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  1. #1
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    crank arm length

    So most likely I'll be picking up a new 2013 Langster Pro from the lbs and it comes with 167.5mm crank arm length but I normally use 165mm cranks. Should I switch to 165mm or give the 167.5mm cranks a try?
    http://www.pedalroom.com/bike/unknown-psx--16196

  2. #2
    Elitist carleton's Avatar
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    Quote Originally Posted by sbs z31 View Post
    So most likely I'll be picking up a new 2013 Langster Pro from the lbs...
    Did you take pics of you on the bike? You don't want to buy a 3rd bike that is too small

    Quote Originally Posted by sbs z31 View Post
    ...it comes with 167.5mm crank arm length but I normally use 165mm cranks. Should I switch to 165mm or give the 167.5mm cranks a try?

    Crank arm length is a personal thing with very even pros and cons.

    Here are the rule's of thumb:

    - Shorter riders use 165mm
    - Medium riders use 167.5mm
    - Tall riders use 170mm

    These are great starting points.

    Shorter than normal cranks allow one to carry higher cadences easier, but making torque is harder because the lever (crank arm) is shorter. Longer than normal cranks allow for easier creation of torque (longer lever) but carrying higher cadences is harder. Personally, for beginners, I'd err on the side of higher cadences as track racing involves higher cadences than they expect. Many people on the road average around 70-80RPM then when sprints happen, they just switch to harder gears and keep that 70-80RPM...maybe up to 90-100. On the track, beginner racing cadences start at 100RPM and go up to 120-130 or so. More than they are used to.

    After training/racing for a while, people may want to fine tune. Please do not try to fine tune BEFORE you ever race. You can't research your way into the perfect crank/gearing setup. You just have to put your body on the bike and see what happens.

    Adjust for events, gearing, and/or riding style:

    - If you like to spin fast go down 2.5mm.
    - If you like to grind big gears go up 2.5mm.
    - If you do a bit of both, stay put.
    - If you ride bigger gears go longer.
    - If you ride smaller gears go shorter.


    To be honest, it won't really matter for beginner racers as there are so many other factors that will have a MUCH bigger effect than crank length. Think of it like an amateur auto racer debating wether to use 98 or 100 Octane fuel in their lightly modified Honda Civic beginner race car. It's not going to matter much. But, later on, when that racer is winning or losing by tenths of a second, then it may be a factor (still not a major one).

  3. #3
    Senior Member Impreza_aL's Avatar
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    i raced all year last year using 165mm but i moved to 170mm to match my road bike. i already raced on them a couple weeks ago. i didn't notice a difference. then again i've only been riding/racing for a year

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    Elitist carleton's Avatar
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    Quote Originally Posted by Impreza_aL View Post
    i raced all year last year using 165mm but i moved to 170mm to match my road bike. i already raced on them a couple weeks ago. i didn't notice a difference. then again i've only been riding/racing for a year
    Oh yeah... and there is that factor.

    Some people are like The Princess and the Pea and can feel minute changes and others, amazingly, cannot. It's good to not be sensitive to such things that way you are less finicky.

    I've raced 165s, 167.5s, and 170s, and didn't see a significant change in my actual times. There were big changes in my gear choices and cadences, but no big changes in my standing lap, 500M, Kilo, or Flying 200M times. The changes that did occur over the year can be attributed to other factors.

  5. #5
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    I noticed a bit of difference going from 165 to 170 (I ride 175 on road but our track 'dislikes' long cranks), but it wasn't huge and I can't say it had an effect on my times that I could notice. I change gearing a lot though so its very possible I prefer a bigger gear now and a lower cadence, but I can't blame that 100% on the crank length.

    I completely agree with the above, you cannot research your way to a correct answer. IMO, and it may be disagreed with, crank length makes very little difference to the majority of people (talking 2.5-5mm changes, not 160s vs 180s).

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