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how do i measure femur length?(9 posts)

how do i measure femur length?colker
Jun 28, 2002 2:39 PM
btw. what's should be the "average" length on a 5'9" guy? tnxs
re: how do i measure femur length?Pecos
Jun 28, 2002 3:29 PM
Most say to sit erect against a wall and measure from the wall to your knee joint.
I hope this isn't to determine crank length!Kerry
Jun 28, 2002 3:56 PM
You will find no high quality data to support any particular crank length as being better than any other. This is true whether or not you correct for leg length, femur length, etc. What little research has been done on crank length suggests that people adapt to different crank lengths and there is no optimum or formula related to body proportion. On the other hand, you will find lots of anecdotal or low quality data to support all kinds of conclusions, and more theories than you can shake a stick at. A rider's response to changes in crank length is 1) highly individual, 2) dependent on riding style and the event (TT, climbing, crits, track racing, etc.), and 3) most important, highly adaptive. This is why it is so hard to study the effect of crank length.
Are you ready for analysis paralysis?Nessism
Jun 28, 2002 6:35 PM
Check out the following link:

http://www.bsn.com/Cycling/ergobike.html

Good luck.

Ed
been there...colker
Jun 29, 2002 5:12 AM
done that. those theories make sense to me(long armed x long torso determining different bike fit).
i ride a 1cm bigger bike than my inseam suggests and even then i push the saddle back and ride on a 12 cm(went back to 12) stem.i have been on a 13cm. bars are 7cm below saddle.
i'm obsessed with bike fit and toy with the idea of a 53cm frame but i wonder if i would like a 74º seat angle.
confused???C-40
Jun 29, 2002 11:28 AM
Frame size has nothing to do with saddle position. It's the seat tube angle ans seat post design that are important. The seat post design affects the amount that the saddle can be moved back. If you have a "straight-up" like a Thomson, the clamp design severly restricts saddle movement, effectively increasing the seat tube angle by 1.5 degrees.

Also, if you push you saddle all the way back, is this to get the knee located in a particular location relative to the pedal spindle (the correct way) or an attempt to increase the reach to the bars (which is the wrong approach)?

If you want to reduce frame size to increase standover clearance or lower the bars in relation to the saddle, that's fine, but you should not have to increase the seat tube angle, just to reduce frame size. Either select a different brand with less angle, or get a seatpost with more setback. Just remember that as the saddle is moved back, the stem must be shortened to maintain the same reach.
waste of time...C-40
Jun 29, 2002 11:46 AM
It's extremely difficult to measure from the center of the knee joint to the center of the hip joint, with any accuracy.

What would be the point? All you need to know for bike fit is the combination of seat tube angle, seatpost and saddle type that will allow you to attain the optimum knee position relative to the pedal spindle. The optimum position being the one that produces the most power for the duration and type of terain that you intend to ride. This is best determined by riding a real bike. The position that is optimum for a short flat course won't be the same as the best position of a long hilly one.

My saddle rails have a scale marked on them that allows me to fine tune position for the terrain. I would move the saddle back .5 to 1cm for a hilly (or windy) ride, or forward by the same amount for a flat course.
waste of time...colker
Jun 29, 2002 12:33 PM
move mine + /- 0.5cm too.
xray to scale nmDougSloan
Jun 30, 2002 11:10 AM