I know in the last couple of weeks, you have posted in response to "how does my fit look" pictures with a pretty basic starting point on seat height and seat fore/aft depending on femur vs. lower leg length. I have just diligently reviewed about 10 pages of posts, but can't find what I thought I remembered you posting, so how 'bout reposting it?
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Re: cerveloguy--basic fitting primer [mr. mike]
[ In reply to ]
Mike, I can't remember which post because there were a few of them but I'll try to give he basics.
If I remember right was that the guy who Tom and I thought was stitting too far forward on a Cervelo P3? I determined that by an imaginary plumbline from his ear which should (according to Cobb's website) disect the elbow joint. The elbow joint should form a 90-110 degree bend of forarm/arm. In this case the plumbline fell thru his forearm ahead of the elbow joint which indicated he was too far forward. Also his elbow angle looked like it could even be a little less than 90 degrees. I measured his femur from midline knee to approx. hip joint and compared that to the length of his lower leg and noted that he was quite a long femur person. He was probably sitting on his P3 at about the max 78/79 degrees which doesn't work for him because of the long femurs. I told him to slide his seat back on the rails 2 cm or more and take another picture. This should, as he slides back, reposition the plumbline from his ear over the center of the elbow joint and also increase his elbow angle. It turns out that this was exactly how the professional fitter had originally set him up on the bike but he had changed it by moving the seat forward thinking he wanted to ride steeper when he posted the picture.
Was that the one you meant? I really enjoy these cyber bike fits. Hope other people post some.
If I remember right was that the guy who Tom and I thought was stitting too far forward on a Cervelo P3? I determined that by an imaginary plumbline from his ear which should (according to Cobb's website) disect the elbow joint. The elbow joint should form a 90-110 degree bend of forarm/arm. In this case the plumbline fell thru his forearm ahead of the elbow joint which indicated he was too far forward. Also his elbow angle looked like it could even be a little less than 90 degrees. I measured his femur from midline knee to approx. hip joint and compared that to the length of his lower leg and noted that he was quite a long femur person. He was probably sitting on his P3 at about the max 78/79 degrees which doesn't work for him because of the long femurs. I told him to slide his seat back on the rails 2 cm or more and take another picture. This should, as he slides back, reposition the plumbline from his ear over the center of the elbow joint and also increase his elbow angle. It turns out that this was exactly how the professional fitter had originally set him up on the bike but he had changed it by moving the seat forward thinking he wanted to ride steeper when he posted the picture.
Was that the one you meant? I really enjoy these cyber bike fits. Hope other people post some.
Re: cerveloguy--basic fitting primer [cerveloguy]
[ In reply to ]
for length of lower leg, do you go midline knee all the way to floor?
Also, there was something about seat height. Distance from center of BB to top of saddle = .883xinseam?
Also, there was something about seat height. Distance from center of BB to top of saddle = .883xinseam?
Re: cerveloguy--basic fitting primer [mr. mike]
[ In reply to ]
Yes, that's how you're supposed to do it. In sock feet, measure from floor to knee midline, actually the space between femur/tibia. For femur measure from knee midline to top of trochanter, (the bump of the hip area which can be hard to find if you have a meaty thigh).
The .883 comes from Greg LeMond's method. Stand in your sock feet with your back against a wall. Place a book tight up against your crotch. Measure from the top of the book to the floor. Now multiply this inseam measurement by .883. This will give you your seat height height if measured from the center of the bottom braket to the top of the saddle along the seat tube.
The .883 comes from Greg LeMond's method. Stand in your sock feet with your back against a wall. Place a book tight up against your crotch. Measure from the top of the book to the floor. Now multiply this inseam measurement by .883. This will give you your seat height height if measured from the center of the bottom braket to the top of the saddle along the seat tube.
Re: cerveloguy--basic fitting primer [cerveloguy]
[ In reply to ]
Some basic bike fit info on this site. It has a photo showing how the inseam is measured.
http://www.coloradocyclist.com/BikeFit/index.cfm
http://www.coloradocyclist.com/BikeFit/index.cfm
Thanks. Best I can tell, lower leg vs. femur are identical. I did drop the seat about 1.5 cm and brought it forward about the same based on those rules of thumb you provided.