Index A Bike’s Rear Derailleur
A friction rear derailer is set-up once the limit screws are set and the cable connected. An indexed system, where the shifters click between gear positions needs to be tuned or indexed. the process of indexing is getting the hand control and the derailleur mechanism in tune with each other. Connect the cable with the derailleur in top gear, give the shifter one click. If this makes the derailleur shift one gear the cable was tight enough. If it doesn't make the derailleur shift adjust the cable until the derailleur is in a position that matches the position selected by the shifter.
Set The Shifter
Select the highest gear on the rear derailleur with the shifter and connect the cable. If the cable is already connected screw down all the barrel adjusters. if this leaves the cable very slack unlock the cable and pull the slack through.
Tighten The Cable
If the gear didn’t shift in response to the first click screw the barrel adjuster on the rear derailleur anti-clockwise to tighten the cable until the derailleur shifts into the second highest gear x-1.
Check The First Interval
Check the top jockey wheel is sitting directly under the second smallest cog. Make fine adjustments screwing the barrel adjuster anti-clockwise to move the chain left, clockwise to move it right. Turn the pedals backwards to check the chain is running smoothly on the cog for the second highest gear.
Check The Downshifts
Click the shifter one step at a time going down through the gears onto bigger cogs.
Check The Upshifts
Click the shifter one step at a time going up through the gears onto smaller cogs.
Fine Adjustments to the rear derailleur
If the chain is reluctant to shift onto a smaller cog loosen the cable by screwing the barrel adjuster clockwise.
Shift gear one click without pedalling, then turn the pedals. The gear should shift as soon as you pedal. In use the rider will pedal as they shift so if the system works with this delayed pedalling it’s a good indication that the cable tension is correct.
If the rear derailleur works in the opposite direction. Use the same process but start in the lowest gear and set the first interval to second gear.