Broken shifters can make a bicycle ride more difficult than it has to be. Broken gear levers often need to be replaced, but first determine if this is the step you need to take. Often, a malfunctioning shifter is the result of other problems on your bicycle. Worn cables and cable housings are the most likely culprit, while a thorough cleaning of the shifter assembly also might correct the problem.
Loosen the pinch bolt on your derailleur with an Allen wrench. The pinch bolt is on the opposite side of the shifter cable from the handlebars and secures the end of the cable to the derailleur. Remove your cable from the pinch bolt and the cable housings, which are the tubes the cable runs through between the shifter and the derailleur.
Remove the cable cap on your shifter using a screwdriver; the cable cap is a plastic screw generally found on the front of the shifter. Push your cable through the shifter until the head of the cable is visible. Pull your cable through your shifter.
Check your cable for bends or kinks. Replace your cable if it is frayed, worn or bent. Check your cable housings for bends or kinks. Replace them if they are damaged.
Remove the nut holding the break assembly from your handlebars using a crescent wrench or ratchet set. Slide the brake assembly off your handlebars. Take the bolt holding your shifter off your handlebars using a crescent wrench or ratchet set. Slide the shifter off the handlebars.
Remove the barrel adjuster, which is where the cable protruded from the shifter, by unscrewing it by hand. Remove any cover plates, which are plastic guards, from the shifter assembly using a screwdriver.
Spray your shifter assembly thoroughly with WD-40. Wipe the shifter assembly with a clean rag and allow it to dry.
Apply spray grease to any moving parts of your shifter. Reassemble the shifter. Shift your shifter through all of the gears to allow the grease to penetrate all moving parts.
Reinstall the shifter onto your handlebars. Reinstall the cable through the shifter, cable housings and the pinch bolt on your derailleur. Position your shifter in the lowest gear. Tighten the pinch bolt with an Allen wrench.
Test your shifters to make sure the gears shift properly. Replace your shifters if they still do not work properly.