Some crank length experiments

I'm a tall guy but most of my length is in my body. My legs are comparatively short for someone my height. Which, for the purposes of this entry, means that cranks as short as 180mm have been OK for me. Really tall people are basically ignored by the bike industry.

After my Cannondale revelation, I swapped my road bike to Dura Ace 180mm cranks. And the next road bike I purchased, also had DA 180mm cranks. I moved the gear from the Cannondale to a Norco and built up a new Cannondale - so both bikes had 180mm cranks.
My first track bike was also a Cannondale. As a commercially available bike I assumed it was designed around 165mm cranks. I was wrong - but I didn't learn that until after I sold it! So I used 165mm cranks on it and hated them. They felt so short. I got a custom Ti track bike and boosted the bottom bracket height 15mm so I could use 180mm cranks on the track. It turned out to be too high because the Cannondale was high to begin with - they were going after the trendy courier market with the track bike and it needed a high bottom bracket to run fixie on the road.
All subsequent road and mountain bikes were equipped with 180mm cranks.
Until I got a DH bike. That had 165mm cranks. Even with short cranks it still had a lot of pedal strikes. DH bikes run really low, for stability, and pedalling one is a learned skill beyond pedalling in general.
My first trail bike - a Yeti - also got 180mm cranks on it. I thought it would be best for pedalling. Well on good climbs it was the best. But on janky climbs, or deep ruts, or descending, I often got pedal strike. On one stage in the Trans NZ Enduro, I had to scoot like a child on a run bike because my pedals hit the edges of the rut we were all riding in to get to the next stage (while my partner on the same model Yeti but 170mm cranks just pedalled along).
When I bought the Slash I had the shop swap the cranks to 170mm from the spec'd 175mm for extra ground clearance. It was a good idea. I don't have pedal strike problems with the bike, but I do still hit the pedals a bit. Like a DH bike the bottom bracket is on the lower side - especially if the suspension is compressed. The wide-range gearing and the sorts of trails I typically ride on this bike mean that I've never felt the cranks were too short. I tend to go for a lower gear and a higher cadence in comparison to my habits on longer cranks.
Last year I put my new commuter bike together. It was meant to have 180mm Campagnolo Record cranks on it. I bought the cranks before I bought the bike! Campy cranks are very straight and as I documented in this forum before, the curvy stays and the straight cranks didn't play well together at all. At all! I ended up with SRAM Red cranks on it, and they only "just" fit. There is 2-3mm of clearance (only). Meaning I'd never get a Stages or similar power meter on the bike.
It also means I'm not running 180mm cranks because SRAM chooses not to produce them. They are 177.5mm - the longest ones Red offers. Many times they've felt too short. Which strikes me as odd considering the 170s on the Slash feel fine. As they are compact cranks as well, the gearing is necessarily lower as well. Working well with the smaller gear and higher cadence approach.

My newest bike, the Ibis, also has 170mm cranks on it. And so far I've not struck a pedal. I feel like I can pedal through most terrain and the pedals still float above the terrain. I also feel like I can climb fine as long as I keep my cadence up.

I've known people who ran difference length cranks on one side of the bike compared to the other and didn't even notice. I'm pretty sensitive to crank length changes, in contrast. But these clearly shorter cranks seem to be working well for me.