The length of your crankarms influences more than leg extension—it affects cadence efficiency, joint stress, and power delivery. Most road bikes ship with 170mm or 172.5mm arms, but shorter (165mm) and longer (175mm) options are gaining traction.
Shorter arms improve hip clearance and cadence, making them ideal for riders with limited flexibility or high-RPM pedaling styles. Longer arms may favor riders seeking more leverage and torque, but can increase strain on knees and hips. Proper fit matters most.
In the world of road cycling, marginal gains make all the difference. While most riders focus on frame geometry, saddle height, or gear ratios, one component often overlooked is crankarm length. Whether you’re riding 165mm, 170mm, or 175mm crankarms, the length of those levers beneath your feet significantly affects performance, comfort, and biomechanics.
Why Crankarm Length Matters
Crankarms act as mechanical levers, converting your pedaling motion into torque. Their length influences your cadence, power delivery, joint angle, and overall fit on the bike. That’s why it’s not just about leg length—it’s about how the crankarm interacts with your riding style and body mechanics.
A longer crankarm increases the torque you can apply per pedal stroke, which can benefit low-cadence riders, sprinters, or those who frequently ride steep climbs. However, longer arms also increase the range of motion your knees and hips go through, which can lead to overuse injuries or inefficiencies, especially if your flexibility or saddle position doesn’t align well.
Conversely, shorter crankarms reduce joint angles, improve hip clearance, and allow for a more aerodynamic torso position. Riders with shorter inseams or limited flexibility often report greater comfort and smoother cadence using 165mm cranks. They’re also popular among high-cadence riders who prioritize pedal stroke fluidity and knee health over maximum leverage.
165mm Crankarms: Compact, Efficient, and Fast-Spinning
Popular among smaller riders and time trialists, 165mm cranks reduce the circular arc the foot must travel, minimizing hip closure at the top of the stroke. This can enhance comfort, prevent impingement, and improve cadence control. In disciplines like triathlon and aero racing, this smaller crankarm length also enables a lower and more aggressive position on the bike.
170mm Crankarms: The Versatile Standard
Most road bikes ship with 170mm or 172.5mm crankarms. These lengths provide a good balance between power and cadence and suit a wide range of rider heights (typically 165–180 cm). It’s a conservative, all-purpose length that works for most but may not optimize every aspect of performance or fit.
175mm Crankarms: Leverage and Torque at a Cost
For taller riders or those seeking maximum torque on steep gradients, 175mm crankarms offer extended leverage. However, that extra length also raises knee tracking demands, particularly at the top of the stroke. For some, this can result in hip tightness or knee pain over longer rides, especially if the rest of the bike fit doesn’t adjust accordingly.
It’s Not Just About Height. It’s About Fit
Rider height alone shouldn’t dictate crankarm choice. Femur length, pelvic rotation, saddle setback, and cadence style all play roles. Bike fitters increasingly use motion capture systems to identify crankarm length as part of a dynamic fitting process. This data-driven approach reveals that a shorter crank can often improve comfort, aerodynamics, and pedal economy, even for taller riders.
Carbon Cranksets and Modular Fit Options
Brands like QO and ROTOR now offer modular carbon cranksets with interchangeable arms, making it easier than ever to fine-tune crank length without sacrificing weight or stiffness. QO’s ultralight carbon arms are available in 165mm to 175mm options, with a focus on power transfer and joint-friendly ergonomics. Whether you’re refining your race fit or looking to relieve joint stress, these modular systems enable better personalization than ever.
CarbonRaw Tips and Conclusion
Crankarm length is more than a static measurement, it’s a performance variable. Whether you’re seeking smoother cadence, increased torque, or improved joint health, the right crank length plays a pivotal role. For riders pushing for every advantage, evaluating and optimizing crankarm length could be the simplest upgrade with the biggest return.