2025-07-20
All About Bicycle Chainrings: From Teeth to BCD
In the last article, we mentioned the use of chainrings and what part they play in the drivetrain. They are the crucial part that helps us transfer pedaling power to the chain. Chainrings differ depending on the bike's design and purpose. In this article, we are going to dig into different kinds of chainrings and how to choose a suitable chainring. Types of ChainringsRoad Bike ChainringRoad bikes are often equipped with two chainrings. One is standard chainrings. The other is compact chainrings. Standard Chainrings are built for speed. They’re great on flat roads and used by racers who want to go fast. As for compact chainrings, they are a bit smaller and make it easier to pedal. There are also road bikes that are equipped with only one chainring. Some pro road cyclists have started using them during flat races or roads with cobblestones.Road bike values smooth shifting performance. As a result, road bike chainrings are usually designed with lightweight materials. Mountain Bike ChainringMountain bikes often use only one single chainring. They are simple and the chain is less likely to come off. As for mountain bikes that use two chainrings. They are heavier and a bit more complicated to use, since you need to shift both front and back. But they can be more efficient, especially if you want a wider gear range for climbing steep hills.Mountain bikes usually opt for smaller chainrings for better control. Gravel Bike ChainringWhen setting up a gravel bike, choosing between one chainring and two chainrings really comes down to how and where you ride.If you’re mostly riding on paved roads and want more gear options to stay in your ideal cadence, then using two chainrings is a great choice.But if you spend more time on rough, technical gravel trails, and want something that’s simple, quiet, and less likely to drop the chain, then go with one chainring. It all depends on what kind of rides you enjoy most. Choose your Chainring Based on the TeethThe Relationship Between Chainring Teeth and Riding ScenariosWith more teeth, it means a bigger chainring. Bigger chainrings offer you harder gears, which are better for speed. As for smaller chainrings, they will make your pedaling easier. As a result, they are great for climbing or rough terrain. Choose the Correct Chainring Teeth Based on Your Riding GoalsSmaller chainrings are commonly used in high hills. The reason is that they make climbing easier. What's more, if you like spinning at a fast cadence or you're newer to riding, smaller chainrings will help make pedaling easier. As for Larger chainrings, they are suitable for flat roads because they are highly efficient for fast-riding. Things You Need to Consider When Purchasing Chainrings Bolt Circle DiameterThe Bolt Circle Diameter (BCD) is the measurement of the circle that runs through the center of all the bolts on your chainring. You’ll need to know BCD if you’re replacing a bolt-on chainring. BCD determines chainring compatibility. In order to fit more properly, the new chainring needs to match the crankset’s BCD and bolt pattern. With smaller BCDs, we use smaller chainrings. For example, a 130mm BCD fits a minimum 38t ring, while a 110mm BCD can go down to 33t. Direct-mount chainrings don’t have a BCD because they are mounted to a splined interface on the back of the crank. Materials of ChainringsChainrings are typically made from aluminum, steel, or carbon fiber. With different materials, the weight, durability, and performance will make a huge difference.Steel chainrings: They are tough and cheap, but are pretty heavy. They are commonly used on entry-level bikes.Aluminum chainrings: They are lightweight and don't rust easily. As a result, they are ideal for most performance bikes.Carbon Fiber chainrings: They are extremely lightweight and stiff but expensive. They are often used in high-end bikes. Conclusion
Choosing the right chainring can make a big difference in how your bike performs. When shopping for a chainring, please keep these factors in mind:
First, your bike type. With different types of bikes. Their chainring has its own unique features. Road bikes usually focus on speed and smooth shifting, so they often use lightweight chainrings. Mountain bikes prioritize control and simplicity. Therefore, their chainrings have smaller teeth. Gravel bikes can go either way depending on whether you ride on pavement or rough trails.
Second, the number of teeth. Bigger chainrings are great for speed and flat terrain, while smaller chainrings make climbing easier and are ideal for high hills. Your fitness level, cadence preference, and riding goals are key to your decision.
Third, Compatibility. You have to know the BCD of your crankset if you’re replacing a bolt-on chainring. To fit more properly, matching the new chainring to the crankset’s BCD and bolt pattern is essential. Also, make sure to choose a material that fits your needs. Steel is known for its durability and it is very cheap as well. Aluminum doesn't rust easily. As for carbon fiber, it is very light and stiff, but extremely expensive.
Ultimately, the best chainring is the one that suits your riding style, goals, and setup. Please take time to understand your needs and don’t hesitate to ask your local bike shop for help if you're unsure.
