🚴 Short Cranks for 30 Days & The Results Shocked Me

Over 1,000 kilometers and thirty days, a seasoned cyclist exchanged his customary 175 mm crank arms for FSA’s K-Force Team Edition 165 mm set to determine whether the burgeoning interest in shorter crank lengths among professional riders represents a genuine performance and comfort advancement or merely a passing trend. Sparked by sightings of Tour de France champions Tadej Pogačar and Jonas Vingegaard aboard bikes fitted with ever‐shorter cranks, our subject embarked on a systematic investigation blending personal experience, controlled power tests, and expert insights from Dr. Borut Fonda—lead scientist at absoluteBLACK’s Science Lab in Slovenia.

🔬 1. Motivation and Experimental Design

Crank length—the distance between the center of the bottom bracket and the pedal axle—has traditionally been matched to rider height or inseam. Taller riders, by this logic, should use longer cranks to maximize leverage and torque, especially during climbs. However, recent trends in the pro peloton are challenging this notion. Shorter cranks are now being used by taller riders to achieve better aerodynamics, more fluid pedal motion, and reduced joint strain.

This experiment set out with two primary goals: First, to assess whether the use of shorter cranks would alleviate the rider’s chronic lower-back stiffness, hip tightness, and saddle sores. Second, to determine whether switching to 165 mm cranks would affect the cyclist’s sprinting power, climbing efficiency, and time-trial output. This dual approach combines both subjective physical impressions and hard data from power meters and heart rate monitors.

👨‍⚕️ 2. Biomechanical Insights from Dr. Borut Fonda

Dr. Fonda’s lab is equipped with cutting-edge tools including high-resolution 3D motion capture, force-measuring pedals, and real-time metabolic analysis to evaluate how changes in bike setup affect rider physiology. According to Fonda, shorter cranks can significantly improve pedaling dynamics by aligning muscle force more directly with crank rotation. This improves efficiency by minimizing wasted lateral forces that don’t contribute to forward motion.

Moreover, the reduction in hip flexion angles at the top of the stroke lessens the risk of arterial kinking, a condition that impedes blood flow in competitive cyclists. With less compression on the iliac artery, blood oxygen delivery improves, particularly during long endurance rides. These findings are consistent with growing empirical support for shorter cranks in time-trial setups, where aerodynamic posture is paramount.

📊 3. Baseline Data & Rider Background

The test rider stands at 2.03 m and has been cycling competitively and recreationally for over two decades. Until this experiment, he had exclusively ridden cranks in the 175 mm to 177.5 mm range. He reported persistent lower-back pain beginning at the four-hour mark on long rides, hip discomfort after hilly sessions, and frequent saddle sores exacerbated by his aggressive riding posture.

Performance metrics before the switch included a peak sprint of ~1,400 W over 5 seconds and an average power of 462 W over a 3.6 km climb at 8.7% grade. These numbers provided a solid benchmark against which to measure the impact of the shorter cranks.

🚵 4. The 1,000 km Adaptation Period

During the initial adaptation phase, the rider experienced a learning curve. The first 50 km ride felt awkward and unnatural. The crank stroke felt abbreviated, like pedaling in tight loops. However, within the first 200 km, cadence increased from an average of 84 to 88 rpm. This adjustment was necessary to compensate for the loss of leverage and to maintain comparable power outputs without fatiguing prematurely.

By the 700 km mark, the rider noted substantial changes in comfort. Hip tightness diminished, saddle sores disappeared, and aero positioning felt more sustainable. On indoor rides using a 170 mm crank-equipped smart trainer, transitions to 165 mm cranks felt natural and seamless, further reinforcing the validity of the change.

🧭 5. Long Ride Comfort: The Ultimate Test

Over several endurance rides ranging from 5 to 10 hours, the rider documented dramatic improvements. Back pain dropped to 2/10 from a baseline of 6/10. Hips and knees felt more mobile and less inflamed post-ride. Enhanced recovery was also evident—less soreness the following day and no need for extended stretching or pain relief interventions.

Perhaps most telling were lab-based saddle pressure maps conducted mid-experiment. These showed more even distribution across the sit bones and significantly lower peak pressures in the perineal region, correlating strongly with the absence of saddle sores. Subjective ride enjoyment also rose—scoring 8/10 compared to a baseline of 6/10.

📈 6. Performance Metrics Remained Solid

Despite initial concerns that the reduction in crank length might impair high-torque power delivery, test results showed otherwise. The rider maintained peak 5-second power (~1,400 W), and his time on the control climb (3.6 km at 8.7%) remained within 1.5% of his personal record. Power consistency across rolling terrain also improved slightly, potentially due to the higher average cadence and smoother pedal stroke.

Normalized power and average heart rate remained consistent, validating that cardiovascular load was unaffected. This supports prior research that suggests crank length has a negligible impact on power production, so long as gearing and cadence are adjusted appropriately.

📉 7. Situations Where Long Cranks Still Help

Despite the overall success of the shorter crank experiment, the rider acknowledged a few scenarios where longer cranks may still provide an edge—particularly in mass-start sprint finishes and rough terrain. During races like the cobbled classics of Northern Europe, where low-cadence torque and out-of-the-saddle sprints dominate, longer cranks might offer a marginal mechanical advantage.

Moreover, regulatory constraints (such as UCI’s rules on saddle placement) and equipment limitations mean that not all riders can easily switch to ultra-short cranks. Many standard cranksets bottom out at 165 mm, and pro sponsorship agreements often limit experimentation with unconventional components.

📚 8. Scientific Validation

The findings from this real-world test align well with published literature on crank biomechanics. Peer-reviewed studies confirm that crank length has minimal effect on power output when gearing is normalized. However, joint angles—particularly at the knee and hip—are markedly improved with shorter cranks, leading to reduced strain and greater long-term joint health.

In particular, research on arterial dynamics shows that reducing hip flexion improves blood flow consistency during endurance efforts, supporting the vascular efficiency claims made by Dr. Fonda. These insights reinforce the idea that shorter cranks aren’t just a comfort tweak—they represent a performance-enhancing adjustment with physiological implications.

🧪 9. What’s Next?

Encouraged by the results, the rider plans to expand the experiment to even shorter crank lengths—160 mm and potentially 155 mm—to assess whether the gains in comfort and hip mobility can be further enhanced without compromising performance. Additionally, controlled lab testing is being considered to explore the effects of crank length on sprint acceleration, time-trialing efficiency, and cyclocross handling.

A long-term study is also being devised to track injury incidence and joint inflammation metrics over multiple training seasons. If shorter cranks contribute to reduced rates of overuse injuries, they could play a major role in athletic longevity—especially among aging cyclists or those prone to hip and back issues.

✅ 10. Final Thoughts

This 30-day, 1,000 km experiment not only validated the practical use of 165 mm cranks for tall riders but also demonstrated that modern bike fitting should prioritize comfort, efficiency, and biomechanics over tradition. For cyclists dealing with chronic pain, limited flexibility, or poor aerodynamics, shorter cranks offer a transformative solution backed by data and experience.

The takeaway is clear: personalized bike fitting—particularly crank length optimization—has the power to change how we ride, train, and recover. The rider has now transitioned all personal bikes to 165 mm cranks and encourages others to challenge convention with thoughtful, evidence-based experimentation.

References:
absoluteBLACK Science Lab (Dr. Borut Fonda)
FSA K-Force Team Edition specs
Zwift Ride Smart Bike configurations
Peer-reviewed studies on biomechanics