How To: Installing A Rear Derailleur (Install Like a Pro!) [Video]

Words by: Max Morgan

Being out on the trail with your derailleur not shifting through the gears properly can be an aggravating thing. After reading this MTB How To, you should be an expert on how to install and set up your rear derailleur. Here we are going to be installing a Shimano XT M8000 rear derailleur for a 1x11 drivetrain. Installing a derailleur from Sram or Box Components follows a very similar method.

What Tools Do We Need?

To get the job done right, we are going to need the right set of tools. To install and set up a new rear derailleur, we are going to need a set of allen keys, a phillips screw driver, cable cutters, chain break tool or chain pliers, and a pair of pliers. To get a closer look at what's inside a pro tool box, check out our Pro Tool Box Check. 

1. Remove Chain and Old Derailleur

• Before we get started with the new derailleur, remove the old one and get it out of the way. 
• Remove the chain as well. Even though this is a Shimano chain, it is using a 11 speed Sram Powerlock link for quick removal and install. Using the chain quick link pliers, remove the chain. 
• This is a good time to replace the shifter cable and housing. So remove that as well. 

2. Mount New Derailleur 

• Before installing the new derailleur, make sure the current derailleur hanger is in good shape. Make sure that the hanger is visibly straight, has no stress marks or nicks, and that the threads are not damaged. If the derailleur hanger is damaged, the new derailleur will never shift like it should.
• Double check that the new derailleur has some kind of thread locker on the threads. This will keep the threads from backing out and the derailleur coming loose from all the vibrations when riding. 
• Using a 5mm allen key, mount the Shimano XT derailleur. Make sure you don't over tighten.

3. Install Chain 

• If you are installing a brand new chain, see our MTB How To: Installing A New Chain to make sure you set the correct chain length. 
• When installing a Shimano chain, make sure the engraving on the chain links face outward. Shimano chains are directional. 

4. Set High Limit Screw

• Now we need to adjust the high and low limit screws. These are here to limit the derailleur's maximum movement in either direction so that the chain does not get thrown off the cassette. 
• Start with the high limit screw. You will see an H embossed next to the correct limit screw. The high limit screw limits the derailleur when in its highest gear (smallest cog). 
• Turn the limit screw clockwise with a 2mm allen key to move the derailleur towards the bigger cogs and vice versa. Line up the idler pulley on the derailleur with the highest gear. 
• At this point, there is no cable tension on the derailleur as the cable and housing has not been attached. While pedaling the bike in a bike stand, push the derailleur in toward to the larger gears to shift the derailleur manually. Make sure that when released while continuously pedaling, the chain drops back in to the highest gear with ease. 

5. Set Low Limit Screw

• Repeat the same process described above to set the low limit screw. Use a 2mm allen key to adjust the limit screw.
• You will have to pedal the bike in the stand and push the derailleur manually into the lowest gear. Make sure that the derailleur allows the chain to find its way into first gear with ease. 
• Turn the low limit screw clockwise to move the derailleur towards the smaller cogs and vice versa. Line up the upper idler pulley on the derailleur with the lowest gear (biggest cog).
• Remember setting the limit screws does not affect how the derailleur indexes through the gears, only limits the derailleurs travel in either direction. 

6. Install Cable Housing and Cable

• Now it's time to install the cable housing and shifter cable.
• Measure the correct length cable housing and cut it to length using your cable cutters. After the cut is made, make sure the ends of the housing are not crimped.
• Around the base of the shift levers on the shifter, remove the plastic phillips head screw with a screwdriver and push the new cable through the shifter. Reinstall the plastic phillips head screw. 
• Feed the cable through the housing and attach the appropriate ferrels to the ends of the cable housing. 
• Run the cable through the derailleur, make sure the shifter is in its hardest gear, pull the shifter cable tight by hand, and clamp the cable down using a 4mm allen key. 
• Using the cable cutters, cut the cable giving yourself 1-2 inches of excess cable past the cable clamp. Crimp the end of the shifter cable to prevent it from splitting. 

7. Adjust Cable Tension 

• Now it is time to make some final adjustments so the chain is indexing through each gear perfectly. 
• Use the barrel adjuster at the shifter to adjust the cable tension. Turning the barrel adjust out increases the cable tension and makes it easier for the chain to index up into an easier gear. 
• Turning the barrel adjuster in decreases the cable tension and makes it easier for the chain to index down into a harder gear. 
• While pedaling the bike in a stand, start in the highest gear (smallest cog) and shift the derailleur up one gear at a time. If the chain hesitates to up shift into a bigger cog, increase the cable tension. 
• Fine tune the cable tension so the derailleur is shifter up and down flawlessly. 

This article was written / authored by Max Morgan. Max has been a professional downhill mountain bike racer for the last 10 years, competing in the UCI World Cup downhill series and U.S. Pro GRT series. Having ridden all different kinds of bikes on trails all over the world, Max's experiences being out on the circuit give him a unique perspective on what makes for a quality cycling component. Max also has degrees in Mechanical Engineering and Physics, and so if you don't see out on the trail, chances are he is probably in the garage tinkering on the next project.