Shimano shifters are known for their shift accuracy, dependability and long-term strength. They are some of the most popular bicycle shifters on the market today for these, and many more, reasons. However, the shifters will only work properly if they are set up and adjusted correctly. If not, the bicycle will shift erratically, sometimes missing shifts entirely and other times shifting too many gears at one time. Smooth out your ride by adjusting your Shimano shifters at home.
Set the bicycle in a work stand if you have one available, as this will allow you to spin the wheels while you work. If you do not have a work stand, set the bike on its kickstand while you work.
Use a combination or hex wrench to loosen the cable stop bolt on both the front and rear derailleurs. Tighten the barrel adjuster on each shifter toward the shifter body by turning the adjusters clockwise with your fingers.
Use your needle-nose pliers to pull the front derailleur cable taut under the cable stop. Tighten the cable stop so that the cable does not have any excess play.
Hold the cable of the rear derailleur taut under the cable stop using your needle-nose pliers. Tighten the rear derailleur cable stop so that cable has no excess play.
Spin the cranks of the bicycle forward in the work stand, or take the bike for a test ride. Shift through every gear on both the left and right shifters feeling carefully for missed- or over-shifts. If either shifter is too tight, and shifts more than one gear at a time, loosen the cable under the cable stop slightly. If either shifter is too loose, and misses shifts or doesn't shift at all, turn the barrel adjuster on the shifter counter-clockwise to tighten the cable.