IME (40+ years of it), this is true. I'm 6'3", 37" inseam (long legs run in the family) and have settled on 175's, mostly because they work well for my pedaling style (high rpms) and are easy to find. I've tried everything from 160's to 180's on a variety of bikes, both conventional and recumbent and never found a noticeable performance difference. (I'm not riding 'bents any more but settled on 170's there.)

As with anything, ride what ya like and like what ya ride.

SP
OC, OR

There you define your needs , you want high cadence spinning, I don't..

According to that formula, my "number" is: 153.

I've used cranks from 155mm to 175mm. My own preference and best comfort is in the 155-165mm range. Current bike is at 170mm.

Have been eyeing the Thorn Short Triple crankset (which goes down as low as 150mm for the arms).

Haven't measured efficiency and power differences.

Here is a pretty good article/discussion about crank length I read a couple weeks ago that talks about all the formulas and the positives and negatives of each one-
Steve Hoggs - Crank Fitting, Which One?

-Sean

from this I should be using 165mm instead of the 175 that came on both my bikes ( gravel and road ).




https://bikedynamics.co.uk/FitGuidecranks.htm


Has anyone been professional fitted and have they tell you to use a shorter crank?

Most of my rides are in the 20 mile range. Longest 45/50 ish. Before I attempt todo a century I would like to get the bike dialed in more.

Myself, from a height standpoint I'm right about a 165mm arm, according to that chart, but I've got fairly short legs to cope with.

Had a fitting a few years back where 160-165mm was suggested. Could get away with 155-160mm. 170mm's a stretch.

Did you notice much of difference on your longer rides ( 3+ hours etc.. ) ?

Have only been on a couple 3hr+ rides, and that was decades ago. Mostly I'm a <90mins rider (old injuries preclude much time in the saddle). So, other than with 170mm or 175mm cranks, I've not had experience with much longer rides; but for relatively shorter times, <165mm feels better for me.

When I first switched from 175 to 170s it felt like I was riding a different bike... and no more anterior knee irritation on longer rides :-)

I recently watched a video on the tube that discussed the relationship between the crank length and the top of the peddle travel. According to the bike fit guy the angle of the knee at the top of the stroke is important to the power you can safely produce without causing an issue in the knee. I am 5'7" with a long torso and short legs so I will be looking into the validity of the crank length soon. I am going to change the BB and crank as soon as I can figure out what I need. My knees are starting to tell me they are not happy and I am not sure what direction I should go in if any. At 71 there are a lot of other things in play.
Be safe all, Frank.

At 178cm (a hair over 5 ft 10) and 83.5cm inseam, I feel better on 170mm cranks than on 175mm.

And you gotta be able to spin a lot faster to get the same power with the same pedal force that you'd use with longer cranks.- the same force at that higher cadence. It's true that aero does trump power to some extent. Big Mig rode higher than many because he could develop enough more power to go faster, but everyone's different.

I'm 5'11.5" and have been having great fun with Promax 135mm cranks. Hips were so far open at 190rpms, I opted to stop using them altogether

That's a photo that has interested me. We can see that the rider is a bit blurred, we can't see the spokes at all, yet we can clearly see his cranks and pedals. Of course the problem with that position is how to get one's feet back in the pedals. This photo suggests, IMO, that the cranks were somehow immobilized for this stunt.

Has anyone ever tried this? The saddle is extremely uncomfortable. Large, hard foam pad there? Good lower back musculature for sure. Kudos on that. The aero helmet combined with the sandals and inappropriate other attire is way over the top, though. Rather spoils it, IMO.