how long should your legs be too consider trying a 172.5mm crank arm length?

Viewing 14 posts - 1 through 14 (of 14 total)
  • how long should your legs be too consider trying a 172.5mm crank arm length?
  • slimjim78
    Member

    I’m just over 6ft, but have really short inseam for my height at 31″

    Should I consider a 172.5mm crank arm? (on road bike if it makes any difference?).

    What perceivable difference will there be?
    Would I spin more efficiently?
    Would I lose power when grinding uphill?
    Could I perhaps find it more comfortable?

    I’ve never really gotten my head around the reasoning behind crank arm length.

    slimjim78
    Member

    whoosh..
    straight over my head

    iain1775
    Member

    I think there are generally 3 schools of thought with this one –

    1.
    None
    Yes
    No
    Maybe

    2.
    Lots
    No
    Maybe
    Yes

    3.
    A little, possibly
    Maybe
    Hard to tell
    Depends

    slimjim78
    Member

    I thought so

    Premier Icon cynic-al
    Subscriber

    if you believe you’ll notice a difference, you probably will.

    Junkyard
    Member

    What perceivable difference will there be? al oss of power but marginal 5 % ish
    Would I spin more efficiently? I doubt it – whayt do you mean by efficiently?
    Would I lose power when grinding uphill? see above
    Could I perhaps find it more comfortable? I assume you would higher the seat as pedal to seat remains 107% so not sure what you mean – higher your seat what do you think of this position?

    tape wooden blocks to some flats to make cranks the correct length and see what you think?

    Premier Icon scaredypants
    Subscriber

    What are they currently ?
    road cranks are normally 172.5 aren’t they ?

    Premier Icon thisisnotaspoon
    Subscriber

    tape wooden blocks to some flats to make cranks the correct length and see what you think?

    That’d just simulate a high BB.

    172.5 seems the standard for roadies, 170mm is for short arses and 175 for really tall people.

    Your saddle would be 2.5mm higher and 2.5mm further foreward, and your foor 5mm further foreward at the 9 o’clock position relative to your saddle. I’ve got 170mm cranks on one of my road bikes and 175 on the tourer, I think there’s a difference, but it might be in my head.

    dean0
    Member

    From my own experience, it matters less than you might think. My main bike has a low bb and I run it with 165mm cranks. I also have a full-sus with a slightly higher bb (but still low by most standards) with 175mm cranks (cos that’s what I always used to buy).

    I can’t say I can tell much difference, but then one bike is rigid SS and the other FS. The advantage, as far as I can tell, is fewer pedal strikes on a bike with a lower bb. I’m sure there are all sorts of leverage issues at play, but I can’t say it makes a discernable difference (to me).

    I’m a touch shorter than you with a much longer inseam btw (over 35″).

    Some time ago I bought a Trek road bike. After 3-4 years of riding it I discovered that the left crank was a 172.5 & the right was 170. Never ever noticed the difference when riding it 😀

    PJM1974
    Member

    I’ve a set of 170mm SLX cranks on the AM bike, which I inadvertently bought and a set of 175 SLX cranks on my XC bike. Differences?

    Aside from the shorter cranks having a double and bash, none that I can detect at the pedals.

    Junkyard
    Member

    That’d just simulate a high BB

    no it would effectively make the crank short at the bottom and tall at the top like having two different crank lengths.

Viewing 14 posts - 1 through 14 (of 14 total)

The topic ‘how long should your legs be too consider trying a 172.5mm crank arm length?’ is closed to new replies.