs mentioned above, but there’s a marginal difference that most people probably won’t even notice.

In terms of other features, it seems to be on par with the high-end SRAM products. It has all the same technologies built-in, such as X-sync, X-horizon, roller bearing clutch, and even the cage lock. The unit is sturdily constructed with aluminum and steel parts. It took a lot of hits during our testing, and it made it to the end with only some scratches. We can’t say for sure about its long term durability, but it’s definitely not flimsy. To sum it up, this is a decently high performing mountain bike derailleur at a more palatable price.

SRAM GX 1×11 X-Horizon Derailleur

SRAM GX 1×11 X-Horizon Derailleur

8. Shimano Deore RD-M6000: Medium & long cage options, direct mount compatible

Sale
Shimano Deore RD-M6000
  • Gearing: 10-speed
  • Compatible Chain: HG-X 10-speed
  • Material: Steel, aluminum
  • Mount Type: Standard mount (direct mount compatible)
  • Pulley Cage: Medium (GS) / long (SGS)
  • Maximum Sprocket: 42 / 36 teeth
  • Minimum Sprocket: 11 teeth
  • Total Capacity: 41 / 43 teeth
  • Pulleys: 11 teeth
  • Weight: 426 grams

Features & Considerations
  • Fast and Smooth Shifting: The DYNA-SYS technology found in Shimano’s 10-speed drivetrains allows for seamless and efficient gear shifting.
  • Affordable: This is one of the least expensive rear derailleurs that is also good enough to be used by professional mountain bikers.
  • Great Chain Tension: The patented Shadow RD+ technology utilizes a clutch that can be turned on/off to apply enough tension on the chain and prevent any bouncing.
  • Silent Drivetrain: Various design features ensure that the noise levels are kept at a level that will not be distracting for you.
  • Cage Length Options: You can select the long cage option if you have a triple front chainring or a medium length cage for a double front chainring.
  • Direct Mount Compatible: This derailleur can be installed to your bike frame using either a standard mount or a direct mount.

Some Weaknesses
  • It is significantly heavier than the other products on this list.

The Shimano Deore RD-M6000 comes in two versions – one with a long cage (SGS) and the other with a medium cage (GS). You can use the GS version for a 2× drivetrain and the SGS version for a 3× drivetrain. Of course, it is compatible with a regular 1× drivetrain as well. Additionally, this derailleur is compatible with both a standard mount and a direct mount. Using a direct mount makes it easier to remove the rear wheel when needed.

The RD-M6000 was built for 10 rear speeds and it performs superbly for mountain biking applications. The shifting is responsive, it runs with low noise and there is good consistent tension in the chain which is enabled by the chain stabilizer. As a bonus, if you use this derailleur with the M6000 series products then the shifting requires a noticeably lower effort at the lever. Basically, with this rear mech, you get excellent mountain biking performance at a comparatively lower price.

Shimano Deore RD-M6000 Derailleur

Shimano Deore RD-M6000 Derailleur

9. Shimano ZEE RD-M640-SS: Best budget option for Shimano

Shimano ZEE RD-M640-SS
  • Gearing: 10-speed
  • Compatible Chain: HG-X 10-speed
  • Material: Aluminum, steel
  • Mount Type: Standard mount (direct-mount compatible)
  • Pulley Cage: Short (SS)
  • Maximum Sprocket: 36 teeth(freeride spec), 28 teeth (DH spec)
  • Minimum Sprocket: 11 teeth
  • Total Capacity: 25 teeth
  • Pulleys: 11 teeth
  • Weight: 275 grams

Features & Considerations
  • Fast and Smooth Shifting: The DYNA-SYS technology found in Shimano’s 10-speed drivetrains allows for seamless and efficient gear shifting.
  • Affordable: This is the most affordable derailleur that we have included, making it the best choice for cycling enthusiasts on a tight budget.
  • Great Chain Tension: A clutch or chain stabilizer adds tension to the chain so that there is no derailleur bounce or chain slap. This technology is called Shadow RD+.
  • Silent Drivetrain: You will not get annoyed by any excessive noise because multiple design features are available to reduce sounds from the mech.
  • Two Specs Available: There is an option that is better for freerides, while the other spec is suitable for downhill riding.
  • Direct Mount Compatible: This derailleur can be installed to your bike frame using either a standard mount or a direct mount.

Some Weaknesses
  • Not as durable as other models for downhill riding.

The Shimano ZEE RD-M640-SS is advertised as a gravity MTB derailleur. We were initially drawn to it because of the remarkably low price. In fact, this is the cheapest Shimano derailleur that we have reviewed here. Before buying, you have to choose which spec to get. There are two options, one of which is for freerides and the other is for downhill riding. The freeride spec has a maximum sprocket size of 36 teeth, while the downhill spec has a maximum sprocket size of 28 teeth.

Let’s start with the bad. Near the end of our weeks-long testing, the derailleur began to show signs of damage. We did put it through the wringer, but it may not last in the long run for regular downhill rides. This is most likely a result of the low cost. Other than that, everything else is top-notch. It did not make too much noise, the clutch maintained good tension in the chain and shifting was smooth and precise. Moreover, it works with a standard mount as well as a direct mount.

Shimano ZEE RD-M640-SS Derailleur

Shimano ZEE RD-M640-SS Derailleur

10. Shimano XT RD-M8000: Cage length options, direct mount compatible

Shimano XT RD-M8000
  • Gearing: 11-speed
  • Compatible Chain: HG-X 11-speed
  • Material: Aluminum, steel
  • Mount Type: Standard mount (direct mount compatible)
  • Pulley Cage: Medium (GS) / long (SGS)
  • Maximum Sprocket: 46 teeth
  • Minimum Sprocket: 11 teeth
  • Total Capacity: 39 / 47 teeth
  • Pulleys: 11 teeth
  • Weight: 271 / 275 grams

Features & Considerations
  • Fast and Smooth Shifting: The DYNA-SYS11 technology for Shimano’s 11-speed drivetrains allows for seamless and efficient gear shifting.
  • Great Chain Tension: Extra tension is added to the chain by a stabilizer/clutch which is part of the Shadow RD+ technology.
  • Silent Drivetrain: Multiple features in the derailleur work to keep the sound generated during riding at a low level.
  • Cage Length Options: You will be able to choose a long cage option if you have a triple front chainring or a medium length cage for a double front chainring.
  • Direct Mount Compatible: This derailleur can be installed to your bike frame using either a standard mount or a direct mount.

Some Weaknesses
  • The durability of the clutch is not great.

The Shimano XT RD-M8000 is another Shimano rear derailleur that is available in two different cage lengths – long and medium. This derailleur is the predecessor of the RD-M8100. You could say that this is sort of in the middle of the Shimano line-up. You get gear shifting performance that is comparable to the best of Shimano, while also having a price that’s within the reach of all people. In other words, this mech offers the best value for money among the Shimano products in our opinion.

Installation is pretty straightforward if you have some experience. You could go with either a direct mount or a conventional mount. It is compatible with 1×, 2×, and 3× drivetrains. Just be sure to get the long cage (SGS) version if you’re planning to use it with triple front chainrings. The unit held up very well on bumpy rides, the chain stabilizer or clutch maintaining ample tension throughout. However, the clutch does feel a bit cheap and it probably won’t last you years. Other than that, this is an overall great product.

Shimano XT RD-M8000 Derailleur

Shimano XT RD-M8000 Derailleur

11. Shimano Deore XT RD-M786: Compatible with 1×, 2×, or 3× drivetrains

Shimano Deore XT RD-M786
  • Gearing: 10-speed
  • Compatible Chain: HG-X 10-speed
  • Material: Aluminum, steel
  • Mount Type: Direct mount
  • Pulley Cage: Long (GS)
  • Maximum Sprocket: 36 teeth
  • Minimum Sprocket: 11 teeth
  • Total Capacity: 43 teeth
  • Pulleys: 11 teeth
  • Weight: 266 grams

Features & Considerations
  • Fast and Smooth Shifting: The DYNA-SYS technology found in Shimano’s 10-speed drivetrains allows for seamless and efficient gear shifting.
  • Great Chain Tension: The Shadow RD+ technology by Shimano features a chain stabilizer that pulls on the chain to add extra tension and prevent chain slap.
  • Silent Drivetrain: The derailleur generates less noise while riding thanks to certain design features, which will be less distracting for you.
  • Direct Mount: This derailleur is installed to your bike frame using a direct mount which leaves more space to remove/mount the rear wheel easily.
  • Multiple Chainring Compatible: You can use this derailleur with a 1×, 2×, or even a 3× drivetrain for a wide range of gears.

Some Weaknesses
  • It is a bit pricey compared to other Shimano derailleurs.

The Shimano Deore XT RD-M786 is a versatile 10-speed derailleur that is compatible with single, double, and even triple front chainrings. Just like most of Shimano’s latest rear derailleurs, this one also has Shadow RD+. This technology features a clutch, also called a chain stabilizer, to keep a high level of tension in the chain and prevent any bouncing or chain slap. The best part about this is that you can turn it on/off as you wish. The mech also contains other features such as DYNA-SYS that improve the performance.

The shifting feels quite smooth and precise, and it behaves consistently throughout all the cogs. There isn’t any excessive noise produced either, so you won’t get annoyed. Instead of using a hanger, the body of this mech mounts directly to the frame. This direct-mount is larger and offers more room for easy replacement of the rear wheel when needed. It is also pretty durable and can take a beating. You can use the RD-M786 for all subdisciplines of mountain biking.

Shimano Deore XT RD-M786 Derailleur

Shimano Deore XT RD-M786 Derailleur

12. SRAM NX 1×11 X-Horizon: Best budget option for SRAM

Sale
SRAM NX 1×11 X-Horizon
  • Gearing: 11-speed
  • Compatibility: All SRAM MTB 1× drivetrains
  • Material: Steel
  • Pull Type: X-actuation
  • Mount Type: Standard mount
  • Pulley Cage: Long
  • Maximum Sprocket: 42 teeth
  • Total Capacity: 25 teeth
  • Pulleys: 12 teeth
  • Weight: 322 grams

Features & Considerations
  • Affordable: This is the least expensive SRAM rear derailleur that is available in the market for SRAM MTB drivetrains.
  • Almost Zero Chain Slap: A clutch with a roller bearing has been incorporated to help get rid of chain slap and derailleur bounce.
  • Cage Lock Technology: Chain slack can be added intentionally by locking the cage in place. This makes it easier to remove/install the wheels or the chain.
  • Wide Speed Range: This is built for an 11-speed drivetrain that offers more speed options for different terrain and difficulty levels.
  • Excellent Durability: This is a long-lasting derailleur since it can take a lot of beating and can keep itself clean using built-in recesses.

Some Weaknesses
  • It is heavier than most other derailleurs.
  • Not sturdy enough for aggressive mountain biking.

The SRAM NX 1×11 X-Horizon offers the best value for money among all the SRAM derailleurs that we have listed. It has to be installed using a standard mount and the process itself should take less than an hour. Since this derailleur is so cheap, we tried it out on older bikes to see if that demographic can use this. Turns out you can, but you’ll need a spacer in between the derailleur and the hanger. This is because older hubs are smaller than modern hubs. When it comes to drivetrain compatibility, this one is built for 1×11 speeds.

Performance-wise, the shifting is both smooth and accurate. It is also extremely reliable as we haven’t had any failures or ghost shifting so far. The build quality is decent but we don’t think that some of the parts can withstand frequent heavy impacts. The entire body is made of steel only. This makes it weigh a few dozen grams more than the average weight of similar mechs. This is also one of the reasons why it costs so less. If you are looking to save money, then this is the one.

SRAM NX 1×11 X-Horizon Derailleur

SRAM NX 1×11 X-Horizon Derailleur


Frequently Asked Questions

Q1. Can I use a MTB derailleur on a road bike?

Ans.: The answer depends primarily on what brand of groupset you are using and the gear range available. In some cases, you can and in others, you can’t. The reverse is also possible. We have discussed derailleur compatibility in detail in the buying guide section above. You can check that out to know more.

Q2. Is SRAM as good as Shimano?

Ans.: Both Shimano and SRAM make high-quality cycling products. Hence, why they dominate the market. It is really hard to tell for sure which is better. While Shimano has been around for a lot longer, SRAM is the one that has been leading in innovation in the last decade. Each company includes its own unique features in the products. For example, Shimano derailleurs have a clutch that can be turned on and off, while you can lock the cages of SRAM derailleurs in place for convenience while removing a wheel. We have gone back and forth between the two many times now, but in the end, we love both companies’ products.

Q3. Benefits of derailleurs with a clutch mechanism?

Ans.: The clutch mechanism present in most mountain bike derailleurs today is a simple but useful feature to have. It helps to maintain tension in the chain during intense jumps and on bumpy trails. The result is that the bouncing of the derailleur is eliminated and hence, the chain will not fall off so easily. Another outcome is that noise and wears in the drivetrain are reduced.

Q4. How do I fix the shifting in my rear derailleur?

Ans.: A rear derailleur needs to be adjusted from time to time for optimum performance. The different parts can get out of alignment due to impacts or other reasons. This may cause shift failures or excessive noise. The following video provides a comprehensive guide to adjusting your rear derailleur.

How to Adjust a Rear Derailleur – Limit Screws & Indexing

Conclusion

Reading through this article should give you a near-complete understanding of how bike derailleurs work and what criteria your decision to buy should be based upon. Other brands make bike derailleurs, but our top picks came down to SRAM and Shimano. Whether you are a fan of one or the other, we guarantee that all the products listed above will serve you well. Hopefully, this article helped you out. Thank you!

My name is Dion Lewis. I’ve been cycling since my childhood. When I was in high school, I started racing in our local competitions. In my college life, I took a part-time job in a bicycle shop and I learned how to repair and maintain bicycles professionally. Though I love racing, mountain biking is another thing I do frequently. My friends, neighbors, and colleagues treat me as an avid rider and take my suggestions while they plan for a new bike or bike gear.

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