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The derailleur is a mechanism that shifts the chain from gear to gear in order to give multiple forward speeds. A lever on the right side of the frame tube operates the rear derailleur, usually over a cluster of five gears. To obtain 10 speeds, bikemakers combine this rear cluster with a two-gear chain wheel, controlled by a lever on the left side of the frame.
If you encounter binding or slippage as you shift, check the cables and replace any that are kinked, frayed, or broken. To remove the old cable, loosen its anchor bolt at the gear cluster and pull cable forward through the guides. Finally, adjust lever to attain proper cable tension.
After removing the old cable, set the gear lever at its halfway position and thread the entire length of new cable through the hole in the lever. Make sure that the nipple at the end of the cable is seated in its recess. Pull the lever back as far as it will go. Feed the cable back through the lever's guide eye and pull it tight. Feed the cable back through the guide channel just above the bottom bracket of the bike.
Pass the cable through the eye on the horizontal rear fork stay. Then, slip the short length of plastic outer casing over the cable end and push the casing forward until it rests against the eye.
Slide the cable through the cylindrical guide on the carrier mechanism. Pull the cable downward until the end of the outer casing touches the guide.
Move the gear lever all the way forward. Slip the cable between anchor bolt washer and the tip on the anchor bolt flange. Pull the cable taut and tighten the bolt. Push plastic protector sleeve (if supplied) up over the cable end until it rests against the anchor bolt. Snip off any surplus cable.
Test-ride the bike. If the gear lever is too loose, the chain will slip into high gear constantly. If it is too tight, the lever will be difficult to move. Adjust the center bolt of the lever for proper tension, if necessary.
You will want to keep the Derailleur tuned on your bicycle to prevent this repair in the future.
Derailleur systems slip out of adjustment more frequently than three-speed hub gears. You can avoid many problems by handling the bike with reasonable care. Limit the amount of off-pavement riding, which tends to loosen the delicate cages that transfer the chain from gear to gear. Shift gears while pedaling, not while coasting, and do not backpedal. Never lay the bike on its right side. If the shift lever binds, do not force it, inspect the system and make adjustments.
First check the cables and clean the sprockets and chain with a solvent-soaked cloth. If the chain is worn, replace it. There are two types of cage adjusters, double screw and single screw. Adjusting either type is a trial and error operation. Have a helper raise the rear wheel clear of the ground and shift gears while you turn the pedal by hand. The adjusting screws must be set so that the chain does not overshoot the sprockets and fall off when it is shifted. But it should not rub against the cage in any gear between shifts.
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