What is A Crankset on A Bicycle? Everything You Need to Know

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A crankset is the component that converts the pedaling motion into rotational motion that drives the chain and the rear wheel of a bicycle. It consists of one or more chainrings (also called sprockets) attached to a crank arm that connects to a pedal.

The earliest cranksets were made of wood and had a single chainring with fixed teeth. Later, metal cranksets with detachable chainrings and variable gearing were developed. Modern cranksets come in various types, sizes, materials, and configurations to suit different kinds of bicycles and riding styles.

But no worries. The article will explain all items related to bicycle crankset, such as its parts, types, how it works, its sizes, and how to choose the right one for your bike.

Crankset Parts

Basically, for a crankset, there are two major parts, i.e. the chainring and the crank arm, but also some other accessory parts.

Chainring

The chainring is a circular metal plate with teeth that engages with the chain and transfers power to the rear wheel. It is the primary component of the crankset that connects your pedal strokes to forward motion. Chainrings come in different numbers, shapes, and sizes, depending on the type of bicycle and the desired gear range. The number of chainrings on a crankset can vary, with most road bikes having two chainrings, while mountain bikes can have one, two, or even three. The shape and size of the chainrings also affect the gear ratio and the ease of pedaling.

Crank Arm

The crank arm is a metal or carbon rod that connects the pedal to the spindle. It is the part of the crankset that you push with your legs to generate power. Crank arms come in different lengths and angles, allowing riders to find the optimal position for their biomechanics and riding style. A longer crank arm can provide more leverage, making it easier to pedal uphill, while a shorter crank arm can increase pedaling cadence and efficiency. The crank arm is attached to the spindle using a bolt or a spline system, ensuring a secure connection.

Spindle

The spindle is a metal axle that passes through the bottom bracket and holds the chainrings and crank arms together. It is a critical component of the crankset that enables smooth rotation and transfers the power generated by the rider to the drivetrain. Spindles come in different diameters and lengths, depending on the type of bottom bracket and frame compatibility. In some crankset designs, the spindle is integrated with one of the crank arms, while in others, it is a separate component.

Crank Spider

The crank spider is a metal star-shaped structure that connects the chainrings to the spindle. It plays a vital role in maintaining the proper alignment of the chainrings and ensuring efficient power transfer. The number of arms on the spider depends on the number of chainrings and the bolt circle diameter (BCD). Some cranksets have the spider integrated with one of the crank arms, while others have a separate spider. The spider is securely attached to the crank arm or the spindle, depending on the design.

crankset parts

Crankset Types

There are many ways to categorize the crankset, such as the way based on the number of chainrings, the way based on the attachment method to the bottom bracket, the way based on the shape and size of chainrings, the way based on the shape and size of the crank arm, etc.

To make it simple, here we just select two of them to show you the types of the crankset, i.e. the number of chainrings and the attachment method to the bottom bracket.

Here are the three main types of cranksets based on the number of chainrings:

1. Single Chainring (1x or One-By) Cranksets

Single chainring cranksets, also known as 1x or one-by cranksets, feature only one chainring. They are commonly paired with a wide-range cassette, which is a set of sprockets on the rear wheel. This combination provides enough gears to tackle various terrains.

Pros:
– Simple and lightweight design.
– Reliable and less prone to chain drop.
– Easy to shift and maintain.

Cons:
– Limited gear range.
– May require a special rear derailleur or a chain guide for optimal performance.

2. Double Chainring (2x or Two-By) Cranksets

Double chainring cranksets, also known as 2x or two-by cranksets, feature two chainrings of different sizes. They are usually paired with a 10- or 11-speed cassette to provide a wide range of gears suitable for various terrains.

Pros:
– Versatile and efficient
– Smooth shifting
– Compatible with most bikes and drivetrains

Cons:
– Complex and heavier compared to single chainring cranksets
– More prone to chain drop
– Require more frequent shifting and maintenance

3. Triple Chainring (3x or Three-By) Cranksets

Triple chainring cranksets, also known as 3x or three-by cranksets, feature three chainrings of different sizes. They are usually paired with a 9- or 10-speed cassette, providing a very wide range of gears suitable for steep hills and heavy loads.

Pros:
– Very versatile and suitable for challenging terrains
– Compatible with most bikes and drivetrains

Cons:
– Very complex and heavier compared to single or double chainring cranksets
– More prone to chain drop
– Require more frequent shifting and maintenance
– May cause cross-chaining, reducing efficiency and wearing out components faster

Apart from the number of chainrings, the attachment method of the crank arm to the bottom bracket is another crucial aspect to consider. Here are some common attachment methods:

1. Square Taper

The square taper is the most common and traditional attachment method. The crank arm has a square hole that fits onto a square spindle, which connects the two sides of the bottom bracket.

Pros:
– Simple and cost-effective
– Reliable and easy to install and remove

Cons:
– Relatively heavier compared to other attachment methods
– Prone to creaking and loosening if not properly maintained
– May damage the crank arm or spindle if overtightened or removed improperly

2. Octalink

Octalink is a proprietary attachment method developed by Shimano. The crank arm has an eight-spline hole that fits onto an eight-spline spindle.

Pros:
– Light and stiff design
– Reliable and easy to install and remove

Cons:
– Relatively expensive
– Incompatible with other brands and models
– May damage the crank arm or spindle if overtightened or removed improperly

3. ISIS

ISIS is a standard attachment method developed by several manufacturers. The crank arm has a 10-spline hole that fits onto a 10-spline spindle.

Pros:
– Light and stiff design
– Reliable and compatible with most brands and models

Cons:
– Relatively expensive
– Prone to creaking and wearing out if not properly maintained
– May damage the crank arm or spindle if overtightened or removed improperly

4. Hollowtech II

Hollowtech II is another proprietary attachment method developed by Shimano. The crank arm has a 24-mm hollow spindle that is integrated with the right side of the crankset and fits into a bearing cup on the bottom bracket shell.

Pros:
– Very light and stiff design
– Very reliable and easy to install and remove

Cons:
– Relatively expensive
– Incompatible with other brands and models
– May require a special tool for installation and removal

Cranksets Sizes

The size of a crankset mainly refers to three measurements: the length of the crank arms, the diameter of the chainrings, and the Q-factor.

Crank Arm Length

One of the main measurements when it comes to cranksets is the length of the crank arms. This refers to the distance between the center of the bottom bracket axle and the center of the pedal spindle. Crank arms typically come in lengths ranging from 165mm to 180mm, with the most common sizes being 170mm and 175mm.

So, how does the length of the crank arms affect your pedaling efficiency and comfort? Let’s take a closer look:

1. Leverage and Power Output: Longer crank arms give you more leverage, allowing you to exert more force on the pedals. This can be beneficial for riders who prioritize power output, such as sprinters or those riding on hilly terrains. However, it’s important to note that longer crank arms also require more leg movement, which can affect your pedaling cadence and comfort.

2. Leg Movement and Comfort: On the other hand, shorter crank arms require less leg movement, making them more suitable for riders who prioritize a higher cadence or have shorter legs. Shorter crank arms can also provide a more comfortable pedaling motion, reducing the risk of knee and hip strain.

Finding the right crank arm length for you is a matter of personal preference and biomechanics. It’s essential to consider factors such as your leg length, riding style, and the type of terrain you usually ride on. Consulting with a bike fit specialist can help you determine the optimal crank arm length for your needs.

The Diameter of the Chainrings

The diameter of the chainrings refers to the number of the tooth. Chainrings come in various sizes, with the most common ones being 50/34 (compact) and 53/39 (standard) for road bikes, and 32/22 (double) or 30/28/26 (triple) for mountain bikes.

Here’s how the diameter of the chainrings affects your gear ratios and pedaling effort:

1. Gear Ratios: The diameter of the chainrings determines your gear ratios, which affect your speed and ability to tackle different terrains. Larger chainrings, such as a 53-tooth one, provide higher gear ratios, allowing you to achieve higher speeds on flat roads or descents. On the other hand, smaller chainrings, like a 34-tooth one, offer lower gear ratios, which make climbing steep hills or riding off-road easier.

2. Pedaling Effort: It’s important to note that larger chainrings require more pedaling effort to maintain a certain speed. This means that if you’re riding with a larger chainring, you’ll have to push harder on the pedals to achieve the same speed as someone using a smaller chainring.

Q-Factor

The final measurement we’ll discuss is the Q-factor. The Q-factor refers to the distance between the outside of one crank arm and the outside of the other, measured laterally through the midline of the bottom bracket. It plays a role in your overall pedaling comfort and biomechanics.

1. Stability and Clearance: A wider Q-factor provides more stability, especially for riders who prefer wider tires or ride on rough terrains. It also offers more clearance, reducing the risk of your feet hitting the crank arms during pedaling.

2. Alignment and Interference: On the other hand, a narrower Q-factor can provide a more aerodynamic position and a more natural pedaling motion. However, it can also cause your feet to be too close together, potentially interfering with your frame or chainstays.

Finding the optimal Q-factor is a personal preference and depends on your anatomy, biomechanics, and riding style. It’s crucial to consider factors such as hip, knee, and foot alignment when determining the ideal Q-factor for your comfort and performance.

How to Choose a Crankset for Your Bicycle

There are just a bunch of factors which will have an impact on how you choose a crankset for your bicycle, such as the crankset compatibility with your bike, your bike type, riding style, terrain, personal preference, budget, etc.

Compatibility

Before diving into the specifics of crankset selection, it’s important to understand the concept of compatibility. A compatible crankset is one that matches the bottom bracket shell of your bike frame, the chainrings’ bolt circle diameter (BCD), the chainline, and the speed of the chainrings.

In the following, we will explain them one by one to you.

The first step in compatibility is to ensure that the bottom bracket standard of the crankset matches the bottom bracket shell of your bike frame. There are various types of bottom brackets, such as threaded, press-fit, or BB30, each with different diameters and widths. It’s essential to verify that the crankset you choose has the same bottom bracket standard as your bike. If there is a mismatch, you may need to use an adapter to make them compatible.

The BCD refers to the diameter of the circle that passes through the center of the bolts securing the chainrings to the crank arms. It’s crucial to select a crankset with a BCD that matches your original one, or else you won’t be able to install or change chainrings. Check the BCD of your crank arms and ensure that the chainrings of the new crankset have the same BCD.

The chainline is the distance from the centerline of the frame to the middle of the chainring(s). A mismatched chainline can lead to poor shifting, chain wear, or chain drop. To avoid these issues, make sure the chainline of the crankset you choose matches the spacing of your rear hub and cassette. If needed, you can use spacers or offset chainrings to adjust the chainline.

The speed of the chainrings refers to how many rear sprockets they are designed to work with. Using chainrings with a different speed than your chain and derailleur can result in poor shifting, chain noise, or chain rub. Verify that the crankset you choose has the same speed as your original one or use a compatible chain and derailleur to ensure smooth operation.

Bicycle Type

Different types of bikes require specific cranksets designed to meet their unique purposes and features. Let’s explore the most common bike types and the corresponding crankset characteristics:

Road Bikes: Road bikes typically have double or triple chainring cranksets with smaller chainrings (usually 34-53 teeth) and longer crank arms (usually 170-175 mm). These cranksets are designed to provide high-speed performance and efficiency on smooth roads.

Mountain Bikes: Mountain bikes commonly feature single or double chainring cranksets with larger chainrings (usually 28-38 teeth) and shorter crank arms (usually 165-175 mm). These cranksets prioritize low-speed torque and clearance for tackling rough trails.

Touring Bikes: Touring bikes often have triple chainring cranksets with a wide range of chainrings (usually 22-50 teeth) and medium-length crank arms (usually 170-175 mm). These cranksets offer versatility and endurance for long-distance and loaded riding on various terrains.

Gravel Bikes: Gravel bikes typically utilize single or double chainring cranksets with medium-sized chainrings (usually 30-46 teeth) and medium-length crank arms (usually 170-175 mm). They strike a balance between adaptability and stability for mixed-surface riding on roads, trails, and gravel.

Cyclocross Bikes: Cyclocross bikes usually have single or double chainring cranksets with smaller chainrings (usually 36-46 teeth) and shorter crank arms (usually 165-172.5 mm). These cranksets provide agility and responsiveness for fast and technical riding on muddy and slippery courses.

Hybrid Bikes: Hybrid bikes commonly feature double or triple chainring cranksets with a wide range of chainrings (usually 28-48 teeth) and medium-length crank arms (usually 170-175 mm). These cranksets prioritize comfort and convenience for casual and recreational riding on urban and suburban roads.

BMX Bikes: BMX bikes typically have single chainring cranksets with very small chainrings (usually 25-36 teeth) and very short crank arms (usually 140-165 mm). These cranksets are designed to provide strength and stability for extreme and acrobatic riding on ramps, jumps, and tracks.

Track Bikes: Track bikes usually have single chainring cranksets with very large chainrings (usually 44-55 teeth) and medium-length crank arms (usually 165-175 mm). These cranksets prioritize speed and power for competitive and fixed-gear riding on velodromes.

Electric Bikes: Electric bikes may have single or double chainring cranksets with additional features such as sensors, motors, or batteries to provide assistance and support for easier and faster riding on various terrains.

Recumbent Bikes: Recumbent bikes often require custom-sized and shaped cranksets to fit their unique design and rider position.

Riding Style

Your riding style also plays a role in choosing the right crankset. Consider the following preferences and requirements based on different riding styles:

Speed-Oriented Riders: If you prioritize speed, you’ll likely prefer lighter, stiffer, and more aerodynamic cranksets. These cranksets typically have fewer chainrings and larger chainrings to maximize efficiency and performance on flat and smooth roads.

Torque-Oriented Riders: Riders who prioritize torque for climbing steep hills and rough terrains may prefer heavier, stronger, and more durable cranksets. These cranksets typically have more chainrings and smaller chainrings to optimize leverage and traction.

Endurance-Oriented Riders: For those who seek versatility, reliability, and comfort, cranksets with a wide range of chainrings and medium-sized chainrings are ideal. These cranksets adapt to various conditions and distances encountered on mixed-surface roads.

Fun-Oriented Riders: If you simply want to enjoy the ride without worrying too much about shifting and maintenance, cranksets with fewer chainrings and medium-sized chainrings are a good fit. These cranksets offer simplicity, ease, and fun on urban and suburban roads.

Terrain

Considering the terrain you’ll be cycling on when selecting a crankset is also important.

Flat Terrain: If you’ll primarily be riding on flat terrain, you’ll require less gear range and more speed. Cranksets with fewer chainrings and larger chainrings are suitable for maximizing speed in these conditions.

Hilly Terrain: For hilly terrain, you’ll need more gear range and more torque. Cranksets with more chainrings and smaller chainrings provide the necessary leverage and traction for climbing steep hills.

Mixed Terrain: If you’ll be cycling on a mix of terrains, you’ll need a balance of gear range, speed, and torque. Cranksets with a wide range of chainrings and medium-sized chainrings offer the versatility required for tackling diverse terrains.

Conclusion

When you get here, we have pretty much finished all the topics about what a crankset is on a bicycle, at least for my knowledge.

Thank you for reading this article. I hope you found it helpful and informative. If you have any feedback or questions, please feel free to leave a comment below. Happy cycling!

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AUTHOR

Randy Joycelyn

Randy is the founder and editor of Cycling Soigneur. He has been passionate about cycling since he was a kid. He has been riding bikes for over 10 years. Cycling has just become a part of life.

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