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  1. #1
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    stack / reach changing with size of frame?

    A friend of mine - a tall guy - wants to buy a racebike. When we were discussing fit, we noticed something: bigger frames almost invariably have a higher stack / reach ratio.

    For example, my "53cm" Bianchi Intenso has a S/R ratio 1,47. But for a "61 cm" Intenso S/R = 1.56, and the "63 cm" has a S/R ratio 1.58.

    My frame is somewhere between stretched out and relaxed, but a frame that would fit him, would be (very) relaxed.

    Why does S/R grow so much with the size of the frame? Regulations? Geometrical limitations?

  2. #2
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    Quote Originally Posted by HFroller View Post
    A friend of mine - a tall guy - wants to buy a racebike. When we were discussing fit, we noticed something: bigger frames almost invariably have a higher stack / reach ratio.

    For example, my "53cm" Bianchi Intenso has a S/R ratio 1,47. But for a "61 cm" Intenso S/R = 1.56, and the "63 cm" has a S/R ratio 1.58.

    My frame is somewhere between stretched out and relaxed, but a frame that would fit him, would be (very) relaxed.

    Why does S/R grow so much with the size of the frame? Regulations? Geometrical limitations?
    Frame size to frame size, frames grow more in stack than they do in reach which is another way to put it. This is because human's 'typically' derive their height by longer leg length. There are exceptions of course.

    I have a friend is 5'9" and I am 6'1". When sitting for dinner or seated on an airplane, our eye height is the same from the ground. He is shorter because he has short legs and I am taller because I have longish legs.

    Frame sizes are of course derived by statistical norms of how people are built.

    But...and importantly, the proportion of a rider matters a lot on frame selection. So proportion of a rider should be taken into account when choosing a frame.

  3. #3
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    Quote Originally Posted by 11spd View Post
    Frame sizes are of course derived by statistical norms of how people are built.
    OK, sounds plausible.

    Quote Originally Posted by 11spd View Post
    But...and importantly, the proportion of a rider matters a lot on frame selection. So proportion of a rider should be taken into account when choosing a frame.
    Of course, but the thing is: frames are presented as "relaxed" or more "stretched". Giant Defy = relaxed; Giand TCR = for people searching for a more streamlined position. Etc.

    I feel now that this is a bit misleading. My Intenso was sold to me as an "in between" frame, and the fact that my 53 cm indeed is in between is what I like about it. But bigger sizes aren't in between at all.

  4. #4
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    Quote Originally Posted by HFroller View Post
    OK, sounds plausible.



    Of course, but the thing is: frames are presented as "relaxed" or more "stretched". Giant Defy = relaxed; Giand TCR = for people searching for a more streamlined position. Etc.

    I feel now that this is a bit misleading. My Intenso was sold to me as an "in between" frame, and the fact that my 53 cm indeed is in between is what I like about it. But bigger sizes aren't in between at all.
    You asked really an overarching philosophical question based upon historical trends and my response is based upon how 'many if not most' derive their height. Taller people generally get most of their height in their legs. Head tube is an analog for leg length and top tube an analog for torso length. Of course arm leg is a factor as well and statistics generally confirm that those with longer legs also have longer arms but...there are notable exceptions.

    Even the convention of frame sizing is under siege so conventional norms have to be looked at with a degree of skepticism. Historically road bike frames have been more squarely proportioned relative to real or virtual seat tube length but many exceptions to this as well.

    Fit is a quandary wrapped in a conundrum and even a choice....to be racy or more geared to longer distance riding...or in between. I like others can ride multiple fits and each will serve me better in a given situation better than another.

    The enlightened consumer looks at every frame dimension when choosing a frameset which leaves most to get it wrong or at least less right because this takes years of study and trial and effort to determine what works best and moving target because our fitness changes as we age as well. Less 80 year olds on a TdF setup but I know nationally ranked late 60 y.o's that race 5 inches of drop.

  5. #5
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    Quote Originally Posted by HFroller View Post
    OK, sounds plausible.



    Of course, but the thing is: frames are presented as "relaxed" or more "stretched". Giant Defy = relaxed; Giand TCR = for people searching for a more streamlined position. Etc.

    I feel now that this is a bit misleading. My Intenso was sold to me as an "in between" frame, and the fact that my 53 cm indeed is in between is what I like about it. But bigger sizes aren't in between at all.
    Based on what are you saying bigger sizes are less aggressive? I'm guessing you are thinking more stack means less aggressive and not recognizing that taller riders will have a higher seat so that's not true as a rule.

  6. #6
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    Quote Originally Posted by Jay Strongbow View Post
    Based on what are you saying bigger sizes are less aggressive? I'm guessing you are thinking more stack means less aggressive and not recognizing that taller riders will have a higher seat so that's not true as a rule.
    Jay,
    He was looking at it, and rightly so as stack to reach ratio and was commenting that reach grows less and stack grows more as frame sizes get larger which is true. I explained this is statistically based that 'most' not all, tall people get their height in their legs. If a long reach and short stack is looked upon as an aggressive geometry which is true as well, then the OP has a good point if looking at geometry in this context. But taller head tubes and not much longer top tubes of bigger frame sizes is generally based upon how tall people are built.

    Btw, there are notable exceptions. Some know that Michael Phelps in many ways is a genetic freak. He is 6'4" and all torso and shortish legs. He gets his height from his torso. Btw, this also lowers his drag coefficient in the water and as a general rule, swimmers built like Michael are faster. Reason is his torso acts as hull of speed boat. Greater surface area lowers his drag coef in the water.

    I have a friend who is the same height as me who is physically very strong as well, can lift big weight. We are built completely the opposite. I have more a swimmers build as I grew up swimming and he is built like a weight lifter but isn't heavy. Our bikes are the complete opposite. His bike is low and long and mine is high and shorter. Our bikes reflect our body type. We stand eye to eye after a ride however.

  7. #7
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    I am a big fan of Giro Helmets and I wore them for over 20 years. I decided to try something new last year and I went shopping. I tried the Specialised helmets and I didn't like the fit. I loved the fit of POC but I don't love the price. I tried the Smith Route and I bought it.

    After a year of riding with the route, I can tell you that the Giro's Ventilation is awesome! The Route can be warm in the hot days. The Route is also heavier and I can feel the weight sometimes. But I love the helmet fits!! I am going to keep it. At the mean time, I am also shopping for a new one. Thinking about one from MET. I had a MET helmet 10 years ago and I love the fit. I may get another one because they are on sale at my local shop.

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