If you’re an active biker, sooner or later you’ll run into a problem that the bike’s rear derailleur has lost its function of shifting gears as it should do.
This can be due to many reasons, which we’ll deal with in this article.
The sooner you learn to adjust and change the rear derailleur, the better. You’ll be able to do fine-tuning, instead of running to the nearest mountain bike service center.
Is it hard to replace the rear derailleur?
It’s not a problem to install a new rear derailleur or to change it if you have the required utensils, and if you even slightly understand how a rear derailleur works.
A rear derailleur is a very important detail of the drivetrain. To alter gears properly, check if your mountain bike’s rear derailleur is in excellent shape.
As nowadays bikes are created with a lot of speed gears, their systems of braking are more complicated. That’s why derailleurs are necessary.
There are front derailleurs and rear derailleurs.
We are going to find out how to install a rear derailleur. The rear derailleur begins working whenever you start riding your bike, go up a hill, or stop, in other words, when you move from a lower gear to the higher one.
This important part of the bicycle works constantly and therefore can fail.
Rear derailleur’s short description
What’s the rear derailleur, and what function does it have? It’s the machinery of a mountain bike that changes the place position of the chain from the smallest sprocket to the bigger one, or vice versa, and regulates the speed.
Derailleurs are commonly attached to the bike’s derailleur hanger with a titanium mounting bolt. Rear derailleurs are divided into three kinds (short, medium, and large) and we can single them out by the cage’s length.
In outdated mountain bikes, you are likely to find the standard derailleur. But on e-bikes and some road bikes, you are more likely to find the electric derailleur.
How to define the time to change a rear derailleur?
Examine the rear derailleur systematically and listen to how it works.
If everything is fine, the rear derailleur works silently.
But if you hear a noise from the shift, something is wrong, and you have to correct the rear derailleur.
If all corrections don’t help and the noise doesn’t disappear, think of changing the old derailleur.
Other arguments to replace or install a rear derailleur
- The chain should not break off.
- The chain line should be exactly along the ring chain.
- Garbage can get inside and wrap throughout the chain and rear derailleur.
- The derailleur cage should not constantly chafe against the connecting rod.
These arguments are a cause to examine the rear derailleur and change it if it’s worth doing.
Besides, regular and timely inspections will help to avoid serious breakdowns and accidents.
Reasons that can lead to a breakdown.
- The switch may extend beyond the largest cog in case the lower limit screw is set incorrectly. Thus, the bicycle spokes can over shift.
- After an accident, the hanger can be somehow curved. It can also happen after the bike falls directly on the side where the derailleur is.
- The rear derailleur can be also within a factory fault.
- If the derailleur is not of a high quality, there is more likely a weak place and even a little oscillation during the trip break derailleurs.
- The old rear derailleur mechanism has worn out and failed.
- Debris wounds on the chain and accumulated within the derailleur can disrupt or break the rear derailleur.
Stage of preparation to install a new rear derailleur
If you dare to install the rear derailleur yourself, seize all appliances in advance and get to work.
It’s best to take a set of tools designed specifically for mountain bikes.
If you don’t have a kit, grab a few tools that you have in your household or that came in a kit to your bike: a bike stand, Allen keys, screwdrivers, cable cutters, and chain pliers.
Stages of how to install a rear derailleur properly
A quick visual inspection will help you to identify the issue with your rear derailleur. When you find the issue, you can replace the derailleur with a new one.
Stage 1 (Remove an old rear derailleur)
- Inset the mountain bike into a special bike stand.
- Move the chain to the smallest rear sprocket.
- Pull off the shift cable’s end cap to disjoin the shift cable.
- Weaken the cable pinch bolt and remove the shift cable from the rear derailleur.
- Now it’s time to remove the chain from the shifter. Some circuits have a special connector pin that you must replace.
- If you’re not planning to remove the chain to clean or replace it, then just remove the lower jockey wheel and turn the cage plate to release the chain. If you’re going to remove the chain, disjoin a link with a chain tool and pull the chain through the top pulley.
- Look attentively to find a master link and remove the rear derailleur easily, not breaking the chain during installation. (The master link helps to join and disjoin the chain line, not using a chain break tool). If the master link is not provided on the chain, then you cannot do without a chain tool.
- Turn the derailleur against clockwise and remove it. You can unscrew the derailleur’s mounting bolt.
Stage 2 (Install a new derailleur)
- Look attentively if the current derailleur hanger is in the upper position.
- If something is wrong with the derailleur or the hanger, replace them, and therefore install the new derailleur.
- Quickly examine if the threads are not deformed and without shortcomings.
- Fit up the derailleur’s mounting bolt, turn it against clockwise, and tighten it without moving it from its place.
- Put the chain back on.
- Install the limit screws.
- Set the high limit and low limit screws. (They confine the derailleurs’ movements in both directions).
- Set the high-limit screw first. Take the Allen key and turn to move the derailleur toward the bigger cogs.
- Set the low-limit screw then, turning the Allen key and moving the derailleur toward the smaller cogs.
- Insert the shift cable back into the derailleur. Pull it closely and tighten the anchor bolt so the cable flattens.
- Install the new derailleur, tighten it too with the anchor bolt, and probe it. Look from behind to check if the upper jockey wheel is in line with the smallest cog.
- The cable tension must be even. Avoid its slack. That’s why pull it closely, tight again, and fix it with a cable pinch bolt.
- If you tightened the cable not enough, and it even hangs a little, use a cable cutter to cut an excessive part. Clutch it with a shift cable’s end cap, then. Ride the bike around to be sure that everything is installed correctly and working right.
Is it easy to replace the derailleur? Summary
You’ve read the exact procedure of removing and installing the rear derailleur, and now it’s clear how to install a rear derailleur correctly. Besides, the instructions are suitable for a mountain bike as well as the road bike, as the difference between the two bikes is not so big.
It’s quite easy, especially if you own all the required tools. If you haven’t them, think of getting a set of tools from a bike shop.
It’s worth noting that knowing how to install a rear derailleur or fix another breakdown of a mountain bike is good, but it’s better to take care of it and prevent all potential troubles.
How to prevent rear derailleur failure?
Clean and maintain the bike regularly to provide its long working life. The derailleurs become muddy very fast because the bike chain is lubricated with oil, and the jockey wheels are as if attracting dirt on it.
A few simple steps to maintain your bike:
Regularly spray the chain with a degreaser. A good degreaser makes its job great and removes the greasy dirt easily, so you don’t need to dismantle the derailleur to make it clean.
As a last resort, use a brush to clean the mud from the derailleurs’ cages.
Use a screwdriver to scrape dirt off the support wheels, then wipe clean.
The jockey wheels and any other mechanical detail can wear out after a while and have sharp edges. Replace them if you notice them. If the wheels are in good shape, rub the lubricant onto them.
Mountain biking is fun and environmentally friendly, just like living and traveling in an RV. But if installing a rear derailleur, tightening the chain, or changing any other detail that failed is a serious issue, it’ll be a bit problematic for you to apply to a service center every time.
The faster you’ll learn to do it yourself, the better!