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Everything You Need to Know About Cranks

A crank is one of the most important components of a bicycle. It connects the pedals to the drivetrain and allows you to transfer power to the chain and ultimately to the rear wheel. But which crank is best for your bike, what should you look for when purchasing, and how do you install a crankset on your bike? Here you will find everything about cranks and their functions.

Let's start with the difference between a crank and a crankset:

Crank

A crank is a single component and specifically refers to the pedal arms that connect the pedals to the bottom bracket. Every bike has two cranks: a left and a right. The right crank is often equipped with a mounting point for the chainring or chainrings, which transfers the power of your pedal stroke to the chain.

Crankset

A crankset is the complete set, consisting of:

• The left and right crank.
• One or more chainrings (depending on the type of bike).
• Mounting bolts to attach the chainrings to the right crank.
• Sometimes the bottom bracket is also included with the crankset, especially with systems like Hollowtech II.

In short: the crank is a single component, while a crankset is a complete assembly that includes everything needed to transfer the power of your pedal stroke to the drivetrain of your bike.

Which Crank is Best for My Bike?

Choosing the right bicycle crank depends on the type of bike and its use. Ask yourself questions such as:

• What type of bike do I have? For a road bike or mountain bike, you often need a different crankset than for a city bike. A city bike crankset is simpler, while sporty bikes often use lighter and stiffer materials.
• What crank length do I need? Cranks come in various lengths, usually between 165 mm and 175 mm. Shorter cranks are suitable for smaller riders or a higher cadence. Longer cranks provide more leverage, which is useful for powerful cycling or climbing.
• Do I need a single, double, or triple crank? City bikes often have one chainring, while sporty bikes use multiple chainrings to provide a wider gear range.

Also, check if the crankset is compatible with your bottom bracket. Not every crank bicycle fits every system, so pay close attention to your bike's specifications.

What Should I Look for When Buying a Crank?

When purchasing a bicycle crank, there are a few important points to consider:

• Material: Cranks are often made of aluminum or carbon. Aluminum is strong and affordable, while carbon is lighter and more commonly used in sporty bikes.
• Compatibility: Check if the crank matches the number of gears on your bike (for example, 9-speed, 10-speed).
• Crank arm length: Choose a length that fits your body height and pedaling technique.
• Type of bottom bracket: Some cranks work with a square axle, while others are designed for modern systems like Hollowtech II or BB30.
• Use: For daily use, you can opt for a simple, durable model. For intensive sporty rides, a lightweight crankset is better suited.

How Does a Crank Work?

A crank works as a lever. When you push on the pedals, that force is transmitted through the bicycle pedal arm (the crank arm) to the chain and rear wheel. The principle is simple, but the execution can vary:

• On city bikes, the crank usually rotates around a simple bottom bracket with bearings.
• On sport bikes, stiffer cranks and an advanced bearing system provide more efficient power transfer.
• Cranks with multiple chainrings allow for shifting, making it easier to climb or ride faster.

The length and stiffness of the bicycle crank play an important role in how efficiently your power is transferred.

What Are Cranks Made Of?

Cranks are made from various materials, depending on the type of bike and intended use:

• Aluminum: Light, strong, and affordable. Commonly used in city bikes and entry-level sporty bikes.
• Carbon: Ultralight and stiff. Ideal for road bikes and mountain bikes, but more expensive and less resistant to hard impacts.
• Steel: Heavy but extremely durable. Often found on vintage or robust bikes, such as cargo bikes.
• Titanium: Light and strong, but very expensive. Mainly used in high-end bikes.

The material not only determines the weight but also the durability and price of the bicycle crankset.

How Do I Install a Crank?

Installing a bicycle crank requires precision, but with the right tools, you can do it yourself. Follow these steps:

• Remove the old crank: Use a crank puller to detach the old crank arms. First, loosen the bolts and then pull the crank off the bottom bracket.
• Check the bottom bracket: Ensure the bottom bracket is in good condition and suitable for the new crank. Replace it if necessary.
• Install the new crank: Slide the new crank arm over the bottom bracket. Make sure it is securely attached.
• Attach the crank bolts: Tighten the bolts securely with a torque wrench to prevent the crank from loosening while riding.
• Check for play: Ensure the crank rotates smoothly without play or resistance.

Always use a manual that matches the type of crankset for installation. With modern systems like Hollowtech II, the installation is slightly different than with a traditional square axle.

With the right crank and proper installation, you can get your bike running smoothly and efficiently again.