Originally Posted by
PeteHski
Cadence and load is more a function of gearing than crank length. Shorter cranks will naturally increase your cadence in a particular gear (pedalling a shorter circumference), but shifting even one gear will more than compensate for the difference.
The only thing to consider with crank length is your preferred range of leg motion. I know of 2 very experienced fitters who both generally favour shorter cranks, especially if you are of average height or less and/or have limited joint flexibility.
One of them published a review of crank length based on various previous studies (some conflicting) and his own fitting experience with hundreds of clients. The bottom line was to go shorter when in any doubt. While there are various potential issues with longer cranks, there are very few with shorter cranks.
My personal experience is that I can’t tell any significant difference between 170, 172.5 and 175 mm cranks. I’m 6’ tall with relatively long legs.
I've read quote a bit that we lose flexibility/mobility as we age and that reducing the length of the crank is generally a good idea as we get older. I'm not exactly ancient at 46 and have decent flexibility. I've read a lot and watched the bike fit guys videos and they echoed what you said in your post; that there are almost no disadvantages to going down a bit in crank length. I'm not racing or chasing grams so pretty much everything my bike is designed around is comfort and injury prevention. Performance comes second. My bike will go as fast and as far as my mind and body will push it, but not at the risk of injury or pain. That's how I look at it.
The main concern I had was will I lose the ability to climb as well. I live in very hilly area and that would not be good. However, from what I've been able to gather, the research suggests there is a very minimal power loss if any at all.