The crank length conversation has shifted faster at the World Tour than it has at the amateur club level, and the gap is now wide enough to be worth closing. Most amateur road bikes ship with 172.5 or 175 mm cranks as the industry default. Most professional bikes — and most current British Cycling track bikes — sit at 165 mm or shorter. The performance gap implied by the difference is one of the largest non-marginal gains still available to the serious amateur, and it is a one-time equipment change rather than a multi-week training block.
The conversation Anthony Walsh has been running on the Roadman Cycling Podcast pulls together the Phil Burt data, the Bradley Wiggins case study, the Pogacar and Vingegaard adoption, and the practical bike fit changes required to make the switch correctly. The episode is the cleanest single-session education on the topic in cycling content.
Listen to the full crank length episode →
This piece walks through what the data shows, what the pros are doing, and what amateurs need to change about their bike fit to make the switch work.
Where The Number Comes From
The 15-watt FTP claim is not a marketing line. It comes from Phil Burt — the former British Cycling and Ineos physiotherapist who has spent the last fifteen years working through the bike fit data on the riders who were already riding the fastest bikes in the world. Burt's appearance on the Roadman Cycling Podcast is the foundational conversation in the Roadman archive on crank length, and the data he presented on British Cycling track riders moving from 172.5 mm cranks to 165 mm or shorter showed an average gain in the region of 15 watts of FTP.
That number is significant in context. A focused multi-week training block — well-prescribed, well-recovered, well-executed — typically produces 5 to 15 watts of FTP gain in a trained amateur. The crank length change produces a similar gain as a one-time equipment intervention. The training cost is zero. The bike fit cost is one professional fit session and the price of a new crankset.
The mechanism is well-characterised. Shorter cranks reduce the depth of hip flexion at the top of the pedal stroke. The hip joint sits in a more open angle. The hip flexors do less work clearing the top of the stroke. The diaphragm has more room because the chest cavity is not closed off by extreme hip flexion. Three downstream effects follow. The pedalling efficiency improves because the muscular cost of clearing dead spot is lower. The breathing is deeper and easier in aerodynamic positions because the chest is not compressed. The aero position can be more aggressive without compromising the rider's ability to produce power.
The combined effect — efficiency, breathing, and aerodynamics — adds up to the 15-watt figure. None of the three contributions is dominant. They stack.
The Wiggins Case Study
The aerodynamic component on its own is large enough to justify the change for any rider who races against a clock. The clearest published case study is Bradley Wiggins's time trial position adjustment. Wiggins moved from 177 mm to 170 mm cranks — a 2.5 mm reduction smaller than what most amateurs are now considering — and the change dropped his front end by 30 mm. The lower front end improved his total aerodynamic profile by 3.5 per cent.
For a rider averaging 50 km/h on a flat time trial, a 3.5 per cent aerodynamic improvement is roughly a 30-watt saving at the same speed, or roughly 1 km/h faster at the same power. The numbers are large enough that the change paid for itself the first time Wiggins raced against a clock after making it.
For amateurs racing time trials or triathlons, the same logic applies. The hip angle change unlocks a lower, more aerodynamic upper body position. The lower position cuts drag. The drag reduction is sustained across the entire ride. The compounding effect over a 40 km time trial or a 90 km triathlon bike leg is significant.
For the broader aero versus weight conversation that sits underneath this, see the aero vs weight piece and the aero position training piece.
The Pro Adoption Signal
The professional adoption of shorter cranks is now extensive enough that it functions as its own evidence base. Tadej Pogacar has been on shorter cranks for several seasons. The exact length is not always public, but the photographic evidence shows a noticeably shorter crank than the industry default.
Jonas Vingegaard's case is more telling. In 2025, photographs surfaced of Vingegaard's cranks with the manufacturer length markings filed off. The Visma-Lease A Bike team had visibly removed the size information. The competitive sensitivity is itself confirmation that the team considers the crank length to be a meaningful gain — not the kind of detail you hide if it does not matter.
Below the top of the sport, the diffusion through the World Tour is essentially complete. The 165 mm and shorter cranks are now the default at most teams. The amateur market lag is years rather than months, primarily because the shorter cranks are not standard equipment on most off-the-shelf bikes and most riders never reconsider the cranks the bike came with.
The Bike Fit Change
The single most important practical detail Anthony emphasises on the podcast is that the cranks cannot be installed without changing the bike fit. The change is not a bolt-on swap. It is a position change.
Two adjustments are required.
Saddle height. Moves up by the difference in crank length. A change from 172.5 mm to 165 mm requires the saddle to rise by 7.5 mm. The reason is geometric — the pedal at the bottom of the stroke is now higher relative to the bottom bracket, and the leg extension at full reach has to be preserved. Without the saddle height adjustment, the rider's leg extension shortens and the pedalling efficiency drops.
Saddle fore-aft position. Moves slightly forward, typically 5 to 10 mm, to maintain knee position over the pedal axle. The forward shift compensates for the changed knee angle at the top of the stroke and preserves the rider's centre of gravity over the bottom bracket.
Failing to make these adjustments captures only a fraction of the gain and increases the risk of knee, hip, or lower back issues. The bike fit framing on the podcast is unambiguous — install shorter cranks with a professional bike fit, not as a Sunday afternoon garage project.
For a deeper treatment of the bike fit changes that matter most, see the bike fit one change amateurs should make piece.
What Cadence Does
Cadence naturally rises on shorter cranks. The mechanism is geometric — the pedal stroke circumference is smaller, and the same linear pedal velocity produces a higher rotation rate. A rider who currently averages 85 RPM on 172.5 mm cranks will typically settle into the high 80s or low 90s on 165 mm cranks without consciously trying to spin faster.
The effect is generally positive. Higher cadence at the same power reduces the per-pedal-stroke torque load, which is part of the joint stress reduction the shorter cranks provide. Riders who currently grind at low cadences — under 80 RPM — often find that shorter cranks naturally pull them into a more efficient cadence range without the deliberate cadence work that grinder-to-spinner transitions usually require.
For amateurs working through the cadence and torque relationship more deeply, the low cadence training and torque interval coverage on the broader podcast archive sits alongside this conversation.
The Cost-Benefit Calculation
The economics for an amateur are simple. A new crankset in the 165 mm length is typically $250 to $500 depending on the groupset. A professional bike fit to install correctly is $200 to $400. The total investment is in the $450 to $900 range.
The performance return — 15 watts of FTP, plus the aerodynamic gain for time trial-format racing, plus the comfort and joint stress reduction — is comparable in magnitude to a year of focused training in a structured plan. The investment pays back in performance terms within months for any amateur who races, races against the clock, or rides longer events where the aero and joint stress benefits compound.
The investment also pays back in injury reduction. The hip angle change reduces the load on the hip flexors and the lower back. Amateurs with persistent hip or lower back issues from cycling often find the shorter cranks resolve them within weeks. The injury avoidance alone justifies the change for many older riders.
What The Roadman Audience Should Take Away
Three things from the conversation translate directly to the serious amateur.
One. The 172.5 mm default is too long for most riders. The industry-standard crank length is a historical artefact, not an evidence-based recommendation. Most amateurs will benefit from moving to 165 mm or shorter. The professional consensus has converged on this position. The amateur market lag is the only reason the equipment has not changed yet.
Two. The change is a position change, not a parts swap. The cranks come off, the new cranks go on, and the bike fit changes — saddle up, saddle slightly forward, possibly a stem and bar height re-evaluation in light of the new hip angle. Install without the position change and the risk of injury rises while the gain falls.
Three. The economics work for any serious amateur. The investment is meaningful but the performance and comfort return is correspondingly large. For amateurs who race, the payback is in months. For amateurs riding long events, the comfort benefit alone is worth the cost.
For amateurs working through bike fit and equipment decisions, the Roadman coaching system is built to integrate equipment changes into a structured development plan. For a faster answer on a specific crank length or bike fit question, ask the AI coach.
Listen To The Full Conversation
The full episode — including the further questions on group ride etiquette, ERG mode, and the wider rider support discussion — is on the Roadman Cycling Podcast.
172.5 to 165. Saddle up by 7.5. Saddle forward by 5 to 10. Fifteen watts of FTP, a more aerodynamic position, and a hip joint that thanks you for it. The cycling industry will catch up to the change in due course. The amateurs who make the switch first capture the gain first.
