Pros and Cons of Crank Length 170 vs 175

Discussion in 'Cycling Equipment' started by Tom, Mar 7, 2004.

  1. Tom

    Tom Guest

    The subject pretty well says it. Which is easier in the
    mountains and/or on the flats, etc. What is preferred on a
    'racer' versus a 'touring' bike? Is the difference really
    noticeable?

    Tom
     
    Tags:


  2. "Tom" wrote:
    > The subject pretty well says it. Which is easier in the
    > mountains and/or on the flats, etc. What is preferred on a
    > 'racer' versus a 'touring'
    bike?
    > Is the difference really noticeable?

    A longer crank requires slightly less pedal force for a
    given gear, but your feet trace a slightly wider circle.
    Generally, tall riders and/or big gear mashers prefer longer
    cranks. Shorter riders or those who like to maintain a high
    cadence tend to prefer shorter cranks.

    Cranks can be a short as 165 mm, or as long as 180 mm
    or greater.

    If can't decide between 170 and 175 mm, you might want
    get 172.5 mm. It's doubtful that you'll notice a 2.5 mm
    either way.

    Art Harris
     
  3. Mseries

    Mseries Guest

    Arthur Harris wrote:
    > "Tom" wrote:
    >> The subject pretty well says it. Which is easier in the
    >> mountains and/or on the flats, etc. What is preferred on
    >> a 'racer' versus a 'touring' bike? Is the difference
    >> really noticeable?
    >
    > A longer crank requires slightly less pedal force for a
    > given gear, but your feet trace a slightly wider circle.
    > Generally, tall riders and/or big gear mashers prefer
    > longer cranks. Shorter riders or those who like to
    > maintain a high cadence tend to prefer shorter cranks.
    >
    > Cranks can be a short as 165 mm, or as long as 180 mm or
    > greater.
    >
    > If can't decide between 170 and 175 mm, you might want
    > get 172.5 mm. It's doubtful that you'll notice a 2.5 mm
    > either way.
    >
    > Art Harris

    I switched cranks on a bike mid-tour from 170 to 172.5 mm,
    didn't notice any difference.

    --
    The Reply & From email addresses are checked rarely.
    http://www.mseries.freeserve.co.uk
     
  4. Tom wrote:

    > The subject pretty well says it. Which is easier in the
    > mountains and/or on the flats, etc. What is preferred on a
    > 'racer' versus a 'touring' bike? Is the difference really
    > noticeable?

    I have 165s on the road bikes, but the MTB has 175s because
    shorter cranks are very hard to find at a sensible price.

    The 165s are easier if you're a 100rpm twiddler like I am.
    The 175s can't be spun as smoothly but feel a bit better at
    low revs. Given the relatively shorter distances I ride the
    MTB, I can live with the difference.

    Note that you need to drop your saddle slightly if you
    change to longer cranks, to avoid over-extending the
    knee. My saddle height (top of saddle to centre of BB) is
    30" on the road bikes, but only 29.5" on the MTB. If you
    usually set the bike up by trial and error and don't have
    a known preference worked out over several years, this
    isn't an issue!
     
  5. Carl Fogel

    Carl Fogel Guest

    "Tom" <tomhob(nospam)@overland.net> wrote in message news:<[email protected]>...
    > The subject pretty well says it. Which is easier in the
    > mountains and/or on the flats, etc. What is preferred on a
    > 'racer' versus a 'touring' bike? Is the difference really
    > noticeable?
    >
    > Tom

    Dear Tom,

    Longer cranks offer slightly lower overall gearing. Your
    feet still rotate at the same RPM for a given speed, but
    describe a slightly larger circle, spreading the force out
    over a greater distance. (The ratio is 175 to 170, around
    3%, while switching from a 52 to a 53 tooth sprocket changes
    gearing about 2%.)

    The slightly larger circle might or might not bother your
    knees, dig a pedal into the ground a little sooner in a
    corner, or let your toes hit the back of the front tire.

    Comfort is what most people worry about when they think
    about crank size.

    Before getting excited, remember that 5 mm is just under a
    fifth of an inch. (Some riders have written that they can
    feel an uncomfortable difference between thin and thick
    socks, but there is some doubt whether such claims would
    survive double-blind testing.)

    A possible explanation for people finding great benefits in
    crank changes as small as 2.5 mm is that, for example, they
    would have been happiest with 170.0 mm cranks, were using
    172.5 mm cranks on the borderline of discomfort, tried to
    use 175.0 mm cranks, and found themselves two shoe-sizes too
    large, to use an analogy.

    Longer-legged riders tend to like larger cranks.

    Carl Fogel
     
  6. On my MTB that I also ride for trials, I switched out a
    175mm set with a 170mm set and immediately noticed the
    difference on the first ride. The difference quickly
    went away and I believe for my short legs, the 170 is
    better for me.

    I also have 170s on my road bike... the pedal clearance is
    so ridiculously low already, I'd probably crash a lot more
    if I switched to 175s. (Yes, I keep inboard-pedal-up in
    turns, but giving power in turns surprises me...)

    My freeride bike has 175s, but it tends to need the torque
    because it's ~40lbs.

    Phil

    "Tom" <tomhob(nospam)@overland.net> wrote in message news:[email protected]
    berlin.de...
    > The subject pretty well says it. Which is easier in the
    > mountains and/or on the flats, etc. What is preferred on a
    > 'racer' versus a 'touring'
    bike?
    > Is the difference really noticeable?
    >
    > Tom
     
  7. Mike S.

    Mike S. Guest

    > Before getting excited, remember that 5 mm is just under a
    > fifth of an inch. (Some riders have written that they can
    > feel an uncomfortable difference between thin and thick
    > socks, but there is some doubt whether such claims would
    > survive double-blind testing.)

    Tell that to my legs!

    >
    > A possible explanation for people finding great benefits
    > in crank changes as small as 2.5 mm is that, for example,
    > they would have been happiest with 170.0 mm cranks, were
    > using 172.5 mm cranks on the borderline of discomfort,
    > tried to use 175.0 mm cranks, and found themselves two shoe-
    > sizes too large, to use an analogy.
    >
    > Longer-legged riders tend to like larger cranks.
    >
    > Carl Fogel
     
Loading...
Loading...