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Bike sizing

Ed AddisEd Addis Posts: 6
edited May 2015 in Commuting general
I'm really struggling to decide what size bike my partner needs. I'm buying online, so she can't try it out in advance. I'm probably going to get her the Claud Butler Urban 300 hybrid, available in frame sizes 16", 18" and 20". She's 5'3" with inside leg 30" and most size guides suggest that the 18" frame would be right, but an email from Claud Butler advises 16". I've measured her for the ape test, and she's on the negative side - ie short arms, so perhaps I should go for the 16". Does anyone have any advice? I understand that frame sizes are variable between bike manufacturers anyway, so how can one ever tell?




  • The RookieThe Rookie Posts: 27,748
    It depends on the seating position.
    30" legs at 5'3" should mean relatively long arms but short torso (arm length has a strong correlation to leg length).

    To me an 18" sounds too big, I'm 5'9" with 29" legs and ride 19" hybrid as my torso is long, your partner's torso is a lot shorter (torso accounts for more of the cockpit length than arms) so I'd be looking at the 16" frame.

    Can you find a geometry guide as it's effective top tube length that matters (add 20mm if it has an offset seatpost plus stem length).
  • Ed AddisEd Addis Posts: 6
    Thanks very much for your help. I had come to the same conclusion, and have now ordered the 16" frame size.

    Thanks again

  • RutlandGavRutlandGav Posts: 144
    After the fun and games I had with my bike, I'd check the crank arm lengths first up. They're not easy to put right if too long, and overlong cranks will cause knee problems after a few weeks, which you don't want.

    What problems can an oversize frame cause a person, apart from what i've just mentioned?

    In my experience it is always possible to lower the seat to accommodate a much shorter rider provided the cranks are ok, but you do get reduced standover height which isn't fun in traffic and can make mounting / dismounting a less than graceful process - particularly if you're as inflexible as i am. Then again most girls are pretty flexible aren't they? Thanks to a lifetime doing Aerobics/Yoga classes us blokes like to skip on.

    What about the arm length issue? If your arms are too short, what problem does that cause?
  • Zerotails99Zerotails99 Posts: 127
    Wrong size bike don't cause anybody any problems long term. That's because they are usually rusting away in the garden.
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