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Bike frame sizing -how to choose?

Discussion in 'Beginners' started by fizzy, 26 May 2008.

  1. fizzy

    fizzy New Member

    Hi there,

    I'm thinking of buying a 2007 Speciazled woman's Sirrus hybrid bike - will be doing an 11 mile commute on it, 2/3 times a week.

    I'm not sure what frame size I will need - I'm 157cm tall barefoot, and have a leg inseam of of 29 inches.

    Looking at the bike size guide for http://www.specialized.com/bc/SBCBkModel.jsp?spid=22267

    I can't work out whether I'd need a women's extra small or small?

    I will of course test the two but just wanted opinions on which one should ideally be right for me based on height and frame size.

    Or am I being too simplistic?

    Any thoughts gladly appreciated.

    Thanks ;)
     
  2. sheddy

    sheddy Veteran

    Location:
    Suffolk
    Fizzy, you need to see it in the bike shop and to ride it - do not buy mail order if you are new to this. Others will be along later regarding frame sizes....
     
  3. ASC1951

    ASC1951 Guru

    Location:
    Yorkshire
    The WS rather than the WXS, I would have thought, looking at their geometry table. Wait for an opinion from a woman, though.

    There are lots of sizing websites to give you more guidance. For instance,
    have a look at http://www.coloradocyclist.com/bikefit It does say "she fits her bike" etc

    There is no substitute for trying them both, as you say. The small adjustments for a perfect fit will come from saddle position and stem length, but a ride of a few miles should tell you which is the right size.
     
  4. OP
    OP
    fizzy

    fizzy New Member

    Thanks for this link Asc1951 - quick question do you think a hybrid would count as a road bike in this instance with regard to inseam measurements? For example in the article above they suggest multiplying inseam measurement by 0.67 for road bikes. Will this work for the sirrus...?
     
  5. OP
    OP
    fizzy

    fizzy New Member

    Thanks for the tip - I will be trying the two sizes later in the week. I'm just trying to do as much research as possible before I get in there as I'm really knew to this all.
     
  6. ASC1951

    ASC1951 Guru

    Location:
    Yorkshire
    More or less, fizzy. A hybrid gives you a more upright position and you aren't looking to extract the maximum power, so the fit isn't quite as critical as for a road bike.

    You can always adjust the saddle up and down, but the fore-and-aft movement is more limited, so the length of the top tube is actually more important than the length of the seat tube. Once you have used up the fore-and-aft movement you can only alter the stem length and that does affect the handling quite a lot.

    My best riding position (on drops) gives me a top tube length about 5% more than seat tube length assuming a horizontal frame. Women usually have shorter arms for their height, so that probably wouldn't be the same for you.

    For a lot of good sense on cycling for women (and not just women) do have a look at Myra VanInwegen's site. http://www.myra-simon.com/myra/bike/tips.html There is more useful information there than you will get from half a dozen bike shops.

    She also has a section on exactly the problem you are trying to solve.
    http://www.myra-simon.com/myra/bike/womens-fit.html