The psychological element to cycling is undeniable and therefore real even if unsupported by physics.
Maybe introduce a bit of science. Too bad you don't invest in a Stages powermeter with your new R8000 crank to quantify any 'perceived' difference.

Btw, I ride 175mm cranks but don't believe I would be much slower if any on 172 mm...perhaps the opposite.

What is your cycling inseam?

Many years ago before the great Sheldon Brown died unexpectedly I emailed him several questions about cycling. He was very gracious to respond. I asked him about crank length affecting power and speed on the bike and his response was crank length makes no different at all when it comes to how fast a rider is. We were about the same height with similar inseam and he owned bikes with cranks from 175 to well into the 160's. Of course it may for example affect the balance of the rider on the bike. KOPS is different for example with the same saddle position and we do control balance on a bicycle by our feet which is our platform and why saddle setback matters.


Probably most of perception is your head but don't believe many would argue that there maybe a discernible 'feel' difference...but not likely a great deal of difference in actual speed on the bike.