Mountain biking is an ever-evolving sport, with manufacturers pushing the boundaries of design and technology to enhance performance. Yet, there’s one component that seems stuck in the past: crank length. Despite advancements in other areas, most mountain bikes still come with cranks that are, according to the latest science, unnecessarily long. Let’s delve into why this matters, the implications for your riding, and what you can do to optimize your setup.

The Science: Why Crank Length Isn’t What It Used to Be

For decades, crank length was largely determined by inseam length, with the assumption that taller riders needed longer cranks for leverage and efficiency. However, recent research, like that shared by Pinkbike, has turned this conventional wisdom on its head. Studies show that crank length has minimal impact on overall power output, cadence, or efficiency. Instead, it’s your riding style and biomechanics that should dictate your choice.

Key Findings:

• Inseam Isn’t King: Crank length based solely on your inseam length doesn’t account for variations in riding style, terrain, or bike geometry.
• Biomechanics Matter: Shorter cranks reduce knee strain and improve pedaling ergonomics, especially on steep climbs.
• Ground Clearance: Shorter cranks are less likely to strike obstacles, making them ideal for technical terrain.

Despite this evidence, most manufacturers continue to spec bikes with 170mm or 175mm cranks, regardless of the bike’s purpose or the rider’s needs. Why? It’s partly tradition, partly manufacturing convenience, and partly a lack of awareness among consumers.

The Benefits of Getting Crank Length Right

Upgrading to cranks that better suit your riding can be a game-changer. Here are the top reasons to consider switching:

1. Improved Efficiency and Comfort

Shorter cranks allow for a higher cadence, which reduces muscle fatigue on long rides. They’re also easier on your knees, making them a great choice for riders with joint issues or those who spend a lot of time climbing.

2. Better Ground Clearance

In technical terrain, pedal strikes can ruin your flow or even cause a crash. Shorter cranks reduce this risk, allowing you to focus on the trail instead of your feet.

3. Enhanced Handling

Shorter cranks can make it easier to shift your weight and maneuver the bike, especially in tight corners or on technical descents.

4. Minimal Downsides

Contrary to popular belief, shorter cranks don’t significantly reduce leverage or power. Studies like this one have shown that even tall riders can perform just as well, if not better, with shorter cranks.

What to Consider Before Ordering New Cranks

If you’re thinking about swapping out your cranks, here are some things to keep in mind:

1. Riding Style

• Enduro and Downhill Riders: Shorter cranks (e.g., 160mm or less) can improve control and reduce pedal strikes.
• XC and Marathon Riders: A balance between ground clearance and pedaling efficiency is key, so consider cranks in the 165mm range.
• E-Bike Riders: Cranks as short as 150mm can make a huge difference, as power output is less dependent on leverage.

2. Bike Geometry

A shorter crank arm can mean that (assuming you have the insertion space for it) you could fit a longer dropper post. Modern bike geometries, especially those with lower bottom brackets, make shorter cranks even more advantageous. Pairing short cranks with a dropper post can further enhance your ride.

3. Personal Preference and Testing

Testing is difficult, but with almost no downside and many upsides, the question should really be how short. To help you find a good starting point, tools like the 5Dev Crank Length Device can be incredibly helpful. This tool is available for free use by appointment at Boutique MTB in Vallentuna.

4. Brands to Explore

• 5Dev: Known for high-quality cranks in various lengths, ideal for enduro and DH.
• Miranda: Produces cranks as short as 150mm, including options for e-bikes.
• Appleman: Offers customizable solutions for discerning riders.

Disclosure: While we sell 5Dev cranks, this recommendation isn’t brand-specific. We believe most riders would benefit from shorter cranks when the time comes to upgrade.

Ready to Upgrade? Here’s How

Switching to shorter cranks doesn’t have to be daunting. Here’s a step-by-step guide:

1. Do Your Research: Use tools like the 5Dev Crank Length Device to find your ideal length. And if you do not have access to one, the above riding style-related lengths would be a good place to start for the vast majority of people (very, very tall or short-legged riders may want to adapt the numbers by 5 or 10mm, with shorter riders going shorter, etc.).
2. Consult a Pro: Sadly, almost no bike shop keeps stock of or works with manufacturers that make short crank arms. As a result, they may not be very knowledgeable or interested in promoting products they don’t sell themselves. However, if you’re lucky enough to have a local bike shop (LBS) that is very MTB-focused, with knowledgeable and honest staff who prioritize your needs over their bottom line, this could be a great starting point. While these shops might be rare, they do exist, and they’re worth seeking out.
3. Try Before You Buy: If a friend uses shorter cranks, see if they’ll let you take their bike for a spin. Just remember, like any change, it might take a few rides to feel completely natural. And if your friend is anything like me, you might need to leave your firstborn as a deposit before borrowing their prized bike!
4. Choose the Right Brand: Explore options from 5Dev, Miranda, and Appleman to find cranks that suit your needs and budget.

Conclusion: It’s Time to Rethink Crank Length

Shorter cranks offer numerous benefits, from improved comfort and efficiency to better handling and reduced risk of pedal strikes. While tradition and inertia have kept long cranks as the default, the science is clear: for most riders, shorter cranks are a better choice. Whether you’re an enduro racer, a weekend warrior, or an e-bike enthusiast, now’s the time to take a closer look at your setup.

Have you made the switch to shorter cranks? We’d love to hear your thoughts! Share your experiences in the comments below and let’s keep the conversation rolling. If you’re in Vallentuna, don’t forget to book a session with the 5Dev Crank Length Device at Boutique MTB to find your perfect fit.

Happy riding!