Do I have long femurs?

Discussion in 'Road Cycling' started by hansenator, Feb 9, 2014.

  1. hansenator

    hansenator New Member

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    Hello everyone. First time poster. I wasn't sure where bike fit questions should go, I hope this the right place. I bought a LeMond Poprad a few years ago and it seems like, no matter how I adjust it, it just doesn't feel quite right. I was later told those frames where made for people with long femurs and, while my legs are long, I think a lot of it is shin length. What is considered to be "long femurs"? I'm trying to determine if the frame isn't going to work for me or if it's just not fitted right. Thanks.
     
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  2. danfoz

    danfoz Well-Known Member

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    A long femur would probably indicate a longer than normal femur based on some population size. You'd have to check some sample of medical records and extrapolate a formula, or since this is the internet such information may be found easily enough. I think whoever told you that probably wanted to sound smart (even though it may have been well meaning), as "long femurs" was one of the sports catch phrases for a few years. While Greg may indeed have had a long femur, I find it hard to believe a whole line of bikes would have been designed around the companies owner and not the general population.

    Looking at something I grabbed of the web for the Poprad I see a 55cm frame with a 56cm top tube and a 73degree seat tube angle. Seems pretty standard for a road bike. Back in the day many bikes had a square geometry, i.e a 53cm had a 53cm top tube, however seems like top tubes have been getting longer across the spectrum of brands.

    Is there a particular aspect of the fit bothering you that can be pinpointed? For the most part varying frame geometries can be compensated for with saddle fore/aft, saddle height, and stem lengths, and handlebar heights once saddle position has been defined. It's a different story if the saddle needs to go further back or forward beyond the space the rails allow, but even that can be corrected somewhat by a seatpost with more or less setback.

    I'm thinking femur length would have more of an impact on crank arm length which may be something to look at if the bike fit feels "off" beyond the typical position corrections mentioned above.

    Some links I just found -
    http://www.hayshighindians.com/academics/classes/csadams/Labs/Vista%20graphing%20in%20excel/Excel%20graphing%20-%20height%20v%20femur.html
    (looks like there's a small data pool for some SWAG comparison)

    http://www.billbostoncycles.com/crank_length.htm
     
  3. hansenator

    hansenator New Member

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    Thanks for the reply. Fit-wise: The seat height is fine, I'm comfortable with the distance to the handlebars and the handlebar height. It just feels like my feet aren't pushing down at the right angle. I move the seat forward and back and can't get it to feel quite right. I have two other bikes which fit fine, it's just the Poprad I have this problem on. I like the bike but I'm starting to wonder if the frame just doesn't work for me.
     
  4. oldbobcat

    oldbobcat Well-Known Member

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    With a tape measure, a borrowed handlebar stem or two, and an allen wrench, you should be able tot duplicate the fit of one of these other bikes on your Poprad.
     
  5. ambal

    ambal Active Member

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    When you post an actual photo of your femur, i'll make a yes or no decision on the length. [​IMG]
     
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  6. oldbobcat

    oldbobcat Well-Known Member

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    Here's what long femurs looks like on a guy of modest height.
    [​IMG]
    Regarding fit proportions in general, bikes started getting longer in the top tube by the end of the 1980s. In the post '90s period, LeMond bikes are a bit different because he always measured center to center rather than center to top. Which begs the question, with fat, tapered, and oddly shaped tubes, center of what? And, with compact geometries (short seat tubes) and "endurance" geometries (tall head tubes), top of what?

    Even in the era of "standards," (pre-1990?), most manufacturers measured center to top. Most Italian builders measured center to center, which reduces the nominal size about 1.5 cm. And then, the "square" paradigm usually applied only to medium (54-56 cm) frames, with top tubes getting shorter on the larger sizes and longer on the smaller ones.

    What am I getting at? That nominal sizes are just that and you need a measuring tape to be sure of what you're getting.
     
  7. hansenator

    hansenator New Member

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    I had the bike up on the trainer today and was playing with the fit. I might need a different seat post or something. I have the seat as far forward as it will go and I keep feeling like I want to move it even farther forward. I don't know how accurate that bit with the plumb bob is but I did check it and, from my knee, it does come down well behind the pedal axle. I'm tempted to think maybe the frame is too long.
     
  8. danfoz

    danfoz Well-Known Member

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    If the seatpost is a setback type, a straight post might get you closer to where you believe you need to be.
     
  9. oldbobcat

    oldbobcat Well-Known Member

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    Could be. When selling LeMonds, I always ended sizing down from where they'd be on a Trek, etc.

    The touch points on your bike form a triangle--bottom bracket to butt of saddle to handlebar and back to the bottom bracket. Well, you don't touch the bottom bracket, but it is the center of rotation for your feet. Compare these measurements from a bike that fits to what the Poprad gives you. Then try to finesse those dimensions to the Poprad.

    The fallacy of shortening the reach from saddle to handlebar by sliding the saddle forward will show up in the span between the handlebar and the bottom bracket.
     
  10. hansenator

    hansenator New Member

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    I suppose the frame doesn't seem too long as much as I feel like I'm too far behind the bottom bracket. The length to the handlebars is actually ok. I'll try with a straight seatpost and see how that feels.
     
  11. hansenator

    hansenator New Member

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    I did try a straight seat post and I think it's kind of borderline. I still feel like I want to sit towards the front of the saddle. Maybe I need to give it a better chance than a few minutes on the stationary trainer can offer? I played with the height a bit but that didn't change my fore-aft perception. I tried dropping a plumb line from my knee and it still comes behind the pedal axle unless I scoot forward a little, for what that's worth.

    .[​IMG]
     
  12. danfoz

    danfoz Well-Known Member

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    The KOPS is only a starting guideline FWIW.

    It does work very well for me though, maybe 1/8" behind, but any further back and I get very sore on the upper hamstrings and loose my stratospheric spin rate, and any farther forward and I get a horrible pain above the knee. Who knows if it's my optimal. just been pedaling like this for decades and my body doesn't want to hear about any changes.

    You picked a sweet seatpost btw.
     
  13. Timmbits

    Timmbits New Member

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    That made me chuckle a bit, when I read the title.

    Women tend to have a longer leg length to total body length than males. However, there are exceptions. Most frames are designed accordingly, and there are exceptions to that too.

    Most bike frames for men are made "square" (top tube length = seat tube length), or with a top tube slightly longer than the seat tube.


    Fore-aft seat tube positioning must not be used to compensate a wrong-sized top tube.

    Proper seat tube position is when a plumb line through your kneecap intersects with the pedal axle, with the foot on the pedal and the crankarms are horizontal (measuring knee to axle with crank at the 3 0'clock position).

    If the top tube is too long or too short, you can try to compensate with a different stem length, or change bikes. To check for proper stem length, a plumb-line from your nose should arrive about 1 inch (25mm) behind the handlebar.

    But first, make sure that your seat height is correct. To determine this, place yourself near a wall or something you can use for support, while on your bike. Place your heels on the pedals, and pedal backwards. Have a friend look at your hips from behind while you do this. The correct seat height, is the highest, pedalling backwards in comfort, without your hips rocking. Your hips should remain horizontal to each other. Another way, is to place your crankarms vertical, and with a foot in the bottom position, there should be a slight bend in your knee. But the former method is more reliable.

    So, here are the steps in order, following instructions above:
    1. make sure you have proper seat height
    2. adjust seat fore-aft position
    3. get the right stem length to feel comfortable. if you need a stem that seems too short or too long, consider a different bike - a top tube length that is too long will be hard to fit, will have less nimble handling, and will give an improper fire-aft weight distribution. same with a top tube that is too short (but that is less common).

    It can take some searching to find a pre-manufactured (as opposed to custom made) bike that has the right proportions. If you need a new frame, check out the frame specs before buying. Compare with your model - better yet if you have another bike that feels right, as a starting point.

    The proper frame, with the proper fit, will always feel right. It will just feel natural, as it should, because the bike is to be an extension of the rider's body, and make one with it.
     
  14. oldbobcat

    oldbobcat Well-Known Member

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    I talked with a product manager for Trek's WSD program, who told me that the "girls have longer legs" assumption is just wrong, And in my experience fitting women to bikes, she's right. Lots of women have stumpy legs. But there is a tendency toward shorter arms, and there is something about the way they use their hips and shoulders that makes shorter top tubes and taller head tubes advantageous.
     
  15. Timmbits

    Timmbits New Member

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    It is the statistics, and bike dimensions are based on statistics. But it's nice that Trek is finally fitting bikes to women's very varied physiologies, because up until now, the bike frame geometry of the Treks in particular was among the most standard I have ever seen. It's about time they put some effort into this - I mean, it is 2014 after all. Sorry, I didn't mean to strike a sensitive chord with my statement: can we get back on topic please?

    I would be interested to know the OP's height, and inseam, and maybe the frame geometry of the bike in question. Then I could help. Without that, I'm signing off.
     
  16. hansenator

    hansenator New Member

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    I had my wife help measure my inseam and it looks about 35.25 inches. Height is 6 feet, 1.5 inches. Not sure about geometry but it is a LeMond Poprad. I had the stem switched to bring the handlebars up and a little closer and that helped. My feet are a size 14 and I've wondered how that affects it? Would long feet require moving the seat back a bit?
     
  17. oldbobcat

    oldbobcat Well-Known Member

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    Proportional to your height, your leg length is definitely longer than average, although it doesn't quite put you in outlier territory. Your feet are huge for your height. It's been a long time since I've measured a Poprad, but if memory serves me, it's not particularly long in the top tube, but the head tube is not extended as on most newer bikes. Are you on a 59 or 61?

    Unusual proportions are one reason I don't put much truck in KOPS (knee over pedal spindle). I recommend setting the saddle where you can feel your center of gravity over the feet when your hands and torso are in your most used pedaling position. For most people, this is hands over the the brake hoods. By this method, a lower torso angle and large feet would indicate more setback. The idea is to find a setback that lets you alternately push down and pull up on the hoods, and allows rise to a sitting up position without pushing off with your hands. Once you establish your preferred back angle and saddle setback, adjust the stem length to correct the reach, then fine tune.
     
  18. Timmbits

    Timmbits New Member

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    What's nice about the knee over pedal-spindle, is it's simplicity. Whether you have some extra proportion in the foot length, tibia, femur - it makes up a set of levers, from hip to the ball of the foot. With your knee over the spindle, you have the best position for transmission of force, with no energy wasted in a vector pointing away from the intended direction of the force.

    I'm like you, with longer legs for my height. For my fixie, I found a bike that had a shorter top tube and longer seat tube than the norm. I've been searching for a frame like that ever since I had one of similar proportions in my teen racing years, and I'm so happy I found one again! OK, back to your predicament.

    For our situation (because I'm in the same as you), we need to check the frame geometries. I'm guessing you use a 24" frame right now?
    With components being made of carbon fiber and weighing next to nothing these days, you're better off having a frame an inch shorter, to get a proper top tube length, and make up for it with an extra inch of seat post length. The bike I found for myself, was a track bike, that I setup as a fixie for the road. It's stiff as heck but handles like a charm - very responsive. But that comes with steeper angles, shorter wheelbase (shorter top tube and shorter chainstays), and a higher bottom bracket, which may not give the handling characteristics that you are looking for. I looked up your bike, and although I couldn't find the frame geometry table, I did learn that it was designed for cyclocross and sport riding. That's quite a bit more tame (and more comfortable) than a criterium frame. (and I'll go out on a limb here, but I wouldn't be surprised if it had a longer than average top tube length, exactly what you don't want).
     
  19. hansenator

    hansenator New Member

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    Thanks for the advice. I'll definately check out the center of gravity over the pedal adjustment. The reach actually feels ok, I had the stem swapped and my arms are longer than average so I think that helps.
     
  20. Timmbits

    Timmbits New Member

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    Indeed, your arm span, finger ends to finger ends, are your height.

    What kind of riding do you do with your bike? Touring, sport riding, racing, cyclocross?
     
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