What Crank Length Should I use on a Fixie

On a fixed gear bike, we want to use short cranks, doubly so if on a tracklocross bike. Ideally 160- 165mm. That is all the answer you need, but feel free to read on if you would like to discover the rationale behind why this is so. Remember and look after your knees, they are kind of important.

Improved Pedal Clearance in Tight Turns

One of the primary reasons for using shorter cranks on a fixie is the need for better pedal clearance, especially true if you are riding tracklocross and want to avoid hitting all the trail debris.

Longer crank arms increase the risk of “pedal strike,” where the pedal or foot contacts the trail or a kerb during a turn, potentially leading to a crash. Shorter cranks reduce the likelihood of pedal strike, allowing you to keep pedalling without adjusting their position or cadence. This advantage is especially needed in tracklocross where tree roots and rocks are likely to be in your way and if you can limit hitting them your ride will be more enjoyable.

Higher Cadence Capabilities

Fixed gear cycling places a heavy emphasis on cadence, as you are not using mechanical gears, your legs become the gears in effect. Shorter cranks allow you to pedal at a higher cadence with reduced muscular strain, facilitating rapid accelerations and sustained efforts over extended periods.

At the traffic lights, or about to hit a short sharp climb, bursts of speed are critical, the ability to spin the pedals quickly and efficiently is a major advantage. Shorter cranks reduce the angular displacement of your legs, allowing for quicker turnover and enabling you to maintain higher speeds with less effort. Less effort is always better.

Reduced Joint Stress and Improved Comfort

From a biomechanical perspective, shorter cranks place less strain on your knees and hips by reducing the range of motion required during each pedal stroke. This reduced range of motion can be particularly advantageous for couriers who spend long hours riding, and usually at high intensity.

With longer cranks, the increased knee flexion at the top of the pedal stroke can lead to discomfort or even injury over time. Shorter cranks help mitigate these issues by promoting a more natural and efficient pedalling motion, reducing the likelihood of overuse injuries and improving overall comfort during intense efforts.

Just for Fun: Enhanced Aerodynamics

Aerodynamics plays a significant role in cycling, according to the media, as riders strive to minimise air resistance to achieve maximum speed. Shorter crank arms allow for a more compact and aerodynamic riding position by reducing the overall range of leg movement. With shorter cranks, a cyclist’s knees travel a shorter vertical distance, which can help them achieve a lower and more streamlined profile.

By minimising excessive leg movement and reducing the upward and downward motion of the knees, shorter cranks contribute to a smoother airflow around the rider’s body. This aerodynamic gain is particularly beneficial when trying to get to the bar, where every watt of energy saved can lead to significant improvements in partying.

We can also talk about optimised power transfer, but that makes me feel like we should all just be in the velodrome donning Lycra and telling everyone about how you could have been a contender. Hopefully, now you understand why shorter cranks are awesome, and you are going to run shorter cranks to save your knees.