PT1029 wrote:A friend in our local CUK group has 170/172.5/175 mm cranks on his 3 bikes, says he doesn't notice any difference.
I am used to 170 mm cranks. When building up a mountain bike (which later morphed into a camping/poor tarmac tourer) in the 1990's I was told mountain biking, best use 175 mm cranks (a new thing then).
While I could use 175 mm cranks without issues, I just couldn't get on with them, as the saddle simply felt too low*, so I replaced them with 170 mm cranks, and found them much better (for me at least).
My 1996 Gary Fisher Aquila is a typically 90s mountain bike equipped with 175mm cranks, i frequently used it as an urban street machine. I never noticed any concern over crank length while using it around the hilly town where i used to live, but i think this is because the rides were fairly short; 2 miles into town, 1 or 2 miles ambling around and 2miles to get back home again = just 5 or 6 miles, and riding uphill felt nice to have the extra leverage of the longer cranks, and around the rest of these urban excursions the cadence is naturally a lot lower than typical out-of-town mile crunching type riding, plus much freewheeling downhill or in traffic conditions. In other words, on rides where cadence can be lower for reasons of town traffic and junctions, one is not going to experience any obvious problem with crank lengths being a bit too long.
So my Aquila is okay for urban trips, shopping, and socialising around the town, however since moving to a new countryside location i've found it unpleasant to ride over longer distances where one wants to exercise ones 'natural cadence' but feels uncomfortable when trying to do this with a longer crank length, the other problem is the straight handle bars which again are fine on short urban trips but on longer rides i prefer drops so i can vary my hand position - but that's another story
Still got the Aquila, maybe one day i'll change the chainset to one with a 170mm crank, and convert it to drops