How to Install a Rear Derailleur

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You’re out on the trail and suddenly your rear derailleur is not shifting through the gears as it should. Don’t summon for help just yet. If you know how to install a rear derailleur you can do it yourself in a few minutes.

What is a Derailleur and Why Does it Matter?

But first things first; why does your derailleur matter? It is the mechanism that shifts the chain from one gear to the next. When you press on the brake lever, the gear shifter on the handlebars pulls on a cable that moves the derailleur, which moves the chain into the matching cog.

The derailleur is the most important part of the drivetrain and it works quite hard. If you want to be able to shift gears with ease, your derailleur needs to be in good working order at all times.

Bikes in the past had few gears so they didn’t really need derailleurs. The chains ran on one cog and gears would change in the hub.

However, today’s bikes come with a lot of gears – some as many as 21 – and the braking system is a tad more complicated. Hence the need for derailleurs.

The name comes from the fact that they “derail” the chain. Today’s bikes have front and back derailleurs. The front derailleur moves the chain between the chainrings while the back derailleur moves the chain between the sprockets of the rear wheel.

These are the derailleurs you use the most. Think of them as you would the brakes in a car. They are your lower gears. It’s easier to pedal or drive in lower gears. On a bike, your rear derailleur comes into play every time you set off, when you’re coming to a stop and when you’re cycling up an incline.

You also need them as you build up speed as you move from lower to higher gears.

Check out How to Install Front Derailleurs

You want to be able to change gears as smoothly as possible, and that’s why your rear derailleurs should be in working order at all times.

If you’re used to doing your own maintenance and bike repairs, you’ll find that installing a rear derailleur doesn’t really require a mechanic.

However, if you’re not the DIY type, you may want to wait until you can get professional bike repair. DIY rear derailleur installation isn’t advisable if you’re not sure of what you’re doing and if you don’t have the right tools. You may end up causing damage that will cost money to fix.

How to Install a Rear Derailleur

What Causes a Derailleur to Break Down?

There are several reasons you may find yourself needing to replace a rear derailleur:

  • Over-shifting: when the derailleur moves beyond the largest cog because it was improperly set.
  • When the bike falls over and the hanger gets bent.
  • Cheap derailleurs will almost always be problematic. They come with factory defects and you can expect them to break down before long.
  • Simple wear and tear will cause a derailleur to break down.
  • Debris is another common cause of derailleur failure.

Let’s get on to how to install a rear derailleur.

Installing Rear Derailleur

What Tools Do You Need?

These tools are available on Amazon. You can also check-in hardware shops near you.

Step 1: Remove the old derailleur

  • To do this you need to put the bike up on a bike stand and then move the chain to the smallest cog.
  • Next, pull off the shift cable’s end cap and loosen the pinch bolt. This removes the cable from the derailleur.
  • After that, you need to remove the chain from the derailleur. You do this by locating the master link. It has an easy release that helps you disconnect the chain easily. If the chain doesn’t have a master link use the chain tool.
  • To remove the derailleur go counterclockwise and unthread the mounting bolt.

Step 2: Installing new derailleur

  • Check the derailleur hanger to make sure that it isn’t damaged. You don’t want to install a new derailleur on a damaged hanger.
  • Mount the new derailleur on the mounting bolt by turning it anti-clockwise. Once it’s in place tighten the bolt.
  • The next step is to put the chain back on.
  • You can now put the shift cable back in the derailleur. Make sure it’s tight and then tighten the bolt to flatten it into place.

Step 3: Adjust, finish and test

  • Now that the old derailleur is out and the new one is in, it’s time to adjust and test it. To do this, you need to limit the high and low ends of the screws to make sure the derailleur doesn’t move beyond the set limit. The upper jockey wheel should be in line with the smallest cog when you check it from behind.
  • The cable should be seated and have no slack. Pull it tight and then re-tighten it to get rid of all slack.
  • If you need to, trim the cable and then use a cable end cap to crimp.
  • Test to make sure everything is working as it should.

Check out How to Tighten a Bike Chain

How to Clean and Lube Derailleurs

Keeping your rear derailleurs clean helps them last longer. They get dirty fast – remember their job is to support a greasy bike chain. They also get a lot of dirt and debris thrown at them from the wheels.

If you want derailleurs to last you have to clean and lube them on a regular basis. Here’s what to do:

  • You don’t need to disassemble to clean the derailleur. Spraying with degreaser works. There are many types of degreaser in the market, and you can find some of the best here.
  • The cages of derailleurs collect a bit of dirt. To get rid of it use a brush. Some people prefer to remove the chain to get this done but you can do a good job with it still on.
  • The jockey wheels tend to cake with grime. You can scrape it off gently with a screwdriver and then wipe it off with a rag.
  • Check the jockey wheels. They wear out over time and eventually develop into little spikes-like teeth. If you find they are no longer blunt you should replace them. If they don’t need replacing you should apply a bit of lube. Make sure to choose a lube that’s appropriate for the current weather.
  • A rear derailleur has 4 pivots and they need to be greased from time to time. If they start to stick they can lead to poor shifting. Apply a bit of lube and then move the machinery around to help the lube settle into place.

Check out How to Remove Rust from Bike Chain

Winding up on How to Install a Rear Derailleur

If you learn how to install a rear derailleur you don’t have to pay someone to do it for you. It’s a relatively simple process that takes a short time.

Assemble the necessary tools, get some good quality lube and some rags to wipe down parts. A good mount is a great addition to your toolkit but if you don’t have one you can turn your bike upside down and lean it on a wall. Make sure it’s firm so it doesn’t fall over as you work.

I understand that things like rear derailleur installation may not be everyone’s cup of tea. If you feel it’s too much for you pay your local bicycle shop to do it for you. In addition to installing rear derailleur ask them to do overall maintenance to ensure your bike is ready for riding.