I too have a 36” inseam. I’ve had 6 professional bike fittings over the years (retul, guru, slowman) and every single one of them put me on 175mm cranks - both road bike and tri bike. Am I missing out on power? Dunno. But I figure I should follow their expertise and then seek additional power via other training means. YMMV.

Reasonable crank length has zero effect on submaximal power... this is one of the few stone cold lead pipe locks in physiology.

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I've tried 170-177.5 and no power difference between them. I ride 170s on my TT bike for hip angle, might try 165s this year....if there is any racing that is.

So, if you're not running OTB, why go shorter? Is this an injury prevention thing?

You're damn strong, and tall, and have proven you can manage crank length at the far end of normal range. Why go short? (Yeah, I realize it's just a few mm shorter, so not a big deal, just curious).

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Can you define reasonable and sub max?
I’m talking about 5 minute Vo2max efforts, are these what you’re including.

The shorter the crank the less closed off your hips are. Problem is you have to raise your saddle when you shorten the arms, so you can lose aero.

Well, if you are taking fit totally out of the equation here is what you have left:

The combination of force and cadence required to achieve your target power and how that relates to your physiological preferences. This is probably best just evaluated by feel over time.

With equal force applied to the pedals, shorter cranks require higher rpm to get the same power. But assuming equal force applied to the pedals may not be right. In reality there are many many variables.

But these small changes in force and cadence are typically easily adapted to within the reasonable range of crank lengths and after a short time you will not notice a difference.

Therefore I think fit is by far a more important factor, even in an upright position on a trainer. Sounds like hip angle is not a concern for you even with the long crank so that gives you the option of going long if it feels better for you. But I don't think you will find major power differences either way, after a suitable period of getting used to it.

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I'm 6'3" with a 36" (maybe 36.5") inseam and I'm running 165s on the TT after starting off on 172.5s. Morphology wise, which I think is important here, I think I have longer lower legs/arms vs upper (so, better running morphology than cycling). I'm not very flexible, and my running gait is higher cadence ~180 with shorter strides - I look like I'm barely trying when I'm running hard in terms of hip extension and leg lift. That all being said, for me, the move to 165s was a massive benefit. It allowed me to drop the front end, and I just feel much more comfortable putting out power over a shorter arc like this. I feel like I run better off the bike as well. My guess is that a lot of the benefit of shorter cranks comes during long efforts as you're just using less range of motion (which explains the run). I went from 175s to 170s on my road bike and I actually regret not going to 165s there as well. That being said, if you're flexible and comfortable at the longer cranks, going shorter is probably very minimal gains (or even losses). Perhaps if you skew toward longer upper legs (femurs), that changes the equation a bit.

Yes, that's in the range. Plenty of studies on 120mm-200mm. If you're an elite BMX rider in the Olympic final you might consider avoiding 140mm cranks but for us mortals it's just personal preference.

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

I pondered this question in a previous thread based on my experience of finding it easier to get more out of myself in a 20min flat out effort on the turbo when I used 200s instead of 170s. I feel there is some benefit, although it may be only one of perceived effort particularly when the legs are not rested.
Unfortunately most of the responses were, as you will have noticed, people saying they got a negligible change in power when they made a negligible change in length.
The "science" is also not as clear cut as some say, I could only find people answering different questions either about max power or about efficiency at very low power but would delighted to be proved wrong (as it would save me buying more super long cranks)

Can you point me to any studies on crank length conducted at FTP or similar?
I can only find Jim Martins work which uses submax (below lactate threshold) and maximal.

I agree and heres my theory behind this.

I personally have very long, but relatively weak legs. In that my muscles (particularly quads) are long but not thick, so the cross-sectional area (which largely explains the force generation of a muscle) is relatively low.

Not only are these longish legs not that strong they don't like moving too fast, or applying force too fast.

In this instance a longer crank will reduce the force required for the same torque, correct?
You could compensate for this with a shorter crank by increasing the RPM to arrive at the same power.
But what if you are already moving towards an RPM at the top of what you feel comfortable.

This brings me onto FTP, a mystical peak of sustained power that sits close enough to MLSS but is not really it. It has all elements playing into it, including physiology and psychology (why estimates are often wrong when they are short, this removes the psychological element of actually going the distance)

At FTP I think crank length could make a difference, to SOME people. I personally can ride at submax e.g. sweetspot with pretty much anything from 155-180, i've tested it.
But at FTP for an actual test e.g. 45 minutes up the alpe on Zwift I am far more comfortable, and put out at least 10-20 more watts at 172.5 than I do at 165. Could I acclimate with time? Yes I expect so. But for now longer feels better and results in more sustained power.

On the contrary to this, when fit is an issue (TT bike) I take the power hit and ride 165.

As an additional point, these 'weak but long legs' result in me finding it much harder in the slightest headwind. Yet I seem fine spinning at high power up a hill