Frame size calculation in the middle of stock frame sizes

Discussion in 'Bike buying advice' started by Bozidar, Feb 26, 2014.

  1. Bozidar

    Bozidar New Member

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    Hi all

    I am looking at different options to buy a road bike, but I can't seem to find a good match for a frame size.

    I used a lot of calculators to estimate a good frame size and all of them gave me results for a frame size (top tube, seat tube) that falls between the 54 and 56 stock sizes of frames, although the numbers are quite closer to the 56 frame.

    I tried a 56 frame bike, and wasn't too impressed with how it felt on my back and shoulders, I felt too extended when I had my hands on the brake hoods. When I put my hands on the straight part of the steerer, the position was great, but I hate not having my hands near the brakes.

    I come from a hybrid bike with rapid fire shifters so I am used to a very upright riding position with the brakes and shifters at my fingertips,
    I don't want to dismiss the frame size as wrong outright, but I need insight on what is the possible issue here:

    1. Is the frame I chose too large for me?
    2. Did I use the bike wrong (positioning my hands on the hoods of the brakes)
    3. Is my body just not used to the more extended position of riding a road bike.

    Sadly, the bike shops in my vicinity don't stock on all frame sizes to try out, so it's a lot of guesswork so far.

    Has anyone had a similar problem. I would appreciate any insight into frame selection and adjusting to a different riding position from people who did the same transition (hybrid to road bike)

    regards
    Bozidar Spirovski
     
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  2. Bozidar

    Bozidar New Member

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    Just to add some info. My measurements are
    Inseam 81cm
    Trunk 65cm
    Forearm 36cm
    Arm 68cm
    Thigh 61cm
    Lower leg 56cm
    Sternal notch 147cm
    Total height 180cm

    The calculator returned the following estimate for ideal frame
    Top Tube Length 56 - 56.4 Cm
    Seat Tube Range CC 53.6 - 54.2 Cm
    Seat Tube Range CT 55.3 - 55.8 Cm
    Stem Length 10.4 - 11 Cm
    BB Saddle Position 71.8 - 73.8 Cm
    Saddle Handlebar 55.3 - 55.9 Cm
    Saddle Setback 5.3 - 5.7 Cm
    Seatpost Type Not Setback
     
  3. alfeng

    alfeng Well-Known Member

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    FWIW. The "ideal" frame size is for the "ideal" rider whose flexibility matches that of a reasonably fit individual ...

    With THAT in mind, a Road bike frame with a 56cm top tube is typically appropriate for someone who is your height nine-times-out-of-ten UNLESS you have a severe handicap which needs to be accommodated ...

    BECAUSE you are accustomed to an upright riding position, your most obvious option while you become accustomed to the slightly more aerodynamic position include:

    1. shorter stem
    2. higher stem
    3. narrower handlebars
    4. CX auxiliary brake levers
     
  4. danfoz

    danfoz Well-Known Member

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    While I agree somewhat with Alf, and as he indicates some adjustments can be made much in the same way a tailor will adjust a suit off the rack (sleeve length, waist size, collar height, etc.), I would say one could go either way depending, and that figure may be closer to 7.5 out of 10 (kindly stated so you don't feel like too much like John Merrick).

    Some thoughts:

    1. At 5'9", with a 31.5" inseam, only slightly shorter than 180cm (but with a similar inseam) I need something with a 54.5cm top tube and a 90mm stem, OR a 53.5cm top tube and a 100mm stem. I don't have T-Rex proportion arms (I.e. stubs) but I do not have long arms either.

    - The stem lengths of the models in 56cm range probably vary between 100-110cm. There may be some leeway on shortening. Manufactures feature 90mm stems on most every stem model in their respective lineups for some purpose

    - My saddle tip to handlebar is 52.5cm, shorter than the established norm. Some people like to tell me I need a longer stem. Those people are not the ones riding my bike 50-100 miles. It should also be noted that different bar types i.e. "classic" bend vs. compact bars, place the shifters in a slightly different position, and can affect reach and/or drop by up to a centimeter or more depending on the handlebar specs.

    - riders should be comfortable in all hand positions on the bars, especially the hoods.

    - I would simply be unable to ride a bike position spec'd by many of the "calculators" because of the discomfort they would provide. I have been riding for three decades of which I have raced 7 seasons, on bike setups which I established using "guidelines", but ultimately not being afraid to change what didn't feel right.

    - after a long layoff returning to racing, I did need a higher and shorter position, and I did get slightly lower and more stretched out as I got more conditioned, but it wasn't anything more than 1cm longer, and 1 or 2cm lower. And it did require some stretching accompanied with growing pains.

    2. Most bikes I am in the market for (race bikes) with the shorter top tube length also have a correspondingly shorter head tube (putting me too low on the bars). When I go for the rise I prefer (without flipping the stem, or running too many spacers under the stem) the models usually have me too stretched out.

    FYI, Bianchi and Raleigh both come in models featuring 55cm top tubes, as do some other manufactures... longer than a traditional 54, but shorter than a 56. Some builders stagger 52, 54, 56, while others stagger 51, 53, 55, etc. You may find the temperature of the 55cm porridge just right...

    Road test a few bikes, drive further than the LBS if that's what's needed. And know that some things like stem length can be changed, usually at little or no fee. It's a big purchase, get it as close to ideal out the door as possible.
     
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  5. danfoz

    danfoz Well-Known Member

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    The main things regarding proper fit, and in this order of priority:

    1. Does my position allow me to control the bike effectively
    2. Does my position allow me to ride comfortably
    3. Does my position allow for a position to generate power, and finally if competing
    4. Does my position allow for adequate aerodynamics.
     
  6. oldbobcat

    oldbobcat Well-Known Member

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    There's nothing in your size or proportions that indicates a 56 wouldn't be right. Some of your issues might be from coming straight from a flat-bar hybrid, and some of them might be because you need to tune your fit.

    I tell newbies who want to get it right to embrace the forward-leaning torso position, don't fight it. You aren't going to drive your head into the pavement just because its in front of your knees.

    Bend from the hips, not the shoulders or lower back, and extend the back, don't slouch. And support the torso with the back muscles, not the arms. And if it feels like your body wants to topple forward unless the arms hold it up, slide the saddle back to shift the center of gravity over your feet. And lower it to accommodate the extra leg reach.

    And don't forget to sit up once in a while.
     
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