How to refurbish an old rear derailleur

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A step-by-step guide to rejuvenating an old rear mech

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Shimano is a bike component manufacturer based in Osaka, Japan. The company is one of the industry’s most popular manufacturers and it makes up around three-quarters of the bicycle component market by value.

Over time, even the best kept components need some love, and nowhere is this more the case than a rear derailleur. No matter how well a rear derailleur is looked after, over time it is going to need some attention to keep it running smoothly. A derailleur that needs to be refurbished will have an effect on how your bike feels and how well the shifting of gears actually is. Here we are going to run through a step-by-step guide on how to bring some life back to an old rear derailleur.

There are a few components within the rear derailleur that we can take a look at restoring to their former glory, they are:

To do all this we will need a few microfibre cloths, some small brushes, degreaser, isopropyl alcohol, grease and a selection of hex keys along with a small flat head screwdriver.

If you want to find out more about groupsests and which one can offer you what you are looking then make sure to check out our complete guide to groupsets.

How to Steps

Clean external parts and surfaces

Remove main cage from derailleur body

Inspection

Remove remaining parts from the main body

Removing the main pivot bolt

Clean the main body

Reassembly process

Tools Needed

Step 1

Clean external parts and surfaces

To do this you are going to want to remove the pulley wheels and the rear portion of the cage from the rest of the derailleur. This will really allow you to reach all the areas that are going to need a good clean. To remove the pulley wheels and cage you will need to remove the two small hex bolts (typically 3mm) that hold them in place.

Once the parts are removed, using a degreaser or soapy water solution and a brush remove as much of the dirt and grease as you can. Repeating this a few times if the derailleur is particularly tired and dirty will give you the best results. Allowing the parts to soak in warm soapy water for a few minutes can also help to loosen that ingrained surface grime.

Step 2

Remove main cage from derailleur body

When removing the main cage from the rest of the derailleur it is important to take care, as this component is under tension from a tensioning spring. This is what keeps your chain tight in any gear so releasing this preload needs to be done carefully. Cleaning this area out and packing it full of a thick all-weather grease will protect this pivot from premature wear. Any grit or dirt that makes its way into the main cage pivot will accelerate wear drastically.

Before you remove the cage completely, it is best to take a few close up photos of how the spring is fitted to add tension as well as where the locating tabs sit on the derailleur body. As you undo the 5mm hex bolt that is holding the cage on, keep some of the spring tension on by holding the cage up with your thumb. This will prevent the cage from springing off unexpectedly.

Step 3

Inspection

Once the cage has been separated from the body it is time to inspect everything for wear and damage as well as giving everything a good clean with the degreaser to remove any built up dirt and grime from the cage and the spring itself.

The small plastic bushing that sits between the cage and the main body can also be cleaned up and degreased, there is a small recessed ring on the outside of the bush that can hold a lot of built up dirt. Using a flat head screwdriver can be useful for getting into this to remove all the dirt.

Top Tip

If there is any sign of corrosion or surface rust that doesn't look to be too significant a bit of emery cloth or some very high grit sandpaper can be used just to remove the corrosion until clean metal is showing.

Step 4

Remove remaining parts from the main body

Now is a good time to remove all the other parts that can be easily removed from the main body.

The barrel adjuster can be removed simply by just unscrewing it from the body, taking care to keep all parts and the small spring together once removed. At this point the limit screws can also be fully removed with a small screwdriver and kept safe.

Step 5

Removing the main pivot bolt

The main pivot bolt is also under some spring tension so care and attention should be taken when removing it. To do so, you want to locate the retaining clip on the bolt itself and work the clip round with a small screwdriver until the small slot points up. Once the clip is correctly oriented you can use a flat head screwdriver to pry the retaining clip away from the bolt.

Holding the main pivot and the body separately, slowly remove the spring tension it is under in a very similar manner to the cage bolt. Once the tension has been removed the main pivot bolt can be removed from the main derailleur body and undergo the same cleaning treatment as the main cage section did previously.

Step 6

Clean the main body

Now that everything that can be removed from the derailleur has been removed, it is time to give the body a deep clean, really focusing on the areas around where parts have been removed.

Step 7

Reassembly process

The reassembly of the rear derailleur follows the reverse order of the above steps, with a further clean and inspection of any parts that you feel might need a little bit more love as you go.

The most important part of the assembly process for a rear derailleur is ensuring that tension the system are refitted correctly and located in the holes in the associated components.

Once the system has been reassembled with the main pivot bolt and the main cage refitted, take a clean cloth and wipe away any excess grease that might be on the surface of the derailleur as this will hold dirt and grit.

The final step is to add some of the assembly grease to the bushings in the pulley wheels and then reassembly the pulley wheels and the rear section of the cage.

Top Tip

Before continuing on to the reassembly process, clean up the working area so that there is no chance of any dirt being reintroduced to the system as it is getting rebuilt. A thick bike specific assembly grease should be used throughout the assembly process to lubricate moving parts as well as acting as a barrier to prevent dirt and water making its way inside the working parts of the derailleur.

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