Have you ever had unexpected problems using the rear derailleur of your beloved bicycle? It is a small misadventure that sooner or later all owners of a mountain bike or racing bike experience. Many people are afraid of trying to adjust the rear derailleur of their bike themselves to avoid making the situation worse. However, it is good to know that this is not an activity that can only be performed by the experienced staff of a bicycle shop, you simply need to learn how to adjust the rear derailleur so that it resumes working properly. This operation should be performed regularly, as the mechanical stresses to which this very important component is subjected lead to a loss of optimal adjustment. All it takes is a little bit of dexterity and lubricant.
Steps
Method 1 of 2: Troubleshoot the Gearbox
Step 1. Position the bike so that the rear wheel is free to turn during the adjustment work
You can choose to place it on a special stand or to turn it over and place it on the ground on the seat and on the handlebar. To adjust the shifting, you need to be able to spin the rear wheel freely to be able to shift.
Step 2. Engage the highest speed (or gear) possible
This is the smallest gear in the cassette or rear sprocket. It is the gear furthest from the rear wheel hub. The rear derailleur is equipped with a cage composed of two small toothed wheels, vertically superimposed, whose purpose is to always keep the chain in tension. When the highest available gear is engaged, the tension exerted on the chain is as low as possible. This means that the gearbox is doing minimal work and is therefore the ideal situation to make adjustments.
As you spin the rear wheel by manually turning the pedals, locate the cable that goes to the rear derailleur from the handlebar and gently pull it. Notice how, as you increase the cable tension, the front derailleur automatically shifts. All that needs to be done for the gearbox to function properly is to find the appropriate tension of its control cable
Step 3. Locate the cable tension adjustment screw, then follow the shift cable back for any damage
The rear derailleur cable tension adjustment screw is a small stainless steel cylinder attached to the derailleur rocker where the wire from the handlebar enters. Follow the path of the cable starting from the rear derailleur and going up to the handlebar of the bike. The tension of this steel cable is what really allows the front derailleur to shift. Make sure it is properly installed in its seat and that there is no fraying, deformation or kinks in any point. These are problems that happen very rarely, but which are still best ruled out.
Step 4. Try shifting all gears in both directions and see if there is any problem
Without stopping pedaling, change one gear at a time using the gear lever. Make a mental note of all the times the chain skips a speed or a double press of the shift lever is required to shift. Does the problem manifest itself when going up or down? When the wheel turns, do you hear an abnormal noise or does the chain tend to jump?
Step 5. Shift into higher gear, then shift down into lower gear until you accurately locate the area where the problem you found in the previous step is occurring
For example, if your bike is having a hard time shifting from fourth to fifth speed (or gear), shift the chain to the fourth rear sprocket gear. At this point, continuing to pedal, act on the waist that adjusts the tension of the cable by rotating it in the direction required by the adjustment to be made. Normally, tightening the screw decreases the tension while unscrewing it increases. In this case, the adjustment screw must be unscrewed, i.e. rotated counterclockwise. In this way, the tension of the derailleur cable increases triggering the gear shift.
Note that since the bike is upside down, you have to turn the adjustment screw in the opposite direction to where the chain is to be moved
Step 6. Turn the adjusting screw counterclockwise to help the chain shift from the highest to the lowest gear, ie moving towards the larger gears
By increasing the tension of the rear derailleur cable by unscrewing the appropriate adjustment screw, the passage of the chain towards the lower gears, that is towards the larger sprockets of the pinion, is facilitated. If nothing happens when shifting gears, leave the shift lever in the chosen position and continue pedaling, then turn the derailleur cable tension adjustment screw counterclockwise until the chain is able to "climb" onto the desired sprocket. At this point, the adjustment is finished.
Step 7. Turn the shift cable tension adjustment screw clockwise to cause the chain to shift up to the smaller gears
If the chain struggles to move into the higher gears, i.e. the smaller sprockets of the sprocket, the adjustment screw must be tightened to release the tension. If nothing happens after operating the gear lever, continue pedaling while turning the adjustment screw. Tightening the latter loosens the tension on the shift cable allowing the chain to move into higher gears. Slowly turn the adjusting screw until the chain fits over the desired sprocket.
In the event that the chain has "skipped" a gear by moving two gears with only one downshift, it is necessary to screw the adjustment screw to decrease the tension of the derailleur cable
Step 8. Check the engagement of all gears in both directions by slowly shifting one speed at a time
Once the derailleur has been adjusted, so that the engagement of a single gear is done precisely and smoothly, the rest of the shifting should also happen without any problems. Check all speeds to make sure the setting is correct. If the problem persists:
- Fully tighten the adjustment screw to loosen the shift cable as much as possible (approximately 2-3 full turns), then repeat the procedure. If at the beginning of the adjustment the cable that controls the movement of the derailleur still seems too tight, it must be adjusted from scratch.
- Check that there are no deformed gears and that the derailleur cage has not damaged. If these measures do not solve the problem, it means that it is more serious than expected.
Step 9. Lubricate the screws and moving parts of the front derailleur using a suitable bicycle product to prevent similar problems in the future
Keeping the chain well lubricated using a special product ensures that the links remain perfectly mobile, thus facilitating gear changes.
Method 2 of 2: Avoid Falling the Chain
Step 1. This step must be performed if the chain comes out from one of the two sides of the rear sprocket by turning the screws that adjust the limit switch of the derailleur
There are two screws called "L" and "H" on the gearbox rocker, whose purpose is to limit the movement of the gearbox once it reaches the limit positions. Basically, they determine the maximum limit that the chain can reach both towards high and low gears. Unless there is a frequent fall of the chain outside the rear sprocket, there is no reason to adjust these two screws (normally, they are adjusted correctly by the manufacturer). However, if you have experienced a fall or have had to completely replace the rear derailleur, you may need to readjust both end stops.
- If the chain frequently slips off the rear sprocket, check the screws that adjust the stops.
- If you can't shift into higher or lower gear, check the limit switch screws.
- If the chain hits the bicycle frame, check the correct adjustment of the limit switch screws.
Step 2. Turn the "H" screw of the lower limit switch clockwise to prevent the chain from shifting excessively to the right side of the sprocket
Conversely, turn it counterclockwise if the chain fails to engage in the highest gear. The limit of the lower limit switch refers only to the smallest gear of the rear sprocket.
Step 3. Turn the screw "L" (relative to low gear, from English "Low") of the upper limit switch clockwise to prevent the chain from moving excessively on the left side of the rear cassette and risking crashing into the wheel
Again, if the problem is that you are unable to engage the lowest gear available, you must turn the limit switch screw counterclockwise. The limit of the upper limit switch refers only to the largest gear of the rear sprocket.
Step 4. Engage the highest gear first, then the lowest gear, to visually verify that the gear cage is perfectly aligned with the respective gear
Once the limit switch limits are adjusted as desired, make sure the alignment of the derailleur cage is correct. The two pulleys inside the rear derailleur cage should be perfectly aligned with the gear of the engaged gear.
Step 5. Test the adjustment of both limit switch screws, "H" and "L", to see how the cage actually moves, as a result, of the derailleur
When the highest or lowest gear is engaged, by acting on the respective limit switch screw, the derailleur will move accordingly. If you need to change the upper limit switch limit, engage the lowest gear, i.e. the one that corresponds to the largest gear of the rear sprocket. At this point, turn both limit switch screws half a turn to check which of the two triggers the movement of the gear cage. Make sure that the rear derailleur is perfectly aligned with the center of the gear of the engaged gear, then restore the original position (turning it half a turn in the opposite direction to before) of the limit switch screw that did not generate any movement of the gearbox cage. This last expedient serves to avoid losing the correct adjustment of the other limit switch limit (in this case the lower limit).
Advice
- All adjustments should be made gradually.
- Before starting, always check that the dropout (the component or point on the frame where the rear derailleur is mounted) is not bent. If so, before proceeding with any adjustment, it is necessary to restore its original shape and position (in the case of a removable dropout that is seriously damaged, it can be considered to replace it).
- The procedure to follow to adjust the front shifting of a bicycle is practically identical to that described in the article.
Warnings
- Incorrect adjustment of the rear derailleur can cause difficulty in shifting or a hopping or falling of the chain while driving; in extreme cases, it is possible that the frame will be damaged or the gear cage may end up between the spokes of the wheel.
- Performing this procedure without having the necessary bicycle experience can be difficult. If in doubt, contact a bicycle shop and ask if you can have the assistance of an experienced professional to show you how to adjust the rear derailleur.
