Rear Derailleur Adjustment

1. Pre-Adjustment Check

Visually check that the rear derailleur cable housing has no kinks, and that any bends in the housing are smooth and not too sharp. Turn the handle bars to one extreme then the other to check that the housing is not pulled too tight.

Visually check the rear derailleur cable housing at the rear derailleur, once again checking for kinks and adequate length.

Inspect the cassette for missing or bent teeth. Also make sure that the cassette spins freely.

Visually check the rear derailleur hanger for damage. Looking at the hanger from the behind the bike, it should be straight, not bent toward or away from the wheel.

Inspect the chain for bent links, missing rollers, or other damage.

Check the rear derailleur cable for a frayed end.

If the end is frayed only part way to the cable anchor, it is possible that you could cut off the excess cable up to where it starts fraying, and clamp on the appropriate end cap.

Make sure that the cable anchor plate is in the correct orientation. Many cable anchor plates have a groove for the cable to sit in.

Make sure that the rear derailleur mounting bolt is tight.

Make sure that the guide pulley, and tension pulley mounting bolts are tight.

2. Adjusting the rear derailleur

Shift into the highest rear gear. (Physically smallest cog).

Make sure that the rear wheel is seated flush in the dropouts.

At this point, from the rear of the bike, visually check the cageplates of the rear derailleur. They should be parallel to the gears.

If the derailleur is not lined up, figure out which part of the system is bent or misaligned.

If the derailleur hanger is bent, depending upon the frame material, it may be possible to bend it back into shape.

The frame shown in the picture has a replaceable rear derailleur hanger.

If it is bent, the derailleur hanger can be unbolted from the frame, and replaced with a new one.

If some part of the derailleur is badly bent, you may have to replace the derailleur.

Turn the rear derailleur barrel adjuster clockwise all the way, then unscrew it one full turn.

Turn the rear shifter barrel adjuster clockwise all the way, then unscrew one full turn.

Loosen the rear derailleur cable anchor nut with the appropriate tool.

This leaves the rear derailleur in its fully retracted, unactivated position.

Typical rear derailleurs retract to the highest gear (smallest cog) position when unactivated.

(Some rear derailleurs retract to the lowest gear position; set up procedures will need to accomodate the style of derailleur at hand.)

The rear derailleur cable should now be slack. Pull on the cable to feel if it is tight or loose.

Set High Gear Limit Screw

Locate the screw marked by "H" on the rear derailleur body.

On some derailleurs, there will be no marking, in which case you can try turning one screw and then the other while watching the rear derailleur from behind. The rear derailleur should move toward the wheel when you turn one of the screws clockwise. This screw is the high gear limit screw.

Use this screw to line up the guide pulley on the rear derailleur with the smallest cog on the cassette.

Turning the screw clockwise moves the derailleur to the left, toward the wheel.

Turning the screw counterclockwise moves the derailleur to the right, away from the wheel.

Re-Anchor Rear Derailleur Cable

Pull the rear derailleur cable tight by hand and tighten the cable anchor nut with the appropriate wrench.

Set Low Gear Limit Screw

Shift the chain onto the lowest gear (physically largest rear cog).

Without turning the pedals, operate the rear shifter and shift up one gear.

This loosens the rear derailleur cable.

By hand, push the rear derailleur body to the left until it stops, then hold it there.

Identify the low gear limit screw. It is usually marked by an "L" on the derailleur body. If there is no marking, then it is the screw right next to the high gear limit screw that you identified earlier.

Now, turn the low gear limit screw to adjust it so that the largest cog, chain and guide pulley are all lined up.

Turn the low gear limit screw clockwise to move the derailleur to the right.

Turn the low gear limit screw counterclockwise to move the derailleur to the left.

Spin wheel in reverse to watch the chain move through the gears.

Visually verify alignment as shown.

Adjusting B-Tension Screw

The B-Tension screw determines how close to the rear cogs the guide pulley of the derailleur is.

Turning the B-Tension screw clockwise moves the guide pulley away from the cogs.

The optimum setting for the B-Tension screw will bring the guide pulley as close as possible to the lowest gear without the guide pulley smashing the chain into that gear.

With the front derailleur shifted to the lowest gear, and the rear derailleur shifted to the lowest gear, turn the pedals backwards and watch the low gear/chain/guide pulley interface.

If the guide pulley is too far away from the largest cog, then turn the B-Tension screw counterclockwise.

If it is too close to the largest cog, then turn the B-Tension screw clockwise.

Fine Tuning Rear Derailleur Cable Tension

Shift the rear derailleur to the middle gear.

Spin the wheel backwards and observe the chain and guide pulley alignment.

Turn the rear derailleur barrel adjuster until the guide pulley, chain and middle gear all form a straight line.

Turning the barrel adjuster clockwise moves the guide pulley to the right.

Turning the barrel adjuster counterclockwise moves the guide pulley to the left.

Final Run Through

While turning the pedals forward, repeatedly shift from the highest gear to the lowest gear and vice versa. Watch and listen to the shifting action. Make sure that the chain does not fall off the high or low gear.

If the chain falls off the high or low gear, you need to adjust the corresponding limit screw.

Shift between each gear combination one at a time and watch the shifting action. If the shifting action is slow in one direction, use the barrel adjuster on the rear derailleur to fine tune the position of the rear derailleur.

If it is slow shifting to higher gears, you will need to turn the barrel adjuster clockwise.

If it is slow shifting to lower gears, you will need to turn the barrel adjuster counterclockwise.

Once you have finished adjusting the rear derailleur in the repair stand, test ride the bike and shift through all the gears while pedaling.

If necessary, make adjustments to the limit screws or the cable tension to improve shifting.