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Crank length difference - how to compensate?

arlowoodarlowood Posts: 2,534
edited January 2012 in Workshop
Hi there

Picked up my new Trek Madone last weekend and have been putting in some miles over the last week to check it out and get the set-up just right.

Noticed today when I was cleaning the bike that Dura Ace chainset has 172.5mm cranks. My old Spesh is a 105 triple with 175mm cranks.

Although the riding I have done so far has been OK comfortwise, I have been fiddling with saddle height and fore/aft position to get to my idea of a perfect position.

Knowing now that the cranks are shorter than on my old bike - Is there a rule of thumb about saddle positioning or other adjustments depending on the length of the cranks?


  • sungodsungod Posts: 14,056
    if the cranks are 2.5mm shorter, raise the saddle 2.5mm - then you get the same maximum extension assuming the same saddle position wrt to the bb

    btw there's some comment on crank length here...
    my bike - faster than god's and twice as shiny
  • YossieYossie Posts: 2,600

    You're not going to notice - just leave it as it is and ride the thing.

  • bus_terbus_ter Posts: 337
    Yossie wrote:

    You're not going to notice - just leave it as it is and ride the thing.


    +1. I have bikes with 170, 172.5 and 175. Honestly can't tell the difference. Differences such as the saddle height, position and even shape of the saddle will make much more difference than the 2.5mm of the crank length!
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