The rear derailleur will become worn with use and abuse. As the
derailleur wears, it will develop play at all pivot points. Grab
the cage at the lower pulley of a new derailleur while mounted to
a bike and wiggle it side to side. Do the same test on an old model
to compare. Replace derailleur when this play becomes significant.
The derailleur pulleys will wear and eventually require replacement.
The teeth will thin and become pointed, especially the lower pulley.
Worn pulleys will not be able to hold or guide the chain as well
as newer pulleys, and shifting performance will suffer. In the image
below, three pulleys are shown in progression of wear. Pulley bearings
or bushings will also wear and create more play in the pulley.
Rear Derailleur Overhaul and Pulley Cage Tension
Level of Difficulty: Advanced
Typical Tools and Supplies Needed 
- Hex wrenches
Screw drivers, narrow straight blade and #2 Phillips
Work tray for small parts
Seal pick (optional)
Bench vise (optional)
- Degreaser for cleaning small parts
- Light lubricant
This article will discuss the overhaul of Shimano® and Campagnolo® rear
derailleurs, which share many service features. The internal overhaul
rear derailleur will also be discussed.
will also be reviewed, although
user service is limited. It should be noted that every model of every
brand cannot be overhauled. See also related articles:
Some rear derailleur models allow the internal servicing in order to
clean and lubricate. This often improves performance by removing dirt
from pivots. Additionally, some models allow for the changes to the pulley
cage tension spring. There are also after-market top pivot "break-away"
bolts, which may be installed in place of the orgininal mounting bolt.
It will be useful to have a note pad and pen to help you remember correct
orientation of parts. Sketch any parts that seem unfamiliar, or use a
digital camera for the same purpose. Have some wire ties or twine on hand
to help tie parts in their correct orientation as they come apart.
Begin by removing the rear derailleur from the bike. Loosen inner wire
pinch bolt and pull inner wire from adjusting barrel. Remove the chain
if it has a master-link. Loosen derailleur mounting bolt and remove derailleur
For bicycle chains with no master-link, the cage may be dismantled, which
allows the chain to stay together. Note and record any marking distinguishing
upper and lower pulley. Also note the orientation of the cage. Loosen
and remove both derailleur pulley bolts. Remove the cage and chain from
The derailleur may contain a tension spring in the upper pivot, at the
mounting bolt. This spring controls the angle of the derailleur body.
The mounting bolt spring and cage pivot spring oppose one another. Changing
tension in the upper pivot relative to the lower pivot will move the derailleur
body and upper pulley wheel relative to the cogs. Generally, it is desireable
to have the upper pulley ride close to the cogs. Check the cog to pulley
position when the chain is on the largest rear cog and the smallest front
ring. If the largest cog is actually rubbing against the upper pulley,
move the derailleur body back to move the pulley away. For derailleurs
with the spring in the upper pulley, increase the spring tension by tightening
the "B" screw, found in adjacent to the top bolt. If there is a large
gap between pulley and cog, the screw should be loosened.
Generally, the upper pivot spring tension should not be increased to
solve the problem of chain slap or chain suck. Chain slap may be reduced
slightly by this procedure, but chain suck is typically the result or
worn or bent chainring teeth, or a worn chain. Increasing the derailleur
cage tension tends to have a marginal effect of chain suck. For chain
slap, it is preferable to increase the tension of the pulley cage. There
are limits to this procedure, as the upper mounting bolt spring tension
opposes the cage spring tension. Increasing the cage spring tension will
require an increase in the mounting bolt spring tension. If the derailleur
B-screw is at it's limit, it is not adviseable to increase cage tension.
Campagnolo® derailleurs locate the B-screw in lower cage pivot. The upper
spring tension is fixed. Tightening the B-screw will increase tension
of the cage, allowing the pulley to move toward the cogs. Loosening the
B-screw will decreases spring tension at the cage, allowing the upper
pulley to move away from cogs. The screw turns a toothed plate that holds
the spring end.
Prodedure for Derailleur Overhaul
(most models of Shimano® and Campagnolo®)
Use a thin tipped screwdriver to pry off the C-clip on the back
side of the derailleur mounting bolt. Work over a table to avoid losing
parts. Maintain pressure on the B-screw plate against the body while removing
the clip. This helps prevent parts from flying off as spring tension is
Remove the lower cage from the derailleur body. There are several
different systems of cage attachment. Many models from Shimano® use a
screw under the body, called the P-screw. This screw holds a stud mounted
to the pulley cage. To prevent premature release of cage spring tension,
hold derailleur cage firmly to derailleur body and remove this screw using
Alternatively, there may be a set screw in the derailleur cage that acts
as a stop. Pivot cage away from stop, and remove set screw, then allow
derailleur to unwind. Note direction cage unwinds for re-assembly.
For P-screw type derailleurs, hold both derailleur body and
derailleur cage. Pull cage away from body and allow cage to unwind. Note
direction the cage unwinds.
The derailleur cage may be held to the body with a pivot bolt. The bolt
head may face toward outside, away from the spokes, or it may face inside,
facing the spokes. Loosen and remove bolt. Note and record any washers
or seals found on bolt or on cage.
As cage is removed from body, make note of the spring hole in
the derailleur cage and body. There are commonly two or more hole choices.
New derailleurs are typically assembled with the spring in the hole that
allows the most relaxed postion of the spring. If more cage tension is
desired, the spring end can be installed in the other hole.
Remove spring from inside derailleur body. Note especially the
direction of the coil ends. The smaller end tends to face toward the derailleur
cage, and the larger end goes into the derailleur body. There is commonly
a seal as well. Note direction of lip.
If derailleur cage is still together, loosen and remove one
at a time each pulley bolt. It is common for the upper and lower pulleys
to be different. Do not mix parts from upper and lower pulleys. Upper
pulley may be labeled as "G" pulley, or simply "upper".
Note parts orientation of cover plates, seals, and bushing. Use a wire
or string to tie these parts together in the correct orientation.
Some pulleys have have a cartridge type bearing. Use a seal pick to carefully
lift the seal from the inside edge.
Clean all parts with degreaser and dry. Use compressed air if
possible, but do not allow bearings to spin.
on pulley bushings and seals. Assemble pulleys into cage
in the same orientation as they were dissassembled. Remember to refer
to your notes on orientation. Install and tighten pulley bolts to about
30 inch-pounds. Use of a mild
Cover both springs heavily with grease.
Install cage spring into derailleur body, with smaller tapered
end of spring facing outward toward cage. Be sure to engage spring into
spring hole inside body. Place dust seal over derailleur body as it came
Engage cage spring into derailleur cage and body. Again refer
to notes from disassembly. Changing spring hole location will change tension.
In the image below, spring is in most relaxed position. Seen from this
orientation, cage will be rotated counter-clockwise for working tension.
In the image below, the spring is engaged in the higher tension spring.
Notice cage must now be wind futher counter-clockwise, adding to spring
Press cage into derailleur body and begin to rotate derailleur
cage toward back of derailleur. It is important to always wrap the spring
tighter in the same direction as the coil.
Looking at the back side of the derailleur (opposite side of brand name)
rotate cage clockwise to tension spring.
For P-screw type derailleurs, cage stop and derailleur body
stop must clear. Pull slighlty outward on cage and allow the two stops
to pass. Push cage fully into derailleur body once stops are cleared.
For bolt type pivots, rotate cage until you can access stop
For P-screw type, re-install set screw into derailleur body.
Mounting bolt spring can be difficult to engage and tension.
It is useful to mount a hex wrench with the short "L" facing upward in
a vise. The vise and wrench act as a holder and frees up your hands.
Install spring into body in same orientation as it came apart.
Note direction of spring coils, which will indicate the direction of tensioning
spring. Place dust seal over spring. Engage body tension plate on spring.
Press plate fully down to see if plate will fully engage system.
Using needle nose pliers, grab body angle screw.
Again, tension spring with direction of wrap. Upper pivot springs
wrap counter-clockwise. Rotate plate counter-clockwise to tension spring.
Pull plate upward enough to clear stop tabs on each.
Push downward on plate and hold pressure downward before installing
Install C-clip onto mounting bolt. Use needle nose pliers to
fully engage C-clip.
SRAM® X.0 Derailleurs
The X.0 derailleur may be overhauled at the lower cage
pivot. The mounting bolt has no spring, and it is best to leave this bolt
in place. No lubrication of the mounting bolt pivot is recommended.
The SRAM® parallelogram spring is very strong. It is
possible to use a zip tie to hold the derailleur body away from the cage,
making it easier to work with the cage. Feed a zip tie through the body
below the cable stop, and through the cable guide. Pull the cage away
from the body as if shifting toward larger cogs, and secure the zip tie
to hold the body.
Lower pivot overhaul procedure
Rotate cage to expose the cage stop screw. Loosen and remove
the stop screw. Cage will now rotate back past the stop screw position.
Allow cage to rotate forward and relieve spring tension. Note
position of cage to derailleur body in this relaxed position.
The pulley cage is held to the body with a stud pressed into
the cage. The stud has a "D-fitting", that mates with a D-shape recess
in the body. The body must be rotated to one position only before the
cage can be removed.
There are three tension options in the cage, as seen in image
above. The middle spring hole is used on new derailleurs. To decrease
chain slap, increase spring tension by moving spring to left hole of the
three choices, as seen from the stud side.
After removing the pulley cage, loosen and remove pulley bolts.
Pulleys use a cartridge bearing, use care when removing seal.
6 Clean all parts with
grease into seals of pulleys and re-install seals. Pack grease into
cage pivot spring.
Assemble pulley wheels into cage and install pulley bolts. A
mild threadlocker is recommended on the threads. Spin pulleys to check
proper for alignment after securing bolts.
Place spring into body of derailleur in same orientation as
it was removed. Engage spring end into desired cage hole.
Push cage to derailleur body. Cage must rotate to allow "D"
fitting to engage into body. Approximate position of cage to body for
"D" fitting alignment is shown below.
Rotate cage counter-clockwise as seen from orientation of image
above. Install and secure cage stop screw. Remove zip tie. Derailleur
is ready to be installed.
The Mavic® Mektronic derailleur has many internal parts, including
electronic parts. There are very few user serviceable parts. The pulley
wheels can be brushed clean with a dry bush. Avoid using solvents during
There is a boot covering the arm that extends to shift the pulley cage.
Use only a soapy water on a rag to wipe this clean. Use care not get
water or soap into the working mechanism.
The derailleur uses a solenoid initiate the shift. It is activated by
a battery. The battery cover is removed using a 1-Euro coin (or US twenty-five
The derailleur B-screw is located at the top mounting bolt. There is
a spring in this pivot, but it is recommended the pivot not be disamantled.
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