Bike sizing for Rocky Mountain (do they tend to be sized short?)- Mtbr.com
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  1. #1
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    Bike sizing for Rocky Mountain (do they tend to be sized short?)

    I found a used 04 RM Hammer for a good deal online. I am 5'10/11 and 170-175 with an inseam of 32/33. The bike is a size 17.5. The thing I am worried about is the size. I looked online at Rocky Mountain bikes and they have the stand over height of 743mm which is like 29.25 in, so it should give me a good 2-3 inches clearance which is perfect. I am sorta between the 17.5 and 18.5. So the 18.5 is just like 3/4in higher than the 17.5. It also has a top tube length of 565mm. I heard someone tell me that RM tend to be sized shorter than other companies. So a 17.5 in a RM would be more like a 16 in another company. Is there any truth to that? Or can I get away with the 17.5?

  2. #2
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    So do they run a size smaller than other bikes?

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    focus on the TT

    Quote Originally Posted by tranzformer
    So do they run a size smaller than other bikes?
    565 millimeter = 22.244 094 488 inch [international, U.S.]

    I don't know how you ride or your needs but...

    I'm 5'10.5" and a 31" inseam, and I need a 24" TT. That said I ride FR with short 70mm stems; my trail bike is a large Enduro with 24" TT and an 80 or 90mm stem, I forget.

    So focus on the TT length 1st, never mind whats underneath, get the cockpit right.


    I'd (for myself) get the 18.5" frame for a trail XC ride because...

    580 millimeter = 22.834 645 669 inch [international, U.S.]

    Just my .02, Jim

    Rocky here

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    Quote Originally Posted by JimC.
    565 millimeter = 22.244 094 488 inch [international, U.S.]

    I don't know how you ride or your needs but...

    I'm 5'10.5" and a 31" inseam, and I need a 24" TT. That said I ride FR with short 70mm stems; my trail bike is a large Enduro with 24" TT and an 80 or 90mm stem, I forget.

    So focus on the TT length 1st, never mind whats underneath, get the cockpit right.


    I'd (for myself) get the 18.5" frame for a trail XC ride because...

    580 millimeter = 22.834 645 669 inch [international, U.S.]

    Just my .02, Jim

    Rocky here
    The only reason I am confused is that there is basically only a .5 in difference in the top tube length between the 17.5 and 18.5. So how does the top tube legnth typically get measured for someone? My arm length is about 26 in and I followed the directions here http://strongframes.com/how_to_order...3b8f69e2f86c6d

  5. #5
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    not sure...

    I fit mine by trial and error; errors cost a lot!

    read up here on TT and definition thereof: (scroll down a bit)

    http://sheldonbrown.com/frame-sizing.html


    Jim

  6. #6

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    Quote Originally Posted by tranzformer
    I found a used 04 RM Hammer for a good deal online. I am 5'10/11 and 170-175 with an inseam of 32/33. The bike is a size 17.5. The thing I am worried about is the size. I looked online at Rocky Mountain bikes and they have the stand over height of 743mm which is like 29.25 in, so it should give me a good 2-3 inches clearance which is perfect. I am sorta between the 17.5 and 18.5. So the 18.5 is just like 3/4in higher than the 17.5. It also has a top tube length of 565mm. I heard someone tell me that RM tend to be sized shorter than other companies. So a 17.5 in a RM would be more like a 16 in another company. Is there any truth to that? Or can I get away with the 17.5?
    By the sounds of your height and the fact that you usually fall between an 18.5 and a 17.5, I'd say the 17.5 will be an ok fit but you might need a longer stem to compensate. I personally always like to ride a bike before purchase. I'd recommend finding a Rocky dealer and try a bike with atleast similar geometry ie. a Blizzard, Vertex Team/70, or to a lesser extent a Vertex 10, 30, 50 which has a 5mm shorter top tube length. The Vertex will feel different due to the aluminim frames but will be good for figuring the fit of the shorter Rocky toptubes. You can take a look at the geometry for all Rocky bikes on the website which you can then compare to your current/past bikes.

    For referance, I'm 6' with a 32-33 inseam and I ride a 19.5 Blizzard with a 110mm stem which I find to be at my absolute reach within comfort/reason and I'm picking up a 90mm stem to tighten things up for myself. I honestly think an 18.5" would be a perfect fit for me (which I'm considering )

    For the record, this is my personal advice to you good sir. I work at Rocky but I'm just a grunt in the paint dept (just to clarify )

    Anyhow, best of luck with the bike!

    Cheers

    PS - Nothing rides like a steel RM IMHO

  7. #7
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    In comparison to my other bikes, yes.

    Quote Originally Posted by tranzformer
    So do they run a size smaller than other bikes?
    I am 5'11" and ride an 18.5" RM Vertex Team SC w/ a 110mm stem and it feels cramped compared to my other 18" frame(Kona with similar stem/bars, etc.). In other words, it has a shorter TT, I am going to try a 120mm stem to stretch things out a bit more. Most Rocky bikes I have ridden seem to feel shorter to me (i.e Hammer, Vertex, Element) than comparably sized bikes from other mfgrs. Everyone has different body builds that fit frames differently, try before you buy if possible. I have a 33" inseam and average torso length and reach(no monkey arms). My Kona frame seems to fit much better, although similar specs on paper and in the components build. I think a 17.5" frame would most likely be to small for you IMO, I would like to try a 19"to compare with mine. Hope this helps you some, good luck.

  8. #8

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    Quote Originally Posted by tranzformer
    So do they run a size smaller than other bikes?
    Rocky mountains do fit smaller than some other manufacturers but not all. I ride a 18" ETSX, which is the exact same frame size as a 18.5" Hammer, and it fits the same as my 17" Jamis Dragon. I am 5'-10.5" with a 32" inseam and the 18" RM frame (18.5" hammer) with a 100-110 mm stem length fits like a glove for aggressive use where I have the ability to be upright if I want to. I believe that the 17.5" Hammer would be too small for you no matter how you look at it.

    The thing most people miss about RM bikes is that they have a steep seat tube angle and require a seatpost with a 1" (25 mm) offset to position the saddle correctly. With a similar type of say Kona bike, you would only require a seatpost with a 1/2" (12 mm) offset to position the saddle in the same position to the BB. You always need to make sure that the saddle is located in the right place before deciding if the top tube is the correct length for you.

    A good rule of thumb for determining correct top tube length is to compare the top tube length to the cubit length of your arm. With the saddle in the correct position, place the tip of your elbow on the tip of the nose of the saddle and your arm extending towards the headset. If the frame has the correct top length for you, the tip of your middle finger should fall on the top cap bolt of the headset. This rule seems to automatically take into account the proportions of people's upper bodies.

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