Geared bicycles generally contain a set of gears at both the rear and front of the bicycle. Both sets rely on a mechanism called a derailleur to shift the chain between the individual gears. The derailleur is linked by way of a cable to a hand-operated shifter. For front gears, the shifter is located on the left side of the handlebar. When the cable linking the shifter to the derailleur is loose, the derailleur will struggle to shift the chain to a larger gear. If the cable is overly tight, the shifter may be difficult or impossible to operate. Optimal cable tension allows the cyclist utilise all gears.
Locate the adjusting barrel. Road bike adjusting barrels are found midway along the cable attached to the bicycle frame. Mountain bike adjusting barrels are placed directly beside the gear shifter hand control.
Determine whether the cable needs to be tightened or loosened. If the chain is failing to shift to a larger front gear, the cable needs to be tightened. If the chain shift to a larger gear but requires excessive force to shift, the cable may be too tight.
Turn the barrel in the required direction. Turning the barrel counterclockwise tightens the cable. Turning the barrel clockwise loosens the cable.
Shift through each of the front gears to check the adjustment. Check for improvements in shifting performance. Continue to adjust the gear cable, using the adjusting barrel, if necessary.