18in GT frame for a 5ft 7 1/2 Munchkin?

contented
contented Posts: 83
edited January 2014 in MTB beginners
Hiya!
I've recently discovered that I'm a couple of inches shorter than I always believed and so my 19 inch Hardrock (and obviously my 20 inch Kraken) are too big for me.
I'm a novice so didn't really notice as I've never had anything to compare with and have yet to hit a proper track / route.
I'm on the lookout for a 17inch frame but just wondered -to those who know specific bike's geometry- whether the 18 inch 2009 GT Aggressor frame sitting in my garage will fit me?

I could build it up and see, but tbh I still wouldn't know and don't want to suffer the scorn of my lbs (at least until I've got a bit of cash to spend there).
Any advice appreciated, Happy New Year.

Comments

  • cooldad
    cooldad Posts: 32,599
    You have three random size bikes and haven't ridden any? Call me confused.
    I don't do smileys.

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  • cooldad
    cooldad Posts: 32,599
    It will probably still be too big, but you need to sit on one to make sure.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

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  • Chunkers1980
    Chunkers1980 Posts: 8,035
    All of that sounds very odd. It doesn't matter how short you believe yourself to be - you must sit on the bike and if it fits, it fits.
  • rockmonkeysc
    rockmonkeysc Posts: 14,774
    The seat tube length (18"/19" etc) is irrelevant. All three of those bikes could be very similar size or very different. The top tube length is more important.
    Transition Patrol - viewtopic.php?f=10017&t=13070235
  • contented
    contented Posts: 83
    Chunkers1980 wrote:
    All of that sounds very odd. It doesn't matter how short you believe yourself to be - you must sit on the bike and if it fits, it fits.

    Fair enough, I'll have to pop to the shop and have a look - that looks to be the only way. Both bikes fit, insofar as I can sit fairly comfortably and ride them, but I have only been on road / light trail so the issues with riding an oversized bike have not cropped up - that's why mine haven't felt too big, which a 20 inch surely must be.
    Sorry if it seems a bit vague, I'm only just getting the hang of cycling again and am still sitting and riding a bike in the same way as I did when I had a bmx as a kid.
    The reason for the 3 bikes in 3 sizes is I bought the 19in HardRock as a basic way into biking and thought it would fit my 5ft 9in (so I thought) frame, the Kraken was bought for the price of 2 new tyres (which it had on and I needed) and the GT frame was next to nothing with a Marzzochi Bomber still on it - both parts donors really.
    So, I'll use the lbs and keep my eye out for a smaller frame.
    Cheers for the advice :)
  • contented
    contented Posts: 83
    RockmonkeySC wrote:
    The seat tube length (18"/19" etc) is irrelevant. All three of those bikes could be very similar size or very different. The top tube length is more important.

    Ahh OK, there may be hope then. I'll look it up and learn a bit about top tube lengths. Thanks very much for the help Rockmonkey :)
  • arran77
    arran77 Posts: 9,260
    Chunkers1980 wrote:
    All of that sounds very odd. It doesn't matter how short you believe yourself to be - you must sit on the bike and if it fits, it fits.

    Nah, everyone guesses their height and then trusts the sizing chart, no need to test a bike for size :roll:

    :P
    "Arran, you are like the Tony Benn of smut. You have never diluted your depravity and always stand by your beliefs. You have my respect sir and your wife my pity" :lol:

    seanoconn
  • The Rookie
    The Rookie Posts: 27,812
    5'9.5" and I am just fine on a 16"

    As a rule of thumb, as you are about 3.5" below an average height, a medium sized frame would seem a bit large?
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • contented
    contented Posts: 83
    The Rookie wrote:
    5'9.5" and I am just fine on a 16"

    As a rule of thumb, as you are about 3.5" below an average height, a medium sized frame would seem a bit large?

    Cheers, I'll have to sit on a few to see. In spite of some of the more sarcastic replies, I did try out my spesh and Kraken before I bought them, but as I had no idea about proper riding position and I didn't fall off, they seemed fine and I bought them.
    It's only now I want to ride it 'properly' that I have seen the issue.
    It looks like you're right and I may need to go even smaller as I have wandered down to the lbs today and did some browsing and had a chat with the fellas.
    I know there's no strict rules, but if you feel just about right on a 16", that's got to be a good guide that anything above 17 is right out for me for a start.
    Thanks again for your help, HNY :)

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