Buying Bicycle Cranksets and Chainrings: What You Need To Know

autorRotor Bike Components
fecha9th May 2018

Whether you are upgrading or simply replacing worn out components, when it comes time to buy new cranksets or chainrings, there are several key parameters to consider. Here’s what you need to know to help you select the correct new components.

Chainrings, Crankset or Both?

First, you need to determine whether you’ll be changing only your bicycle chainring(s), your crankset or both. Most bicycle cranksets are designed with replaceable chainrings, so you can easily and more affordably swap the rings without having to replace your entire crankset. If your crankset is still in good shape, you may only have to swap your chainrings the next time you do your drivetrain maintenance. Quality cranksets last for years and many sets of chainrings.

Number of Chainrings

Cranksets commonly come with one, two or three chainrings, depending on your bike’s age and intended use. The trend over time as we get more and more gears out back is to have fewer chainrings up front. A majority of modern road, mountain, gravel and cyclo-cross bikes now come with just one or two chainrings. The advantage to having just one chainring is that your bike will not need a front derailleur or shifter, which means it will be lighter and cleaner-looking with fewer parts and cables. The disadvantage, of course, is fewer total gear choices.

Size of Chainrings

No matter how many chainrings you have, size does still matter. If you’re swapping out chainrings, be sure to check how many teeth are on each and replace your existing rings with a chainrings that have the same number of teeth, unless you are intentionally trying to alter your gearing. Chainrings with more teeth feel harder to pedal and chainrings with less teeth feel easier to pedal.

Shape of Chainrings

Traditional chainrings were circular, but many new chainrings are oval shaped. Oval chainrings such as ROTOR’s Q RINGS have been shown to not only reduce stress on the knees but also to improve performance and thus minimize fatigue. Q RINGS virtually decrease the gear ratio in the dead spot of your pedal stroke and increase the gear ratio in the power phase, which is when you exert the most force while pedalling. They are also adjustable, with up to five different positions, to suit your unique pedaling style. If you are switching from round to oval chainrings or vice versa, you will typically also have to purchase new cranks that will fit the different style of rings.

Method of Attaching Chainrings

It’s not just about how many teeth your chainring has. There are many different crankset designs out there, which means there are many different ways of interfacing with chainrings. Chainring bolts are the most common way of attaching chainrings: typically using four or five such bolts. It’s also important to know the exact pattern of those bolts – factors such as bolt circle diameter (diameter of the circle that connects the center of all chainring bolts) are important in spec’ing a chainring that will fit on your cranks. Many chainrings are not compatible across different brands or even across different models for any given brand.

Method of Attaching Cranksets

Cranksets attach to a frame via bottom bracket, and there are many different types of bottom brackets. If you’re swapping out your entire crankset, be sure to select one that is compatible with your current bottom bracket type. Special tools are required to remove and install a majority of types of bottom brackets and cranks, so if you’re confused about what kind of bottom bracket you have, what tools you’ll need to swap cranks or how to use those tools properly, consult your local bike shop for help.

Crank Length

Cranks come in a range of sizes, most commonly from 165mm to 190mm, and ideal crank length is often determined by three factors: your height, your cycling discipline and your personal preferences. If you change your crank length, it will change how it feels to pedal your bike, and it may change your fit on your bike. When replacing your cranks, check to make sure you’re swapping them out for the same size unless you’re intentionally trying to make them longer or shorter.

Read more:

Why so many different cranks and which suits you best?

Single or double chainrings: which is better for mountain biking?

Converting from single to double chainrings: What you need to know

Wellness benefits of Q chainrings