STI, or System Total Integration, is Shimano's line of road bike gear shifters. The shifter integrates shifting and braking functions into one control. The shifters come as a pair and are mounted to either end of the handlebar, with one shifter controlling rear braking and shifting functions and the other shifter controlling the same functions at the front of the bike. Shifting function precision relies chiefly on tension from the attached cable. The cable connects the STI shifter to a derailleur. The derailleur is directly responsible for shifting the chain between gears. The cable is adjusted to reverse sluggish shifting.
Use the rear Shimano STI shifter to shift the chain to the outermost rear sprocket. Shifting is performed while riding the bike or by briefly raising the rear wheel, shifting the gear and rotating the pedals forward.
Follow the cable from the Shimano STI shifter to the rear derailleur. The cable ends at the derailleur.
Locate the adjusting nut at the back of the derailleur. The cable passes through the nut just before entering the derailleur.
Turn the nut counterclockwise to add tension to the STI shifter cable. One to two turns will suffice for now.
Use the STI shifter to shift the chain to the next sprocket over. Again elevate the rear wheel and turn the pedals forward.
Continue to shift through the rear gears. If the chain stalls at any point, and fails to shift to the next sprocket, add further tension to the cable, by turn the adjusting nut counterclockwise as needed.
Use the front Shimano STI shifter to shift to the innermost front chain ring. As before, the pedals and crank must then be rotated forward to complete the shift.
Locate the adjusting nut, midway along the cable that connects the front STI shifter to its derailleur.
Turn the nut counterclockwise to tighten the shifter cable. Begin with one to two turns.
Shift to the large chain ring. Lift the rear of the bicycle and rotate the crank forward.
Add further tension to the cable as needed or until the chain transfers efficiently to the larger gear.