Useful Tools and Supplies

• Repair Stand, holds bike secure for easy work.
• Hex wrenches as needed.
• Screwdriver (#2 Phillips or straight blade)
• Light liquid lubricant
• Derailleur cable inner wire and housing as needed
• Caliper or metric ruler
• Cable end caps and housing end caps as needed
• Rags

• Rear derailleur- limit screws and index settings
• Wire cable-sizing and cutting inner wire cable and housing (gear and brake)
• Brake and Shift levers
• Rear derailleur- overhaul
• Rear derailleur- bent hanger

Service Procedures

Front Derailleur Height

1. Inspect height alignment of front derailleur. The outer cage plate must be positioned over the largest chainring when viewing height. Simply grab the exposed front derailleur inner wire until outer cage plate is directly over outer chainring teeth. Use care to not shift the derailleur cage past this point. Note height and direction of change needed. It is then necessary to relax the cable to loosen the mounting bolt and raise or lower the height as needed.
2. The gap between the teeth of the outer chainring and lower edge of the outer cage plate should be 1-2mm, about the thickness of a penny. Using a penny or a dime as a feeler gauge, fit it between the chainring teeth and the cage plate. It should just fit between the teeth and plate. 
3. To lower cage, release inner wire tension completely by shifting to innermost chainring. Note angle of outer cage plate relative to chainring.
4. Front derailleur clamps typically leave a mark on the frame, which is useful as a reference when changing height. Loosen derailleur clamp bolt, change derailleur height, and return cage to same rotation relative to chainring. Tighten clamp bolt. Move outer cage plate over outer chainring, and check height again. Repeat this process until cage plate height is 1-2mm above outer chainring.

Front Derailleur Rotational Angle

1. Shift chain to outermost chainring and outermost rear sprocket.
2. Sight chain from directly above chainrings. Consider the chain as representing a straight line. Compare this line to outer derailleur cage plate. Outer cage plate and chain should be parallel. Keeping the cage and chain parallel will minimize the risk of the chain jumping off the outermost ring. If cage is not parallel, there will be a relatively large gap at either the back or the front end of the cage, and the chain may over shift.
3. If derailleur cage needs to be rotated, note direction of desired rotation.
4. Release inner wire tension by shifting to the innermost chainring.
5. Many clamps leave a slight marking on the frame. Use this scarring as a reference when changing height. It is also possible to use a pencil to make two reference marks on the frame, one for height and a second, vertical mark, to reference rotation. Use the marks to avoid inadvertently changing height.
6. Loosen clamp bolt and slightly rotate in correct direction. Use care not to change height. Tighten derailleur clamp bolt.
7. Shift to outer chainring and observe rotation alignment. Repeat adjustment if necessary.

Front Derailleur Limit Screw Settings

Front Derailleur - Adjusting L-screw

1. Shift chain to innermost rear sprocket and innermost front chainring. Inspect derailleur for marking indicating "L" screw.
2. Check inner wire tension. It should be fairly loose at this time. If inner wire is taut, turn barrel adjuster clockwise into housing. The barrel adjuster is typically located where the cable housing enters the shift lever. If barrel adjuster is already fully turned into housing, loosen inner wire pinch bolt, slacken inner wire and retighten bolt.
3. Sight gap between inner chain plate and inner cage plate. Only a small gap should be visible, about 1/16" or 1mm, about the thickness of a dime.
   
4. Pedal bike slowly and continue to sight gap. Set clearance at tightest point in chainring rotation. Adjust L-screw so there is a small gap between inner cage and inner chain plate. Pedal bike and check that chain is not rubbing cage as chainrings turn.

    1. If there is no gap and chain is rubbing cage, loosen L-limit screw 1/8 turn (counter-clockwise). Inspect for gap again and repeat until slight gap appears. 2. If the gap appears larger than 1mm at its widest point, tighten the L-screw, in small increments, until the gap closes.

5. Test the shift by shifting chain to next chainring then shift back to the innermost ring. Do not use the shift lever. Pull on the inner wire to shift the derailleur. Using the lever may confuse limit screw issues with cable tension issues. If chain shifts quickly, limit screw setting is adequate.
6. If the shifting appears is slow (requires more than one pedal revolution to initiate shift), turn L-limit counter-clockwise 1/8 turn and repeat test. Repeat 1/8-turn increments until shifting is adequate. The gap will open wider than the 1mm target, but will still be as small as possible with adequate shifting.
7. If chain is shifting beyond the inner ring and falls off the chainring, gap may be too large or cage alignment may be off. Tighten L-screw 1/8 turn and check shift again. If chain ends up rubbing inner cage of derailleur, yet still drops off inner ring when shifting, other problems such as chain line or derailleur rotation exist.

Front Derailleur- Adjusting H-screw

1. Shift to outermost sprocket in rear and outermost front chainring. Inspect derailleur for mark indicating H-screw.
2. Pull inner wire with hand to increase tension to insure derailleur is against H-screw.
3. Maintain full pressure on inner wire and check gap between chain and outer cage plate. Only a small gap should be visible, about 1/16" or 1mm. Pedal bike slowly and continue to sight gap. Set clearance at tightest point in chainring rotation.

    A. If chain is rubbing cage, loosen H-screw 1/8 turn and pull fully on inner wire. Check gap again. B. If chain is not rubbing, tighten H-screw repeatedly until chain is 1mm

4. Test shift to the large ring. Shift derailleur from next to largest to largest ring using hand pressure on inner wire rather than shift lever. If shifting is slow, loosen H-limit screw slightly and repeat test. If chain shifts off the outside of the large chainring, the outer-limit is set too loose. Tighten H-screw limit and test shift again.

Front Derailleur- Adjusting Indexing (Three Chainring Bikes)

1. Shift chain to middle chainring in the front and innermost rear sprocket.
2. View gap between inner cage plate and chain. Gap should be as small as possible without rubbing chain.
   
3. To reduce gap, increase inner wire tension by turning barrel adjuster counter-clockwise. Adjusting barrel may be on frame or on shift lever. Check gap again.
4. If chain is rubbing cage, turn barrel adjuster clockwise, or inward toward shifter body.
5. If barrel adjuster is all the way in or out there will be no adjustment possible. In these cases reset the barrel.   Shift to innermost chainring and loosen inner wire pinch bolt. Turn the barrel fully clockwise and back out about 2 full turns. Pull wire gently with fourth-hand tool and tighten pinch bolt. Begin adjustment of inner wire tension as above.
   
6. Test shift of front derailleur to all three front chain rings. If the derailleur rubs in the largest front chainring, double check H-limit screw and inner wire tension, which may be too loose. If chain is slow to shift to smallest chainring, double check L-limit screw and inner wire tension, which may be too tight.

Front Derailleur- Adjusting Indexing (Two Chainring Bikes)

1. Shift chain to outer chain ring in the front and outermost rear cog.
2. View gap between outer cage plate and chain.
3. If outer cage plate clears chain, index setting is adequate.
4. If plate is rubbing chain, increase inner wire tension by turning adjusting barrel counter-clockwise and check again.
5. If barrel adjuster is all the way in or out there will be no adjustment possible. In these cases reset the barrel.   Shift to innermost chainring and loosen inner wire pinch bolt. Turn the barrel fully clockwise and back out about 2 full turns. Pull wire gently with fourth-hand tool and tighten pinch bolt. Begin adjustment of inner wire tension as above.
6. Test shift of front derailleur to both front chainrings.

Front Derailleur Performance

• Repair Stand, PRS and PCS stands.
• Screwdriver, Phillips #2 or straight blade
• Hex Wrenches, if changing inner-wire AWS series.
• Light lubricant such as CL-1
• Forth Hand Tool BT-2
• Cable cutter, if trimming cable CN-10
• Rags

• Front derailleur- limits screws and index settings
• Wire cable-sizing and cutting inner wire cable and housing (gear and brake)
• Brake and Shift levers
• Rear derailleur- overhaul
• Rear derailleur- bent hanger

Derailleur Limit Screws (H-Screw and L-Screw)

H-Limit Screw

• Shift chain to outermost (largest) chainring. Shift chain to outermost rear sprocket (smallest sprocket).
• Check tension on rear inner wire. If inner wire appears to have any tension, it may interfere with the H-screw setting. Turn adjusting-barrel clockwise to eliminate inner wire tension. Proper cable tension (indexing) will be adjusted later.
• Pedal bike at a quick cadence, approximately 60 rpm or more.
• Pull inner wire to shift derailleur one sprocket inward. Adjust pull on inner wire until chain rides quietly on second sprocket. Release inner wire quickly to shift back to outermost sprocket and note shift. When adjusting the H-screw, be concerned with two situations:
  1. The outward shift from the second sprocket to the outermost sprocket.
  2. How the chain rides on the outermost sprocket.
  3. Do not be concerned with how the chain rides when it is held on the second sprocket.
  4. If the shift outward seems acceptable, tighten H-screw 1/4 turn clockwise and repeat shift. Even if shift appears acceptable, continue tightening H-screw by 1/4 turn increments and checking shift until shifting is slow or hesitant. Another symptom of a too tight H-limit screw is when the chain is on the smallest cog but makes a rattle from rubbing the second sprocket inward. View this last symptom by looking under the rear sprockets where the chain meets the sprockets. The inner plate of the chain will rub against the next sprocket inward making the noise.
  
  5. When symptoms of a too tight H-screw appear, loosen H-screw 1/4 turn and check shift again. Repeat process of shifting and correcting by 1/4 turn increments. When too tight symptoms disappear, H-screw is at tightest acceptable setting, and limit screw setting is done.
  NOTE: "Rapid Rise" or "Low-Normal" derailleurs use a reverse spring application. When the inner wire tension is completely relaxed, the derailleur sits on the inner most sprocket, which is reversed from other common derailleurs. When adjusting the H-limit screw, it is necessary to pull the inner wire until the chain is in the second to outermost sprocket then pull hard to shift to the outermost sprocket. The same concept is used to adjust the Shimano® "Rapid-Rise" or "Low-Normal" derailleurs. You want the tightest limit screw setting that allows good shifting to the extreme outer and inner cogs.

  L-Limit Screw

  The L-limit stops the derailleur from moving inward (toward the spokes). The limit screw does not make the derailleur move, pulling the inner wire makes the derailleur move. The L-screw allows the pulley wheels to shift the chain to the innermost sprocket and yet not shift off the sprocket into the spokes.
  1. Shift bike to middle chainring (or smaller ring of double chainring bikes) and to second-to-innermost rear sprocket.
  2. Pedal bike at a quick cadence, approximately 60 rpm or more.
  3. Pull inner wire by hand to shift derailleur sprocket inward. When adjusting the L-screw, be concerned with two situations:
     1. The inward shift from the second-to-innermost sprocket to the innermost sprocket.
     2. How the chain rides on the innermost sprocket.
     3. If shifting seems adequate, tighten L-screw 1/4 turn, and repeat shift. Continue to tighten L-screw until symptoms of too tight appear. These symptoms are that the chain will not complete shift even with pressure on inner wire, the chain hesitates before shifting inward even with constant pressure on inner wire, or the chain rattles excessively when riding on innermost sprocket
        
     4. When symptoms of a too tight L-screw appear, loosen L-screw 1/4 turn and check shift again. Repeat process of shifting and correcting by 1/4 turns. When too tight symptoms disappear, L-screw is at tightest acceptable setting, and limit screw setting is done.

     B-Screw Adjustment

     After setting the L-screw, check the "B-screw" for an adequate setting. The B-screw controls the derailleur body angle, hence the name, B-screw. Shift to the innermost rear cog, which is the largest cog. View the upper pulley relative to the largest cog. If the pulley is rubbing against this cog, tighten the B-screw to increase upper pivot spring tension, which pulls the pulley back and away from the cog. If there is a large gap between the upper pulley and cog, loosen the screw. To find a good setting, loosen the B-screw until the upper pulley begins to rub, then tighten the screw to get clearance.
     
     
     Check for rubbing of largest sprocket and upper pulley
     
     
     Change B-screw as necessary
     
     
     Campagnolo® Some Campagnolo® model derailleurs have a body tension adjustment at the pulley cage, not at the upper pivot. The screw is basically a "rack and pinonquot; system. The cage spring plate rotates to increase or decrease tension. The upper pivot and lower cage pivot springs oppose one another. In this system, the upper spring is fixed. Increasing cage tension (turning screw clockwise) will bring the upper pulley closer to the cog. Decreasing cage tension (turning screw counter-clockwise) will increase the distane between upper pulley and cog.
     
     
     
     SRAM® Derailleurs Sram® designates a 6mm between the largest rear cog and the upper pulley. Use a 6mm hex wrench to help estimate this gap.
     NOTE: Shimano "Rapid rise" or "Low-Normal" Shimano® reverse the spring pull from conventional derailleurs. The derailleur moves inward (toward the spokes) when the cable tension in relaxed, or or "normal" position. To adjust L-screw, pull on inner wire and shift outward one sprocket, then release inner wire to shift inward. Tighten L-screw until shifting is slow, then turn counter-clockwise 1/4 turn until good shifting is restored.
     
     
     The process above sets the limits to the tightest setting that still shifts well. This allows the derailleur to wear with use and time, and yet still allow a good setting. After limit screws are set, proceed to index adjustments.

     Checking the Rear Indexing Adjustment

     The rear indexing adjustment should only be done after the H-limit and L-limit screws are adjusted. The rear derailleur indexing is adjusted by changing the inner wire tension. For the common rear derailleurs, increasing inner wire tension tends to move the rear derailleur more to the left, or toward the spokes. Less inner wire tension tends to move the derailleur to the right. The inner wire tension will not stop the derailleur at its extreme limits. The H-limit screw stops the derailleur at its right most setting, and the L-limit screw stops the derailleur at its left most setting. (Shimano® "Rapid rise" or "Low-Normal" derailleur are a bit different. These place the chain under the inner most sprocket when there is no cable tension. See procedures at the bottom of article.)
     Modern indexing shift levers use dwell, which is a hesitation between movements in the lever. These hesitations are timed to match the movements of the derailleur and the spacing in the rear sprockets. The design of some derailleur and shift lever brands requires more of a push (or twist) of the lever to complete the shift. The amount of extra push or twist is not consistent between manufacturers and each rider must learn the particular attributes of his or her system.
     Changes to inner wire tension are made at the adjusting barrel. Adjusting barrels may be located either at the rear derailleur or at the shift lever. The goal of adjusting the indexing is to find the tightest inner wire tension setting that will allow good shifting to the gears normally used. This will allow the longest lasting indexing adjustment as the system wears and the cable system stretches with use. To find the tightest inner wire setting, you will purposely make the setting too tight then relax tension slightly. There are two basic symptoms for a "too tight" inner wire. These are a rattling noise from the chain rubbing against the next cog inward, and a slow or hesitant outward shift. These are symptoms for rear derailleurs that sit outward when inner wire tension is released.
     NOTE: If the cable inner wire is not correctly routed into the derailleur pinch bolt, a good indexing setting may not be possible. The wire should leave the barrel adjuster and travel straight to the pinch mechanism. The upper image is correctly routed, while the lower image shows incorrect routing.
     

     Index Setting

     1. Set limit screws (if not already done).
     2. Shift chain to outermost rear sprocket (smallest). Shift chain to outermost (largest) chainring in front.
     3. Test initial inner wire tension. Pedal a normal cadence and shift rear derailleur with one click on lever. Use care to only move lever one position. If derailleur moves one sprocket, tension is adequate.
     4. If derailleur fails to shift one sprocket, inner wire may be too slack. Turn barrel adjuster fully into derailleur body (or shift lever) then turn counter clockwise two turns to allow for index adjustments. Loosen inner wire pinch bolt and gently pull on inner wire with fourth hand tool or pliers to remove slack. Tighten inner wire pinch bolt.
     5. If derailleur will not shift one sprocket after removing slack in "d", return lever back to outermost sprocket position and increase inner wire tension by turning barrel adjuster counter-clockwise 1/4 turn and attempt shift again.
     6. Shift to second sprocket in rear. Pedal and increase inner wire tension by continuing to turn adjusting barrel counter-clockwise until a definite rattling is heard. Rattle is from chain scrapping against next sprocket.
     7. Once a too-tight rattle is achieved, turn barrel adjuster 1/4 turn clockwise, to release inner wire tension, and pedal again. Listen and look for signs of scraping or rattling. Continue turning barrel adjuster 1/4 turn clockwise at a time until rattle disappears.
     8. Shift derailleur one sprocket inward at a time, listening for signs of rattle, indicating a too tight inner wire. Turn adjusting barrel 1/4 turn clockwise to eliminate rattle. Note: Do not attempt shift to largest rear sprocket while in largest front sprocket. This gear is normally not used and adjusting tension to this shift may compromise other commonly used gears.
     9. Shift to innermost (smallest) chainring and check gears again. If no rattling is present, index adjustment is done.

     Shimano "Rapid Rise" or "Low-Normal" Derailleur Indexing Adjustment

     Shimano "rapid rise" or "Low-Normal" derailleurs use a return spring that puts the derailleur under the innermost rear sprocket when the inner wire tension is released. As with other indexing derailleurs, the inner wire tension should be set as tight as possible with good shifting. However, the symptoms of a too-tight setting are different, which for "Low-Normal" systems are when the derailleur shifts outward slowly, or a there is a rattle from the upper pulley being aligned too far outward. Look underneath the rear sprocket at the alignment of the upper pulley when there is a rattle to see if this is the cause.
     1. Shift chain to middle ring in front and innermost sprocket in back.
     2. Pedal and shift lever one position.
     3. Pedal and turn barrel adjuster counter-clockwise to tighten inner wire tension until chain begins to shift outward.
     4. Turn barrel adjuster clockwise 1/4 turn until chain runs smoothly on second cog.
     5. Shift outward one sprocket at a time trying each gear. Turn barrel adjuster 1/4 turn clockwise if too tight symptoms occur.
     6. Shift to all other normal gear combinations and test adjustment.
     NOTE: The indexing procedure here assumes that there are no unusual problems, such as bent derailleurs, bent derailleur hangers or excess inner wire friction from dirt in the housing. Additionally, manufacturers design shift levers and drive train components to work within their system. Mixing brands within the drive train may lead to poor shifting. This is referred to as an compatibility problem.