23. How to Replace Your Chainrings
Basic removal and installation instructions for 5-bolt chainrings on 3-sprocket systems.
This tutorial will demonstrate how to remove and install chainrings. Since there are so many different crank and chainring sizing combinations, I'll stick to the basics and give a general overview of the process based on a 5-bolt, 3-chainring system.
Before removing the largest two chainrings you'll often have to remove the smallest one, which is often threaded directly into your crank arm. Use your allen key to loosen all of the bolts that hold the chainring in place, and then use a marker to make a note of the chainring's position in relation to the crank before removing it completely. Some chainrings have a bump sticking out that should be lined up with your crank arm.
The largest two rings are usually bolted to each other with a nut and bolt. Here you'll need to hold the nut in place with the special chainring wrench while you loosen the bolt with your allen key. Once again it's a good idea to mark the chainring's position in relation to your crank arm. The two largest outer rings often have a few spacers or washers in between, so be sure to note exactly how they came apart so they can be reinstalled correctly.
While it's ok to install a new chainring that has a different number of teeth, you'll want to make sure that your new chainrings have the same side profile as the old ones.
Before you reinstall the bolts, apply a thin layer of grease to the threads to keep out moisture. Now you can reassemble all of your chainrings the same way they came apart.
Make sure all of the bolts are finger tight and then begin tightening them evenly in a star pattern. Start by tightening the first bolt, and then every second bolt until you've gone all the way around. Repeat this process until all of the bolts are tight. Be careful not to over-tighten. Park Tools recommends 44-88 inch pounds of torque for aluminum bolts, and 70-95 inch pounds for steel bolts.