Chainrings serve as gearing for bicycles. Differing in size depending on the desired gearing, chainrings attach to the bicycle crank and are rotated by the turning pedals. A typical Shimano crank may use as many as three chainrings or just one. The chainrings are fastened to the crank and to one another by a series of bolts. Chainrings can be swapped for different sizes or replaced if worn.
Choose any one of the 5 chainring bolts to remove first. The bolts are spaced along the diameter of the outer chainring.
Fit a flathead screwdriver against the back of the first chainring bolt. The back of the chainring bolt has a narrow slot for the screwdriver.
Fit a 5mm Allen key into the head of the chainring bolt. While holding the chainring nut in place with the screwdriver turn the Allen key counter-clockwise to loosen the bolt.
Unscrew the chainring bolt fully from the nut.
Follow Steps 2 through 4 for the other bolts.
Separate the Shimano chainrings from the bicycle crank.
Fit the new Shimano chainrings, aligning the holes in the chain ring and the crank. If you're replacing all the chainrings, place them in order so the smallest chainring goes on first.
Grease the threads of each chainring bolt.
Fit one of the nuts through the back of the Shimano chainring. Hold the nut in place using the flathead screwdriver.
Thread a chainring bolt through the hole in the chainring and onto the nut. While continuing to hold the nut in place with the screwdriver, turn the bolt clockwise with the 5mm Allen key to tighten.
Install the other four chainring bolts, following Steps 3 through 5.