How to Adjust Rear Bicycle Gear Indexing

Place the bicycle in a stable repair stand with its rear wheel off the ground. Keep hands, sleeves and loose items away from the moving chain and spokes. Locate the ridged barrel adjuster where the gear cable enters the rear derailleur or the rear shifter. Take a photo of its starting position so you can reverse changes. Wipe away surface dirt around the adjuster with a clean cloth. Do not loosen the cable anchor bolt.

Pedal slowly by hand using the crank, not by pulling the chain. Shift one click at a time between two middle rear sprockets. Observe whether the chain hesitates when moving to a larger sprocket (easier gear) or to a smaller sprocket (harder gear). Make only one type of correction at a time. If the chain jumps unexpectedly, rubs the spokes, or shifts past the cassette, stop: indexing alone may not be the problem.

If the chain is reluctant to move inward to the next larger rear sprocket, add a little cable tension. Turn the barrel adjuster counterclockwise by about one quarter turn, as viewed looking directly at the adjuster from the cable-entry side. Pedal slowly and repeat the same one-click shift. Make another small correction only if necessary. If the shift becomes worse or the adjuster is almost unscrewed, return toward the starting position and stop.

If the chain is reluctant to move outward to the next smaller rear sprocket, reduce cable tension instead. Turn the barrel adjuster clockwise about one quarter turn, viewed from the same cable-entry side. Turn the cranks slowly and repeat the same one-click shift. Do not make large turns or force the shifter. If symptoms alternate unpredictably, suspect a sticky cable, worn chain, or alignment problem and seek a mechanic.

With the bicycle still secured, shift through the full rear gear range one click at a time while pedalling gently. Shifts should settle promptly on each sprocket without rattling or trying to enter the spokes. Return to a middle gear and confirm both directions again. Avoid extreme front-to-rear chain angles. If the chain overshoots an end sprocket, the derailleur appears tilted, or noise persists, stop and have the gear system inspected; do not try to correct it with limit screws here.

After confirming the rear wheel is secure and the stand is removed, take a short test ride in a quiet traffic-free area with a helmet. Shift one rear gear at a time under light pedalling pressure; ease off force as the chain changes sprockets. If shifting is smooth in the stand but skips under load, or if grinding, unwanted shifts or chain drops occur, stop riding and arrange a professional inspection. Record the final adjuster position for future reference.