I just changed from a 175 to a 165 crank length. My reason was knee pain and it has helped as the angle of my knee at the top of the stroke is less. It has given me the impression that I have lost speed but my Wahoo does not substantiate that. For me, at 72, speed is not as much of a concern as comfort. I also was able to remove the peddle spacers, known as knee savers in some ads, as my legs now stay over my foot on the downstroke. Again, just my situation and what works for me but it has given me the desired result and that is what I was hoping for. As for the rear cogs, I had changed them from the 11-34 to 11-36 before the crank swap. A lot of hills here and needed help on the low end.
Good luck, Frank.
