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  1. #1
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    Question: Saddle position relative to crank length

    I'm starting to get the feeling I might need to slide my saddle a "teency" bit back after getting in a few rides on my longer, 182.5mm cranks. Granted, it's only a 2.5mm difference from before, but I'm definately noticing it.
    Thoughts?

  2. #2
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    Fit Kit Flashback....

    ACCCCCcccccccckkkkkkkkk.... Now you're bringing out the wayback machine. (Insert Wayne and Garth sound effect here).

    It has been almost 15 years since I had my fit kit training, and almost 13 years since I last used that triaining, so please correct me if I'm wrong.

    The way we used to calculate proper saddle position was to run a plumb line from just below your knee down past your foot. The goal was to get the center of the pivot of your knee over the pedal spindle while your foot is at the bottom of its stroke. *** With that in mind, as long as your saddle was adjusted down a little to accomodate for the longer cranks (my guess would be 2.5mm lower), you should be positioned similarly. At the front of your pedal stroke your foot will be 2.5mm further forward than it used to be and correspondingly 2.5mm back further at the back of your pedal stroke.

    *** Note the corrections in the posts below. I had you measuring at the wrong point in the pedal stroke.

    Hopefully that makes sense. A lot of beer has been processed since I last did a fit kit for a customer.

    Peter
    Last edited by Objectionable Material; 12-16-2004 at 11:35 AM.
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  3. #3
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    The way we used to calculate proper saddle position was to run a plumb line from just below your knee down past your foot. The goal was to get the center of the pivot of your knee over the pedal spindle while your foot is at the bottom of its stroke. With that in mind, as long as your saddle was adjusted down a little to accomodate for the longer cranks (my guess would be 2.5mm lower), you should be positioned similarly. At the front of your pedal stroke your foot will be 2.5mm further forward than it used to be and correspondingly 2.5mm back further at the back of your pedal stroke.
    Peter
    That is not quite right. The cranks should be parrallel to the ground and the plumb line should fall to the middle of the (forward, duh!) pedal spindle, or slightly behind it, for longer legs.
    That being said, if your position was correct with the shorter cranks, lowering the saddle to adjust for the longer crank will also move it forward, and very little adjustment should be nessesary, fore/aft.
    Todd............. If you can't be kind, at least have the decency to be vague

  4. #4
    DSR
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    One sidenote, not fore-aft but up-down. Just be sure that you run the saddle high enough that your knee if comfy at the top of the stroke. I switched from 175s to 180s and was focused more on my leg extension on the downstroke but my knee started bothering me because my knee was hitching in at the top of the stroke since I was out of room at the top. Bumped the saddle up some more and all was good again. Something to just watch for since saddle height is generally set by leg extension. S

  5. #5
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    Quote Originally Posted by DSR
    One sidenote, not fore-aft but up-down. Just be sure that you run the saddle high enough that your knee if comfy at the top of the stroke. I switched from 175s to 180s and was focused more on my leg extension on the downstroke but my knee started bothering me because my knee was hitching in at the top of the stroke since I was out of room at the top. Bumped the saddle up some more and all was good again. Something to just watch for since saddle height is generally set by leg extension. S
    I am confued, If you went to a 5mm longer crank, that would in effect raise your saddle 5mm, then you further raised the saddle????
    That should cause your knee to over extend, and/or, cause you hips to rock as you pedal through the bottom of your stoke. Not good. Unless your saddle was too low to begin with.
    Todd............. If you can't be kind, at least have the decency to be vague

  6. #6
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    Quote Originally Posted by 32seventeen
    That is not quite right. The cranks should be parrallel to the ground and the plumb line should fall to the middle of the (forward, duh!) pedal spindle, or slightly behind it, for longer legs.
    That being said, if your position was correct with the shorter cranks, lowering the saddle to adjust for the longer crank will also move it forward, and very little adjustment should be nessesary, fore/aft.
    Good catch. That was the one thing I was foggy on. I now remember sticking the silly little level on the cranks and trying to get someone to hold the cranks horizontal.

    Thanks for the clarification. I guess I should have moderated some of that beer intake after all.

    Peter
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  7. #7
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    Quote Originally Posted by 32seventeen
    I am confued, If you went to a 5mm longer crank, that would in effect raise your saddle 5mm, then you further raised the saddle????
    That should cause your knee to over extend, and/or, cause you hips to rock as you pedal through the bottom of your stoke. Not good. Unless your saddle was too low to begin with.
    If you lengthen your cranks, you LOWER your saddle. You definitely don't want to over extend.

    Peter
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  8. #8
    DSR
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    Quote Originally Posted by 32seventeen
    I am confued, If you went to a 5mm longer crank, that would in effect raise your saddle 5mm, then you further raised the saddle????
    That should cause your knee to over extend, and/or, cause you hips to rock as you pedal through the bottom of your stoke. Not good. Unless your saddle was too low to begin with.
    If you lengthen the cranks, yes you've extended the cranks and effectively raised your saddle on the downstroke but at the same time you've lowered the saddle/seatpost at the top of your stroke. If you then lower your saddle 5mm to compensate for just the downstroke change, then your knee is going to be 10mm closer to your saddle/butt/hip/whatever (5mm from the longer cranks and 5mm from you lowering your saddle) at the top of the stroke. My problem was the my knee was too cramped on the upstroke and was hitching inward since it was out of room and therefore the ensuing knee pain. Net-net, longer cranks = greater radius, larger circumference and (given no change in seatpost height from the old 175s) longer leg extension AND a greater knee bend at the top of the stroke. S

  9. #9
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    That makes sense. My knee problems have always come from overextension. Long cranks are not for everyone. I'm using 180s and want to go to 190s when I get done printing new money.

    Peter
    If a man talks dirty to a woman, it's sexual harassment. If a woman talks dirty to a man, it's $3.95 per minute.

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  10. #10
    DSR
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    Quote Originally Posted by Objectionable Material
    If you lengthen your cranks, you LOWER your saddle. You definitely don't want to over extend.

    Peter
    See my prior post. Yes, you may lower your post or keep it the same. It all depends. I'm just saying that if you lower your post to address the leg extension issue, then you just have to be sure that your knee isn't overly bent at the top of the stroke since your foot is now 5mm+ (depending on how much you've lowered the saddle) closer to your butt or saddle or whatever. This can put some real strain on the knees especially when cranking in singlespeed mode. S

  11. #11
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    Quote Originally Posted by DSR
    If you lengthen the cranks, yes you've extended the cranks and effectively raised your saddle on the downstroke but at the same time you've lowered the saddle/seatpost at the top of your stroke. If you then lower your saddle 5mm to compensate for just the downstroke change, then your knee is going to be 10mm closer to your saddle/butt/hip/whatever (5mm from the longer cranks and 5mm from you lowering your saddle) at the top of the stroke. My problem was the my knee was too cramped on the upstroke and was hitching inward since it was out of room and therefore the ensuing knee pain. Net-net, longer cranks = greater radius, larger circumference and (given no change in seatpost height from the old 175s) longer leg extension AND a greater knee bend at the top of the stroke. S
    I understand, that is true. At the same time you can do a lot of damage to your knees by having your saddle too high. It sounds like the longer cranks don't work very well for you. What is your inseam? Maybe you would be better going back to a 175? Be carefull I'm just tryin to help.
    Todd............. If you can't be kind, at least have the decency to be vague

  12. #12
    DSR
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    Quote Originally Posted by Objectionable Material
    That makes sense. My knee problems have always come from overextension. Long cranks are not for everyone. I'm using 180s and want to go to 190s when I get done printing new money.

    Peter
    Got it. Yeah, I had to hop on my imaginary bike to make sure I wasn't screwed up in the head on this one! Obviously the trick is to find that happy medium to avoid both over-extension and extreme knee bend (or whatever the opposite of over-extension is called). Anyway... whatever doesn't hurt is good! S

  13. #13
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    Quote Originally Posted by DSR
    Got it. Yeah, I had to hop on my imaginary bike to make sure I wasn't screwed up in the head on this one!
    I'm glad I'm not the only one that does this. People in my office look at me like I'm nuts.

    Somehow they seem to think that hopping on my imaginary bike *is* a sign that I'm screwed up in the head.

    Peter
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  14. #14
    DSR
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    Quote Originally Posted by 32seventeen
    I understand, that is true. At the same time you can do a lot of damage to your knees by having your saddle too high. It sounds like the longer cranks don't work very well for you. What is your inseam? Maybe you would be better going back to a 175? Be carefull I'm just tryin to help.
    My inseam is 34". I've got it all set up nice and comfy now. I always ran my post a tad low (mostly so I could drop behind the saddle easier in techy downhill sections) and switching to 180s just bumped me into the red zone at the top of my stroke. I bumped my post up and bit and have been good for some time now. Of course my hip is bothering me these days but that's because I went down hard and went hip bone to rock which is never good. Anyway... S

  15. #15
    DSR
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    We're all screwed up in the head! I brought up mtbr to my wife once and she got all freaked out that I post messages in some "bike cult chatroom." Her words. I was basically like "yeah, I guess that is about what it is", paused and then quickly changed subjects before it went down some unknown path. My goal though is to slowly get her sucked into the cult that we mountain biking! S

  16. #16
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    Quote Originally Posted by DSR
    My goal though is to slowly get her sucked into the cult that we mountain biking! S
    Careful!

    I've been trying to get my wife excited about mountain biking, and then one day she mentioned that she'd like to try road biking. Ended up getting her a road rig for her wedding present..
    Take the long cut, we'll get there eventually.

  17. #17
    DSR
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    Ha! Yeah, we're actually starting with the road bike and then I'm hoping to add mtb into the mix. More gear, but hey, I'm in no position to whine about that given my constantly revolving bike stable! My biggest mtb hurdle with her is self-created - all the times I've come home battered and bloody! Chicks dig scars... just not on themselves. Actually, I don't think they dig scars at all. Probably just a stupid guy thing.

    Sorry for completely hijacking this thread now! S

  18. #18
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    the myth of KOPS according to Keith

    Quote Originally Posted by 32seventeen
    That is not quite right. The cranks should be parrallel to the ground and the plumb line should fall to the middle of the (forward, duh!) pedal spindle, or slightly behind it, for longer legs.
    That being said, if your position was correct with the shorter cranks, lowering the saddle to adjust for the longer crank will also move it forward, and very little adjustment should be nessesary, fore/aft.
    Check out Keith Bontrager's rants about fit and KOPS myths.
    http://www.bontrager.com/keith/rants.asp?id=12

  19. #19
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    Padre,

    It seems people on this board are all over the place with regard to your question. Here's what I do:
    1. Sit on saddle with heels on pedals
    2. Backpedal
    If your hips rock, your saddle's too high. If they don't rock AT ALL, you might want to raise it a little to see if it's too low. Your hips should come dang close to rocking and some fudge factor either way is allowable. Fine tune with whatever feels best.

    If your knees feel constrained at the top of the stroke but your saddle is at the right height (based on my method of determining correct saddle height above), then your cranks are too long. Don't keep the too-long cranks and raise your saddle to alleviate constrained knees. Instead get shorter cranks.

    As for fore/aft saddle position, that is largely rider preference. KOPS (mentioned above) will get you close but I've found that backing away from KOPS a little in either direction is not necessarily bad. Personally, I prefer a slightly steeper seattube angle than many, which is not uncommon with long legs and long cranks. But you may perfer the opposite. That's okay.

    --Sparty



    Quote Originally Posted by Padre
    I'm starting to get the feeling I might need to slide my saddle a "teency" bit back after getting in a few rides on my longer, 182.5mm cranks. Granted, it's only a 2.5mm difference from before, but I'm definately noticing it.
    Thoughts?
    Last edited by Sparticus; 12-16-2004 at 03:10 PM. Reason: clarity
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  20. #20
    Recovering Weight Weenie
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    I read every post.....my head hurts....and I'm even more confused...

  21. #21
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    Hips rocking definitley best method

    Because it takes into account your actual pedaling style, toes down etc

  22. #22
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    fudge factor & saddle position... lol

    Quote Originally Posted by Sparticus
    Padre,

    It seems people on this board are all over the place with regard to your question. Here's what I do:
    1. Sit on saddle with heels on pedals
    2. Backpedal
    If your hips rock, your saddle's too high. If they don't rock AT ALL, you might want to raise it a little to see if it's too low. Your hips should come dang close to rocking and some fudge factor either way is allowable. Fine tune with whatever feels best.

    If your knees feel constrained at the top of the stroke but your saddle is at the right height (based on my method of determining correct saddle height above), then your cranks are too long. Don't keep the too-long cranks and raise your saddle to alleviate constrained knees. Instead get shorter cranks.

    As for fore/aft saddle position, that is largely rider preference. KOPS (mentioned above) will get you close but I've found that backing away from KOPS a little in either direction is not necessarily bad. Personally, I prefer a slightly steeper saddle angle than many, which is not uncommon with long legs and long cranks. But you may perfer the opposite. That's okay.

    --Sparty

  23. #23
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    I've always found the opposite to be true

    Quote Originally Posted by Padre
    I'm starting to get the feeling I might need to slide my saddle a "teency" bit back after getting in a few rides on my longer, 182.5mm cranks. Granted, it's only a 2.5mm difference from before, but I'm definately noticing it.
    Thoughts?
    When switching from, for example, 175 to 180mm cranks, I'd want to position the saddle 5mm further forward so my legs and feet remain in the same ideal position I had before during the downward power stroke. I'd also have to lower the saddle height by 5mm.
    Don't pay the $85 fee to ride land you own! Resist!

  24. #24
    ogarajef@luther.edu
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    It's a single speed, if I am sitting down that means I am getting a break and for that I am thankfull. I will be standing again before I even realize that my saddle height is too low or high. Get it close and let be, that my $ .02.
    "RIDE IT LIKE YOU HATE IT"

  25. #25
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    Quote Originally Posted by Sparticus
    Padre,
    It seems people on this board are all over the place with regard to your question. Here's what I do:
    --Sparty
    Have Dave, thanks for some insight I can actually understand AND apply.
    I'll test it out tomorrow.

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