How to Install A Rear Derailleur on A Mountain Bike?

If you are a mountain bike lover, then this article will help you to know how to install a rear derailleur on a mountain bike? Read on to know about this process that can potentially enhance your overall biking experience.

For those who aren’t aware – a derailleur is a toggle-operated device that enables riders to shift their mountain bike chains from one sprocket (also called chain wheels or chainrings) to another.

It helps them control their input, measured in pedaling effort, to produce maximum output, measured in terms of speed gained or distance covered.

So, if you’ve recently found your love for mountain biking and don’t really know much about how rear derailleur’s work, there’s at least one thing you should know.

Although rear derailleurs are tough, over time, the action of your bike chain shifting from one sprocket to another will deteriorate the metal surface of the rear derailleur pulleys, making them more pointed and triggering a decline in performance.

This will eventually necessitate you to remove the rear derailleur and install it again with newer fittings. Plus, just like any other moving bike part, the rear derailleur too will benefit from regular maintenance and frequent cleanings.

Although removing and installing a rear derailleur isn’t really a simple process, you can easily perform it at home with the right guidance.

So, you can now either take the bike to a workshop for this task and spend hard-earned dollars on it, or read this guide and save yourself a plethora of dollars.

If you look up “how to install a rear derailleur on a mountain bike,” you’ll probably be flooded with a myriad of different methods and recommendations, making you feel overwhelmed; but fret not. We’ve got your back.

In this guide, we’ll help you first understand how a rear derailleur works and will share a super simple technique to remove and re-install it from the comfort of your home.

So, without any more delays, let us get started!

Table of Contents show

Understanding Rear Derailleurs for Enhanced Biking Experience

A mountain bike might have either a front and rear derailleur, or a rear derailleur only. Considering that the chain has a fixed length, it can’t stay in tension on all sprockets due to their different sizes.

Therefore, a derailleur not only ensures the bike chain shifts to different sprockets, but it also takes up and discharges slack as necessary to make sure the chain remains taut at all times.

Mountain bikes that have more than one sprocket on the rear gear set, the rear derailleur plays a critical role. It smooths shifting between these sprockets, enabling riders to swiftly spin uphill and exert some power on the flats.

Unlike the front derailleur, which only has one job to do – i.e. shifting between chainrings – the rear derailleur has another task to accomplish that’s just as important: taking up slack in the chain as the size of currently utilized gear differs.

The rear derailleur is fixed at the bottom end of the rear sprockets and comprises a moveable, spring-loaded arm with two pulleys that direct your bike chain in an S-shape.

The bike chain is guided over the head of the rear cassette (set of sprockets), looping around the rear where it meets the upper pulley of the rear derailleur.

This first pulley performs the key role of switching amid rear cogs and also deflects the chain back towards the second rear derailleur pulley.

This pulley spreads downwards on the derailleur’s spring-loaded arm and sustains pressure in the chain to ensure the bike works efficiently in an array of gears.

As we said earlier, like most moving bike parts, the rear derailleur also benefits from regular maintenance.

Whether you’re performing maintenance, purchasing a new rear derailleur, or simply want to know how this crucial component is installed, this post will walk you through the basics.

Also read, How to ride mountain bike on snow

How to Install A Rear Derailleur on A Mountain Bike?

Installing a rear derailleur on a mountain bike at home requires great precision and time.

As you are reading this post, we take the liberty to assume that this is your first installing a rear derailleur on a mountain bike, and we only have one thing to say to you: DON’T PANIC!

Even if you’ve never done this before, there is nothing to worry about. Below we’ve outlined some super simple steps that you can follow to accomplish the task.

Plus, to get your mountain bike rear derailleur perfectly installed all you really need is a Hex/Allen key, some screwdrivers, a bike stand, and five to ten minutes of your time.

Before You Begin

Moving on with the assumption that this is your first-ever rear derailleur installation crackdown, you most likely won’t have the appropriate tools required for the job.

Therefore, before you get started, make sure you have all the right supplies for the job. After all, you wouldn’t want to end up with a damaged rear derailleur, would you?

Installing Rear Derailleur In 6Simple Steps

Estimate time:10to 15 minutes

Basic Tools & Things You’ll Need

Allen key set
Cable cutter
Screwdriver
Pair of pliers
Chain pliers/ chain break tool
Bike stand

Step #1 Remove Old Derailleur and Chain

Before you get started with the new rear derailleur, you must first remove the old one and get it out of the way.
Next, with the help of chain quick link pliers, detach the bike chain as well.
This is an equally good time to swap the shifter cable and housing, so try removing them too.

Step #2 Mount New Rear Derailleur

Before you install the new rear derailleur, it is crucial to ensure that the existing rear derailleur hanger is in decent shape. An ideal rear derailleur hanger should be visibly straight, have no damaged threads as well as no nicks or stress marks. It’s important to note that the new rear derailleur would never shift like it ought to if the rear derailleur hanger is impaired in any way. Hence, be careful!
Once you’re confident about the hanger’s condition, move to ensure that the new rear derailleur has some type of thread locker present on the threads. This prevents the rear derailleur from getting loose from all the tremors (when riding) and keeps the threads from backing out.
Next, using a 5mm Allen key, hoist the new rear derailleur on the hanger of your mountain bike. Ensure to not tighten it excessively.

Step #3 Reattach Bike Chain

If you’re installing a brand-new chain or don’t really know how to do it, be sure to check our guide on “How to Install A Bike Chain on A Mountain Bike”. This post will help you set the correct chain length and will also provide you step-by-step instructions on how to best accomplish the task.
Place your new chain into the biggest chain ring and largest cog. Case the chain to each end, but ensure you don’t go through the derailleur.
Next, add two links and detach the remaining links with a chain cutter.
Strand the chain into the derailleur properly and lock it in position using a missing link.

Read How to Adjust Front Shocks on a Mountain Bike?

Step #4 Adjust Limit Screws

In this step, you’ll have to adjust the high and low limit screws. These screws constraint the rear ’derailleur’s maximum movement in either direction to ensure the chain doesn’t get thrown off the cassette.

Fix High Limit Screw

You should always begin with setting the high limit screw. Doing this limits the derailleur when it reaches the highest gear (smallest cog). There’s usually an ‘H’ engraved next to the correct limit screw.
Rotate the limit screw towards your right with an Allen key to move the rear derailleur towards the larger cogs and vice versa.
Next, line up the idle derailleur pulley with the highest gear.
At this point, there should be no cable pressure on the rear derailleur as both the housing and cable haven’t been attached. While pedaling your mountain bike on a bike stand, push the rear derailleur in towardsthe larger gears in order to manually shift the derailleur. Ensure that when you stop pedaling, the chain should easily drop back into the highest gear.

Fix Low Limit Screw

To six low limit screw, repeat the same process described above for high limit screw. Use an Allen key to fine-tune the limit screw.
For setting a low limit screw, you’ll have to pedal your bike on the stand and manually drive the rear derailleur into the lowest gear. Just ensure that the derailleur enables the chain to find its way into the first gear with ease.
Rotate the low limit screw towards your right to move the rear derailleur towards the tinier cogs and vice versa.
Next, line up the top idle derailleur pulley with the lowest gear (largest cog).
Rememberadjusting the limit screws doesn’t affect the way rear derailleur’s index through the gears, they only controlthe derailleurs travel in either direction.

Step #5 Install Shifter Cable and Cable Housing

You can install the shift cable once your rear derailleur is set up. This enables you to join the rear derailleur to the shifter. Here’s how it’s done:

Make sure that the shift cable is installed correctly to the frame and the routing and/or housing doesn’t constraints its movement.
Next, release the cable out of the shifter by moving it into the hardest gear setting.
To tighten it, rotate the barrel adjuster towards your right.
Then, pull the cable using a pair of pliers and secure it to the bolt lock of your rear derailleur with an Allen key.
Move the crankset while pedaling through the gears of the sprocket or cogs to check whether it shifts properly.
Repeat the steps outlined above till there is no more slack left in cable, leaving you with a properly shifting derailleur.
Using a cable cutter, cut the excess cable. Don’t forget to attach a cable end to it.

Step #6 Fine-Tune the Rear Derailleur

Now it’s time to make some final modifications to make sure the chain indexes through each gear seamlessly.

To adjust the cable tension, use the barrel adjuster located near the shifter. It’s important to note that moving the barrel adjust outwards escalates the cable tension, making it easier for the chain to index up into a simpler gear.
In contrast, moving the barrel adjuster inward reduces the cable tension, making it easier for the chain to index down into a harder gear.
While pedaling your mountain bike, begin in the highest gear and turn the rear derailleur up one gear at a time. In case the chain falters to shift into a larger cog, increase the cable tension.
Keep fine-tuning the cable tension until the rear derailleur shifts up and down effortlessly.

Read Can Mountain Bikes be Used on Road?

How to Install A Rear Derailleur on A Mountain Bike: Conclusion

Following these six steps will enable you to make the most out of your mountain bike ride.

Installing a new rear derailleur will not only allow you to get the right momentum and shift gears easily. It can also help you drive faster and position you in better control of your mountain bike on adventurous terrains.

Lucky for you, removing and installing your mountain bike’s rear derailleur isn’t very demanding.

Just remember, like every moving bike component, the derailleur also benefits from regular maintenance and cleaning.

Additionally, frequent lubrication of the working surfaces of the rear derailleur can also extend its life and ensure shifting remains smooth and quiet.

Nevertheless, the best thing about this process is that it can enhance your overall biking experience.

Hit the track and try it out yourself. You will know what we are talking about!

So, that’s it for today. We would love it if this blog post on “How to Install A Rear Derailleur on A Mountain Bike” helps you in any way possible.

Let us know if you have any queries and, more importantly, if there is more to add! If you are in search of more useful tutorials like this one, be sure to check the rest of our blog.