Note: the previous was written in a rush after a really good ride. I have toned down things a bit since then...
I'm not trying to start a crank war, but I needed to get a somewhat strange experience off my chest.
I went for a ride today: a fairly short, one-hour tour with some nice climbing. It had a bit of road (icy asphalt, most of the time, considering the light snowfall and subsequent freezing temperatures of the past few days) and some snowy singletrack.
Normally, I'd be riding my trusty On One Inbred, equipped with 2.2 (rear) and 2.4 (front) tyres, platform pedals, 195mm cranks, 33:21 gearing and Jones H-Bar. A beast, so to speak.
Today, however, I had been tinkering in my garage with my On One Il Pompino frame. I'd built it up with 35c Schwalbe Marathon tyres (slick ones), platform pedals, 170mm cranks, 32:16 gearing and my old Azonic Double Wall Riser plus bar ends.
Over the past few years, I've read just about anything I could get my hands on concerning crank length. I've got a 37” (94cm) inseam, and the 195mm cranks are just about proportional to me. I've been riding them for about half a year now and I like them. (So far, I've run everything from 165s up to the current 195s.)
Imagine my surprise today when the Pompino flew. Of course, the tyres (and bike) are lighter than my Inbred, but they were inflated for road duty. It made the ride pretty harsh, but it was harsh in a bouncy, skippy way.
The biggest surprise, though, came from the cranks (a cheap, second-hand set of Shimano Alivio, by the way). The 32:16 gearing was a bit much, obviously, but I was astonished at the ease with which I could keep pedalling in rough terrain. Because the motion of my legs and hips was much less pronounced, I seemed able to keep the whole thing together much more easily. My core muscles were less 'disturbed', as it were, and could concentrate on keeping everything tight.
For the same reason, I seemed better able to deal with shocks transmitted through the bike.
Another element was climbing: I don't know if I lost a lot of leverage (physics would say yes, I guess), but with the shorter cranks I didn't 'sink' as deep down, nor did I have to 'lift' myself as high up. I know that being 'in' the bike is a nice feeling when riding seated, but when you're doing standing climbs (a major element in singlespeeding, as we can no doubt all agree), I like to feel 'on top' of the bike.
All in all, the word I'd use to describe the impression the 170s gave me, is efficient.
For what it's worth, I quickly hopped onto the bike with the 195s as soon as I got back, just to get the 'feel'. It was odd, but not as odd as one may think.
I have to say that I'm somewhat at a loss. I thought I'd just about figured everything out about bike fit (proportional cranks: yes please! - thank you Sparty, Shiggy et al.), but now I'm leaning towards the 'shorter than recommended for your inseam' again (the Matt Chester approach, as it were).