Crank length in bike fitting – better understanding comfort, performance and efficiency

"Pogacar does it!" Hallelujah, finally a trend in professional cycling that I support: switching to a shorter crank. Even though the advantages of shorter cranks have been well documented for quite some time and published in many magazines for years, I'm glad that some pros are now doing it too. This means that our recommendation to switch to a shorter crank during bike fitting is far less likely to be perceived as exotic. This saves me calls from repair shops refusing to install a shorter crank, saying, "He's not that small, we won't fit him a 160mm crank!" Body size has very little to do with the correct crank length; seating position, mobility, and possible injuries or illnesses of the cyclist are far more important in determining the choice of crank length.

Why crank length is crucial

Crank length influences the flexion of the joints, the range of motion during pedaling, and the leverage ratios during power transmission. It is therefore a key factor when it comes to pain relief, efficiency, and choosing the optimal riding position—especially for those with hip or knee joint restrictions.

No lower performance due to shorter cranks

The good news first: A shorter crank doesn't result in a loss of performance. Numerous studies show that shorter crank lengths don't negatively impact performance or energy consumption.

Spanish researchers were pioneers in this field. They had cyclists pedal at submaximal loads (150 W, 200 W, and 250 W) and with different crank lengths from 165 mm to 175 mm. The results: Neither heart rate nor energy consumption changed significantly across the different crank lengths.

An older study with an even wider range of 145–195 mm crank length also came to a similar result: mechanical efficiency remained constant regardless of crank length.

Other studies even describe a performance advantage of shorter cranks, attributing this to the lower neuromuscular demands of pedaling. It sounds stressful at first, but it's actually quite simple: The muscles have to contract over a shorter distance with each pedal stroke. This is much more relaxing for the nervous system with a short crank than with a long one. The improved efficiency results in the described performance advantage.

Higher cadence as a pleasant side effect and not as a necessary evil

Another advantage of shorter cranks is their effect on cadence. Although it is sometimes mistakenly assumed in the literature that shorter cranks lead to higher cadence with the same gear ratio, the mechanical gear ratio remains the same with the same chainring. Imagine you only change one crank arm. Even then, both crank arms would rotate around the bottom bracket the same number of times. The observed higher cadence values ​​are based on the neuromuscular relief described above: the shorter muscle movement path makes it easier for the nervous system to pedal faster. In practice, this leads to gear changes more often and earlier than during a Sunday afternoon quiz at the local pub. The interplay of lower muscular effort per crank revolution and gear shifting behavior enables a more pleasant and efficient cadence. You can expect relaxation across the board.

Increase comfort, improve joint health

Another advantage: lower joint flexion angles protect the knee and hip joints. This can provide noticeable relief and have a preventative effect, especially for conditions like hip impingement or knee osteoarthritis. So, if you have knee problems that you just can't seem to get under control, persistent osteoarthritis, or hip problems like impingement or dysplasia, do yourself and your collagen-coated calcium sockets a favor and switch to a shorter crank.

For whom shorter cranks are particularly worthwhile

• Beginners: benefit from easier coordination and less muscular strain.
• Athletes with disabilities: less bending means more comfort and safety.
• Long-distance riders: shorter cranks allow for a more open riding position and reduce fatigue.

One study even showed that 145mm crank lengths resulted in up to 5.5% higher performance for beginners compared to standard 175mm cranks. So if you're riding with a 180mm crank or longer (🙏God forbid🙏), consider a shorter crank.

Exception: Sprint & Criterium

In very short, intense race formats like sprints or criterium races, longer cranks can offer advantages due to the larger lever. Explosive power in the final sprint can be crucial here. Nevertheless, even in these disciplines, the riding position is important, and shorter cranks allow for a more aggressive aero position and pedaling through corners.

Frequently asked questions about crank length

• Do I have pain or limitations in my knee or hip?
  → Shorter crank
• Do I tend to do long and steady rides?
  → Shorter crank
• Do I ride short and explosively – like sprints or criteriums?
  → Longer cranks may be useful but don’t forget hips, knees and cornering
• I changed my crank – do I need to adjust anything?
  → Yes. Seat height must be increased when shortening the crank.
• Does every crank length fit every bike?
  → Not necessarily. If in doubt, ask your trusted mechanic

Conclusion

Shorter cranks don't mean less power; quite the opposite: They can improve comfort, efficiency, and joint health, thus positively impacting performance. A shorter crank is particularly beneficial for beginners, long-distance riders, or those with knee and hip problems. Therefore, crank length should always be considered during a thorough bike fitting. This allows you to objectively determine which length is ideal for your goals and anatomy... probably a short one.