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Crank length is key to cycling efficiency, comfort, and performance. Choosing the right size depends on several factors. While a bike fitter can provide expert guidance, this article offers a solid starting point for your testing. I also share my experience switching from 175mm to 165mm cranks on my road bike.
KEY TAKEAWAY
Short cranks (165mm or shorter) promote a higher cadence, reduce joint strain, improve aerodynamics, and allow more aggressive cornering or riding on varied terrain. They are ideal for riders with limited flexibility, those working on cadence efficiency, and criterium racers.
Long cranks offer greater leverage and torque, helping you generate maximum power more quickly, which benefits sprinters. However, they can increase the risk of knee strain and reduce pedaling efficiency due to a lower cadence.
Before you decide what crank length is best for you, I recommend experimenting and trying different setups.
Pros and Cons of Short vs. Long Cranks
The following table summarizes the pros and cons of short vs. long cranks.
| Cranks | Pros | Cons |
|---|---|---|
| Short Cranks (165mm or shorter) | • Reduced joint strain • Encourages higher cadence • Improve aerodynamics thanks to lower riding position • Improved pedal clearance • Reaching maximum power takes shorter | • Lower mechanical leverage and less torque • Can feel unnatural for riders used to longer cranks |
| Long Cranks (170mm or longer) | • Greater mechanical leverage leading to more explosive acceleration • Allow generating maximum power quicker • May feel more natural to taller riders | • Increased joint strain • Lead to a lower cadence • Can lead to a less aerodynamic riding position • Increased risk of pedal strikes • Reaching maximum power takes longer |
Let’s now discuss the pros and cons in depth.
Power and Leverage
Crank length directly affects mechanical leverage. Longer cranks allow for greater torque and power transfer, which is useful for sprinting and attacking. You will reach your maximum power more slowly than with shorter cranks, but the initial power output is greater.(Source)
Shorter cranks require a higher cadence to generate the same power output, reducing the ability to push heavy gears efficiently. When sprinting, my speed increases more gradually and less sharply.
If you care about the average power, I didn’t see any negative effects. I noticed that I’m less tired after long rides. However, this might also be because I switched bikes, and I engage my glutes better on the new one. I describe this more in my Winspace Agile review.
According to multiple studies, crank length does not significantly impact maximum power output. A 2001 study found that the optimal crank length is 170mm for most adults, with maximum power varying by only 4% between the shortest (120mm) and longest (220mm) crank lengths tested.(Source)
Similarly, a 2011 study concluded that cyclists can select crank lengths based on personal preference or other factors without significantly affecting their maximum power output.(Source)
Cadence
Cadence is the number of pedal revolutions per minute (RPM). Shorter cranks naturally promote a higher cadence. I noticed an increase of around 5 RPM when switching from 175mm to 165mm cranks.
Is slower cadence due to longer cranks an issue? Well, it could be because you have to apply more force, which is tiring your muscles more quickly.(Source) This is a topic that coaches from the Alpecin Deceunick team often discuss at Zwift Academy when observing new talents.
Road races are long and require a lot of endurance. It’s focused on efficiency, and shorter cranks are one factor that can contribute to that efficiency. Tadej Pogačar switched from 172.5mm to 165mm cranks and inspired many others to do the same.
Joint Strain
Crank length influences the range of motion in the hips, knees, and ankles. Longer cranks require a greater range of motion and leverage than shorter cranks, leading to higher joint strain.
I always struggled a bit with knee pain with 175mm cranks. But after switching to 165mm cranks, the pain is gone. It’s worth noting that I am 185cm, which should correspond to a crank length of 175mm.
Aerodynamics
Aerodynamics is critical in road racing, time trials, and triathlons. However, it gets increasing attention in other disciplines, such as gravel biking. Shorter cranks lead to increased saddle height but a more aggressive riding position due to the larger drop. This means you will have a lower frontal area and, therefore, achieve higher average speeds when pushing the same power.
I recommend watching the following video, where you’ll see a clear illustration of the riding position change.
Cornering and Pedal Strikes
Crank length affects ground clearance and pedal strikes. If you are a mountain biker or criterium racer who pushes it to the limits in the corners, shorter cranks could greatly benefit you. They provide greater clearance, allowing you to lean your bike more while still pedaling.
With longer cranks, you increase the risk of pedal strikes, particularly in aggressive cornering or technical trails. This can be problematic, especially if you don’t have a good sense of how much you can lean the bike to avoid hitting the ground with the pedal and falling off.
What Are the Common Crank Lengths?
Most bikes today come with crank lengths between 165mm and 175mm. However, some manufacturers offer shorter or longer options. It’s commonly believed that taller riders should use longer cranks. But I recommend trying different lengths to find what works best for you.
Cycling is a traditional sport where changes happen slowly. For example, larger bike sizes come with wider handlebars. However, they may not suit everyone. I use 380mm handlebars, even though most bikes my size come with 420mm bars.
Many bikes come with standardized crank lengths (170mm or 172.5mm), regardless of a rider’s height or biomechanics. This can lead to inefficient pedaling, discomfort, and increased injury risk.
Don’t be afraid to experiment. You don’t have to buy new cranks right away—just borrow a pair and test them out.
How to Choose Crank Length?
Selecting the right crank length depends on several factors, including leg length, biomechanics, and riding style. The best approach is to listen to your body and be open to trying something different. I switched to cranks 10mm shorter than what I was used to, and I would never go back. In my experience, a 2.5mm difference—the standard increment—is barely noticeable.
If you’re sensitive to small changes, try adjusting your crank length by 5mm to feel a real difference. You can also use my crank length calculator for recommendations. A professional bike fit specialist will also help you find the best crank length based on your biomechanics and goals.
How to Adjust Your Bike Fit If You Change Your Crank Length?
Switching crank lengths requires adjustments to your bike fit. Here is a simplified guide:
- Saddle Height – Shorter cranks require raising the saddle, while longer cranks may require lowering it. The height change should be the same as the crank length difference.
- Saddle Fore-Aft Position – To ensure proper knee alignment over the pedals, you should also experiment with adjusting the fore-and-aft position. Shorter cranks require moving the saddle forward, while longer cranks require moving it back.
- Handlebar Position – Shorter cranks allow you to sit in a more aggressive aero position, which may require lowering the handlebars by removing spacers.
I recommend being careful with the changes and changing only one variable at a time. This way, you can isolate how the change impacts your riding.
Conclusion
There is no one-size-fits-all crank length. The best choice depends on your biomechanics, riding style, and personal preference. The best way to find the ideal crank length is through experimentation.
Try different crank lengths by borrowing or swapping cranks, and see how they impact your comfort and performance. Don’t forget to adjust your saddle height and fore-aft position, as both need fine-tuning after a crank length change.
Have you ever changed your crank length? What difference did it make for you? Share your experience in the comments below!
I get knee pain when I ride 165mm. I ride a lot of uphill and have changed to 175mm many years ago and the knee pain has disappeared. The longer the crankarm the bigger and longer part of the muscle is used.
Yeah, bike fit is very individual, but from what I learned, the majority of people benefits from using shorter ones. But I am glad you solved your issues. How tall are you?