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Unsure of frame size

dgendydgendy Posts: 26
edited September 2018 in Cyclocross
I bought a pinnacle arkose 4 recently. I got it in medium, assuming it was between 54-55 cm. I looked into quite a few bikes and was told by the customer service assistants I would need 54 cm and above for the frame given my height is 5"8. Although the bike is great it did seem a bit small. I have only just noticed the medium for this bike is actually 51 cm. It does specify the medium is for people between 5"7 and 5"10. Does anyone know the reason for this? Are there other features of a bike which mean it can still be classed as medium with a small sized frame?


  • imposter2.0imposter2.0 Posts: 11,003
    Depends how it is measured. If the seat tube measures 51, assuming the TT is slightly sloping, then that makes sense. A more useful measurement would be the top tube length, but either way it sounds like you have more or less the right size.
  • dgendydgendy Posts: 26
    Yes it is the seat tube length that is 51 cm. I thought all bikes companies would reference the same type of length?
  • I believe pretty much all companies do use the seat tube length as the bike size, but as already mentioned if they have a highly sloping top tube it will distort things (the bike will be longer than normal).
    Also, I have found that one company's medium is not necessarily the same as anothers.

    I am also 5'8", and ride a 54cm road bike which would correspond to a medium going by seat tube length (Domane Al, so it's shorter than most). However, when looking for bike sizes I find I am usually between the small or medium sizes. For example, to have the same reach as on my Domane, I would need a small pinnacle or a small Genesis Croix de Fer.

    However, if I wanted something that matched a real race bike geometry (such as a BMC Teammachine that I have my eye on) I would need the medium sizes for both of those bikes.

    To be fair, I do need a longer stem on the Domane to get me my reach- it was a warranty replacement frame for a much older 1.1 of the same size which had a longer top tube.

    For Cyclocross I actually ride a 51cm CaadX, it has only slightly less reach than my Domane but more stand over height which I appreciate, and I prefer the slightly shorter bike to let me move around a bit more and give me a more relaxed position to keep my weight further back.
  • I am actually 5"10 with shoes so border between medium and large. The medium just doesn't seem good for my back, do larger frames for road bikes reduce this issue?
  • imposter2.0imposter2.0 Posts: 11,003
    dgendy wrote:
    Yes it is the seat tube length that is 51 cm. I thought all bikes companies would reference the same type of length?

    no chance..
  • Fair enough! I guess it won't be that much difference between medium and large if I did fit in between those sizes.
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