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  1. #1
    johnliu@earthlink.net jyl's Avatar
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    Son's Riding Position

    I'm glad we have this forum.

    Here are some pictures of my son on his current, small bike. I am building him a new, larger bike. I'm looking for any thoughts or criticisms of his position on the current bike, that I can use when picking frame size, components, and building up the new bike.

    Noodling along on the tops (there are interrupter brake levers there)



    Pretending to go fast (but actually coasting) in the drops



    Actually pedaling in the drops (and getting tired of riding back and forth while dad takes photos)



    The current bike, pictured, is a junior sized early '70s Peugeot with 26"/559mm rims. It used to be my old bike, when I was a kid, but not much besides the frame is now original. The frame is 19" (49 cm) center-to-center. As shown, the pedal-to-saddle (distance from pedal upper surface to midpoint of saddle upper surface) is 33.5", and, I think, he needs around 1" more (but the post is maxed out).

    Obviously, his new bike will be larger. It will be a small adult bike with 700C wheels.

    I've tentatively picked a new frame (call it frame A) that is 20.5" (52 cm) center-to-center. That will give him 34.5" pedal-to-saddle with a bit over a fistful of exposed seatpost (about 6"). He should be able to stand over it pretty comfortably, though we haven't tried yet. However, with frame A, he won't have near the saddle-to-bar drop that he currently has. The top tube will be significantly longer than his current bike.

    The alternative (call it frame B) is 19" (49 cm) center-to-center. So, not larger than his current frame, but this one is an adult frame for 700C wheels. That frame would allow a larger saddle-to-bar drop, and the top tube will be shorter, than frame A.

    Any thoughts? Is his current riding position one that you would try to replicate in the new bike, or should I be trying for something else? Would you go with frame A or frame B?

    The usage is weekend fun rides. We'll ride Seattle to Portland in July. He doesn't ride this bike to school/on errands, he has a hybrid for that.
    Last edited by jyl; 06-16-13 at 01:15 PM.
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  2. #2
    Travelling hopefully chasm54's Avatar
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    That frame is far too small, get the bigger one. The extreme saddle-bar drop is a consequence of it being too small. The bigger bike will allow him to stretch out more, so although the drop will be smaller he will be in a posture that is just as aero but less cramped.
    There have been many days when I haven't felt like riding, but there has never been a day when I was sorry I rode.

  3. #3
    Senior Member elcruxio's Avatar
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    Current position is too short.
    Drops position is ok but tops position way too short.
    I'd go with the larger frame since it's longer. You can start with a shorter stem and go longer as he grows. If you start with a 90mm stem you can add to the position reach up to 50mm. So the end result would be a 140mm stem. And if he outgrows that you can again get a new frame.

    Maxing out seatposts is rare these days since posts come in 350mm to 400mm. Of course more than two fistfulls of post showing will possibly make the riding position a bit low so don't cut the steerer tube in the next bike to a minimum. Leave a bit room for spacers under the stem.

    So a long post, long steerer and lots of stems should make the frame last a bit longer. Growing children are a headache in clothes and bikes.

  4. #4
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    Standard procedure for EVERY new bike is a new fitting, whether by shop or DIY (if you are skilled at it). He needs the new bike, for sure.

    Just make sure the saddle height & fore/aft is correct before positioning the bar/stem. It gives him the proper base from the start, and only a degree or two of tilt MAY be required after bar position.

    I'm assuming you know the measurements to take for basic fitting...?

  5. #5
    Senior Member elcruxio's Avatar
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    Quote Originally Posted by DX-MAN View Post

    I'm assuming you know the measurements to take for basic fitting...?
    Oh yes do tell!
    I've been dying to get my hands on the fitting formulas which you use with body measurements.

  6. #6
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    Wow, you've never come across any?

    The 'old' racer method (I believe it started with the legendary Eddie B.) was to measure the rider crotch-to-floor, multiply by .883, and set bottom-pedal-to-saddletop height there. Greg LeMond advocated using .885. I say either is a good starting point, to be further modified to the rider's comfort. (Too high, you get crotch-rub on the saddle, too low, you get a future filled with knee problems) I personally use the 'ancient' heel-on-pedal method -- comfortably centered on the saddle, heel on bottom pedal, leg locked out straight, which gives a good bend in the knee when the BALL of the foot is on the pedal.

    Fore/aft saddle position is done by the 'plumb bob' method -- dangling a weighted string off the front of the knee with the pedals at 3 o'clock/9 o'clock, the string should either bisect the pedal axle or be just behind it, to make best use of the leg muscles. Forward position (in most cases) will usually negate the strongest leg muscles needed for good pedaling. Too far back will overwork the legs.

    Another measurement is saddle-to-stem, roughly the same as fingertip to outside of bent elbow. Again, this is a STARTING point, everyone is best fit with small adjustments to these base measurements.

    I also default to a span of no more than 1" above to 1" below saddle height for the bar, and customize from there; more than a few roadies will argue that, and that's fine, they've already BEEN fitted to theirs.

    What EVERYONE should do is, once you have found that proper fit, TAKE MEASUREMENTS and duplicate them as closely as possible for future bikes.

  7. #7
    Senior Member elcruxio's Avatar
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    Quote Originally Posted by DX-MAN View Post
    Wow, you've never come across any?

    The 'old' racer method (I believe it started with the legendary Eddie B.) was to measure the rider crotch-to-floor, multiply by .883, and set bottom-pedal-to-saddletop height there. Greg LeMond advocated using .885. I say either is a good starting point, to be further modified to the rider's comfort. (Too high, you get crotch-rub on the saddle, too low, you get a future filled with knee problems) I personally use the 'ancient' heel-on-pedal method -- comfortably centered on the saddle, heel on bottom pedal, leg locked out straight, which gives a good bend in the knee when the BALL of the foot is on the pedal.

    Fore/aft saddle position is done by the 'plumb bob' method -- dangling a weighted string off the front of the knee with the pedals at 3 o'clock/9 o'clock, the string should either bisect the pedal axle or be just behind it, to make best use of the leg muscles. Forward position (in most cases) will usually negate the strongest leg muscles needed for good pedaling. Too far back will overwork the legs.

    Another measurement is saddle-to-stem, roughly the same as fingertip to outside of bent elbow. Again, this is a STARTING point, everyone is best fit with small adjustments to these base measurements.

    I also default to a span of no more than 1" above to 1" below saddle height for the bar, and customize from there; more than a few roadies will argue that, and that's fine, they've already BEEN fitted to theirs.

    What EVERYONE should do is, once you have found that proper fit, TAKE MEASUREMENTS and duplicate them as closely as possible for future bikes.
    Ah... well, I knew all of those...
    I'm actually looking for the formulae which you use to get bike measurements from body measurements.
    Like saddle tip to brake hood with forearm, arm and trunk measurements or setback with inseam, femur and tibia.
    Those would be seriously useful, although one cab always use the online fit calculators.

  8. #8
    johnliu@earthlink.net jyl's Avatar
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    Okay, stripped down frame A and took it to the bike shop to be spread to fit a 130mm rear hub.

    Is the saddle to bar drop shown too large? It looks pretty aero in the drops, and he can ride up on the tops if needed.
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  9. #9
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    Quote Originally Posted by elcruxio View Post
    Ah... well, I knew all of those...
    I'm actually looking for the formulae which you use to get bike measurements from body measurements.
    Like saddle tip to brake hood with forearm, arm and trunk measurements or setback with inseam, femur and tibia.
    Those would be seriously useful, although one cab always use the online fit calculators.
    You're asking the wrong one, pal. I live in the real world.

  10. #10
    Travelling hopefully chasm54's Avatar
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    Quote Originally Posted by jyl View Post
    Okay, stripped down frame A and took it to the bike shop to be spread to fit a 130mm rear hub.

    Is the saddle to bar drop shown too large? It looks pretty aero in the drops, and he can ride up on the tops if needed.
    If he can handle it comfortably, fine. You may find, though, that when he is stretched out a bit more it would be natural for the bars to come up a bit. He'd still be riding with a flat back.
    There have been many days when I haven't felt like riding, but there has never been a day when I was sorry I rode.

  11. #11
    Senior Member zandoval's Avatar
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    Very nice bike to begin with but on the small size - I don't ever remember getting my GROWING boys shoes that fit perfectly... This healthy kid could be two feet taller the day after tomorrow....

  12. #12
    Senior Member elcruxio's Avatar
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    Stems stems stemmmmmmsssss!

  13. #13
    johnliu@earthlink.net jyl's Avatar
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    When I was a kid, everything I had was the wrong size. Bikes way too big, shoes too large, pants too big. I was supposed to grow into them.

    When I got that little Peugeot, I was only 9 y/o and I couldn't even stand over it. Had to learn to ride on a bike that I couldn't straddle. By the time I finally grew into stuff, it was all beat up.

    I promised myself that, if I could afford it, my kids would get stuff that fit. I can afford it, and better yet I like - and my kids also like - used stuff, which is called "vintage" now and cool, doncha know, so I can even better afford it, without feeding the disposable consumer crap machine. I don't mind building my son a vintage bike that will only fit him for a couple of years. He'll be taller than me so this won't be his last bike.

    Wonder what the next will be? We could keep doing the vintage steel with modern bits theme. I've got a '61 Specislissima sitting in the basement, wonder how that would look with Di2? Just a thought, just a thought.
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  14. #14
    johnliu@earthlink.net jyl's Avatar
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    I'm back. Here is the bike referred to as "frame A", not completely "finished" but mostly done.

    What do you think about this fit?



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  15. #15
    Travelling hopefully chasm54's Avatar
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    Looks good to me. And a beautiful bike, btw.
    There have been many days when I haven't felt like riding, but there has never been a day when I was sorry I rode.

  16. #16
    Senior Member brianmcg123's Avatar
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    1000 times better. He looks so much more comfortable.
    Everyone's a roadie, they just might not know it yet.

  17. #17
    johnliu@earthlink.net jyl's Avatar
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    I wonder if his saddle is still a little low? He is very flexible, and can handle a deeper saddle to bar drop than shown.

    I'm going to try shifting his saddle forward a bit, and a corresponding adjustment higher.
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