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How to determine correct saddle height for a bicyle?

  1. Jul 20, 2007 #1
    A numerical answer would be good.
     
  2. jcsd
  3. Jul 20, 2007 #2

    daniel_i_l

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    I think that you want you'r leg to be straight when the peddle is at it's lowest point.
     
  4. Jul 20, 2007 #3
    That is too extreme I think. I use to think that the optimal position is like the y=1/x graph. Where x=0 denotes leg perfectly straight. The closer x is 0, the better but never x=0 in order for y to be defined. So never the leg perfectly straight but a little bent. The less bent the better but always bent. Is that correct?
     
  5. Jul 20, 2007 #4

    cristo

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    You know, you could use google sometimes. I got loads of hits on saddle height.
     
  6. Jul 20, 2007 #5
    For a road bike, your leg should be slightly bent when at the bottom of the stroke.

    For most bikes in general, you should always be able to touch the ground with both your feet and balance when in the saddle. If you have to get off the saddle to reach the ground or to balance your bike, the saddle is too high.
     
  7. Jul 20, 2007 #6

    mgb_phys

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    Depends on the bike and terrain.
    For a road bike you want your leg to be slightly bent with the ball of your foot on the pedal and the pedal at the bottom of the arc. This gives the best use of your muscles.

    With an off road bike the frame size if more important as you want the maximum distance between the top bar of the bike and you. The distance depends on how aggresively you ride and how much you value anything you keep between your legs.

    There are lots of bike manufacturers sites that give relations between the frame size, your height and inside leg.
     
  8. Jul 20, 2007 #7

    chroot

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    You purchased your bike from a store -- go back to that store, and have them do a basic fit. They should do it for free, and it should take only 15 minutes or so. Your leg should indeed be slightly bent at the bottom of the stroke, but there's a lot more to fitting a bicycle than this. Your seat position (fore-aft), your stem length and rise, and even your crank lengths will be adjusted by a competent fitter. If you have any indications of knee pain, let the fitter know. Pain on the front of the knee versus back of the knee versus side of the knee all indicate different problems with fit.

    - Warren
     
  9. Jul 20, 2007 #8
    I agree that this is the first thing to do. They additionnaly can provide other advices.

    However, I must say that I learnt my lesson when I bought a bicycle in a mall store. Their incompetence was stunning. I needed a new wheel, and asked the guy in charge if I could use his tools. Of course, for safety reasons, he refused, and told me he would do it. He tried for 15 minutes indeed, and I was the one scared he would hurt himself. I should have explained him how easier it would have been if he did correctly. In the end, I asked a friend at the lab where I can find a real bicycle store, and there it was a totally different story. The guy finished the wheel replacement in like 7 minutes, while chatting friendly with me. He was not even surprised that the other shop's guy was unable to fix the wheel I bought from him.

    I hope for the OP that the store where he bought the bicycle was not in a mall :rolleyes:
     
  10. Jul 20, 2007 #9

    Astronuc

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    No. The leg should be slightly bent at the knee with the pedal at the bottom.
     
  11. Jul 20, 2007 #10

    Moonbear

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    If someone didn't buy their bike at a store (say from a garage sale instead), would they be able to go to a bike shop and have someone do that for a service fee? IF buying from someplace like a garage sale, what basic aspects of fit would one look for to make sure they were buying a bike of the right size for them, which they could then have fit the rest of the way at a shop? Since the OP didn't say where she got the bike from (maybe this came up in another thread I missed that you know it's from a shop), and not everyone can afford to buy a bike new from a shop, this could help those buying second-hand to make sure they don't make a mistake that will leave them in pain or with an unusable bike, especially if money is already tight.
     
  12. Jul 20, 2007 #11

    Astronuc

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    Some bike shops would provide adjustments or repairs on a bike.

    I worked in a bike shop when I was a teenager. In addition to selling and building bikes, we would service and adjust bikes even if the bikes were not purchased at the store.

    I personally went with 26-inch wheels. The seat post tube on my bike is 23" with the seat post at 6". Cranks are 7". My inseam is ~ 31". Basically if one staddles the horizontal bar, one doesn't want to put too much pressure on certain sensitive areas.


    If one wants to get really technical - http://www.coloradocyclist.com/bikefit/

    http://cherry.dcwi.com/cherry/info/fitting.html

    http://bicyclefittingservices.com/ :biggrin:
     
  13. Jul 21, 2007 #12
    I did get the bike new but forget to get them to set the correct height.

    I assume the size of the bike and how much the seat tube is extended are the key questions.

    I found the second website's advice is problematic regarding length of seat tube. It says to multiply .883 with inseam length. But the insearm length is measured with the bare foot. When pedalling one has shoes on and some people may have different shoe thicknesss.

    What I did was go for the basic way which is to put the heel on the pedal and wind it to the lowest part and see the length of the saddle tube when my leg was straight. That is my saddle length because when I peddle it with the ball of feet, there is a slight bent but not much. It feels great now.
     
  14. Jul 21, 2007 #13

    chroot

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    Yes, but it might cost you $30 an hour or so. You might be able to enlist a cyclist friend for free.

    Stand-over height would be the most basic metric. The top tube of the frame needs to be about an inch below your crotch. You should have no discomfort standing over the bike, but you don't want a lot of excess room down there or the bike won't handle well.

    Next, adjust the seat so it's about two inches below the handle bars. This is a pretty normal position for the seat. When sitting on the seat and riding the bike around the block, you should be able to easily reach the handlebars and all the controls (brakes, shifters, etc.) Your leg should be slightly bent at the bottom of the pedal stroke, and your knee should not come up past the handlebars at the top of the stroke.

    If the bike feels decent and handles okay, you're about 90% of the way to a perfect fit. If it feels squirrely, hard to control, or uncomfortable, it might not be the right bike for you.

    - Warren
     
  15. Jul 21, 2007 #14
    Every rider in the TDF has their seat above the handle bars. Some a lot more like Mike Roger's bike. That goes for mountain bikes as well.

    After finding the right seat position and using the alan key to lock it in, would it slip down over time?
     
  16. Jul 21, 2007 #15

    mgb_phys

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    If you have tri-bars, bars sticking out forward from the handle bars, where you rest you elbows on the handlebars then you generally have the seat higher and lean further forward. This gives better aerodynamics.

    Mountain bikes with higher saddle is a bit unusual, you might for fast downhil where you are out of the saddle most of the time anyway.
     
  17. Jul 22, 2007 #16

    Monique

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    :confused: did you test drive the bike? That's the first thing you should do when you test out a new bike to buy: adjust the saddle to your lenght (slightly bend leg, as said) and test ride it.
     
  18. Jul 22, 2007 #17
    I hasn't ridden a bike for over a year so just went with any old height on the low side.
     
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