Crank length.

Discussion in 'Bicycle Mechanics and Repairs' started by Saddle bum, 14 Jun 2008.

  1. Saddle bum

    Saddle bum Über Member

    I used to ride 172.5 cranks in the early 90s, but settled for 170s when I got a new iron a few years back. I've just upgraded again to 172.5s, it makes a big difference, a positive one.

    Any similar experiences?
  2. Mister Paul

    Mister Paul Legendary Member

    Crank length is something that I've never even thought about, let alone played with.
  3. Night Train

    Night Train Maker of Things

    Greater Manchester
    I've never considered crank length either. How do you work out what length you need?
  4. gavintc

    gavintc Guru

    There are ratios based on leg length. Google for it. I fitted 175mm following my research a couple of years ago.
  5. Steve Austin

    Steve Austin The Marmalade Kid

    Lots of theories on this, most of them complete conkers.

    long legs = long cranks. Its that simple

    I use 175 on my Roadbikes and MTBs as it feels very different when changing bikes. And i've got long legs :smile:
  6. piedwagtail91

    piedwagtail91 Über Member

    a clubmate had his best ever racing season using different length cranks(by accident) he didn't realise until mid season but was going so well didn't want to risk changing them.
    i had to use odd length cranks in our clubs 150 mile ride. the spider came loose on the crank so i had to put a spare on which was a different length, after a couple of miles i couldn't tell the was only 2.5 mm.
    I've different lengths on all 3 bikes but haven't found much difference. clumbates swear the can and will only use certain lengths.
    i buy what is going cheap in the sale which explains the differences!
  7. OP
    Saddle bum

    Saddle bum Über Member

    On the wild assumption that many years ago, Britain set certain standards in bicycle technology, 6-3/4-in was the standard crank length. This translates to 171.4mm. So 170s are shorter than the old fashioned standard.

    I would propose that 172.5 should be the norm for any male person of 5ft 8in high or over. Different reasoning may apply to the ladies, with certain notable exceptions, I am not an expert on female physiology.
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