Fitting a chain ring to your bike is a relatively simple task, but you will need to ensure that you get the correct size for your crank. There are a number of standards out there for what is known as the Pitch Circle Diameter (PCD) of the mounting bolts. Campagnolo, for example, uses 112mm and 145mm, while Shimano uses a universal 110mm – so make sure you get the right one!
How to replace a bicycle chainring
Time take: 20 minutes
Mobey saved: £10
What you'll need: 4MM allen key, grease, torque wrench
Step 1 - Remove the chainset
Once you’ve removed the chainset (Read our guide on how to do that here) locate the chainring bolts on the crank. These are usually fitted using a 4mm Allen key and should be screwed on very tightly – so don’t be surprised if you can’t undo them with a simple flick of the wrist. Elbow grease will be required!
Step 2 - Loosen the bolts
Using the 4mm Allen key, simply undo the bolts by turning them in a counterclockwise direction. If any are really stuck, give them a quick blast of silicone spray like Finish Line’s Pedal and Cleat Dry Film lubricant to loosen them up.
Step 3 - Remove the rings
Once you’ve removed the bolts and put them to one side, remove the chainrings for cleaning or replace them with new ones. You can tell if a chainring needs replacing by the profile of the teeth – if they are pointed like shark’s fins, it needs replacing.
If you are cleaning it, spray with a dedicated cleaner, leave it for a minute to soak in then scrub down with a stiff brush.
Step 4 - Clean and grease the bolts
Use degreaser to clean the bolts. Before reinserting them, give them a quick coat of decent-quality fresh grease and apply some to the boltholes, too.
This will not only prevent the bolts from seizing up but will also stop them from drying out – leaving your bike less susceptible to creaking and squeaking. It’ll also mean they’re easier to remove next time you do this job.
Step 5 - Inspect the chainring
Examine the chainring for an alignment arrow, which indicates where it needs to line up with the crank. Otherwise, use the chain pip as a guide – this is the small grommet that’s designed to stop the chain getting stuck if it comes off the big ring.
This will need to be mounted behind the crank.
Step 6 - Put it all back together
Finally, screw the bolts back in and – using a torque wrench – check you have tightened them up sufficiently by listening out for the torque wrench to click.
Loose chainring bolts can create annoying clicking noises around the bottom bracket and – over time – can work themselves free. Which is not good!