Just make sure to lower the seat 5mm when you put the new cranks on, or it's not really a fair trial.
my experience with crank length is that confirmation bias dominates. I usually ride 170mm cranks. I first tried 172.5 cranks decades ago, and thought they slowed me down. 2.5mm is a tiny difference. About that same time, I got some 165mm cranks for my commuter and couldn't really tell the difference. Years later, I bought a set of 172.5 cranks assuming they were 170mm cranks, and I couldn't tell. Then I started riding 175mm cranks on mtb and my gravel bike and couldn't really feel any difference. 5mm is about the difference in seat height where I can tell if the seat is too high or low, so I feel like that's the big difference with cranks for me.
Toe overlap makes a bike designer's life problematic. You can push the seat tube forward and go slack head tube/long rake, or try to talk the person into smaller wheels. And then people discovered that having cleats further back is better. Whoops. I hit my fenders with my foot all the time. It's always a bit of a surprise, but I'm mostly worried about the fenders.
In a bit of a over-broad generalization, I think randonneurs tend to spin too slow. I know I do. And I need to lower my seat and possibly move it forward a bit.
Last edited by unterhausen; 03-28-19 at 08:16 AM.