You are reading a single comment by @gbj_tester and its replies.
Click here to read the full conversation.
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
@gbj_tester
I expect we're both looking at the same few research papers and drawing different conclusions from the combined results. The maximal power and metabolic cost results show a pretty flat graph for medium length cranks (a wider range than the 165-180 normally available) which makes me say crank length doesn't matter, while they show some variance at extreme crank lengths (120mm and 220mm) which makes you say crank length matters.
My own n=1 tests show that 10 mile TT time on a fixed course is unchanged if crank length is changed from 175mm to 140mm while keeping gain ratio constant and making no other changes to the bicycle. Obvious weaknesses in those tests include lack of control, lack of proper instrumentation and very different adaptation times for the two lengths tested, i.e. 30 years on 175s vs. a week on 140s. However, the results were so close (just a few seconds) and so out of proportion to the variability caused by changing gain ratio that it didn't seem worth pursuing when there were plenty of more substantial gains to chase.
On TT bikes where hip angle closure can limit the torso angle, some people might find short cranks a benefit, although it seems that most of us can get as low as we need to without resorting to such measures. That's an aerodynamic question rather than a biomechanical one. As I pointed out way up thread, not many people are compromised by hip angle closure when riding a normal road/track bike on the drops.
As I also pointed out, the science is both sparse and, in terms of recent rapid progress in bicycle science, old. However, in the decade since Martin & Spirduso, several very well funded teams have aggressively chased marginal gains, yet we still see all elite competitors using the same narrow range of crank lengths which have been used almost since the introduction of non-unity relation between crank speed and wheel speed, even for athletes of widely ranging size.