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Saddle-independent set-back measurement?

Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Saddle-independent set-back measurement?

Old 07-20-17, 09:06 PM
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Saddle-independent set-back measurement?

Continuing with my investigation into finding an optimal bike fit, I've been wondering if there is a "saddle-independent" way to measure saddle set-back so that this can be applied to multiple bikes with different saddles.

My interest in this stems from a recent ride in which I became uncomfortable on my Fizik Antares VS saddle after about 50km. Experimentation showed to it was more comfortable when I pushed myself to the rear of the saddle, presumably to align my sit-bones with the widest part of the saddle.

To correct this I moved the saddle forward so that my "natural" position was now towards the rear of the saddle without me having to consciously position myself to the rear.

Of course, this then throws out any set-back measurement based on tip-of-saddle-to-bottom-bracket, which seems to be the usual method. My sit-bones were probably in the same absolute horizontal position as before - I'd just moved the saddle under them.

So, should we be measuring our saddle set-back based on sit-bone position to BB? The makes sense to me, because the relationship should remain constant on any bike. You just find the most comfortable position on the saddle, move the saddle to so that you naturally sit in this spot, then then measure horizontal distance from the sit-bone position to the BB.

The down-side is that it's actually pretty hard to measure exactly where your sit-bones land on the saddle without some kind of memory-gel covering that allows you see where you sit. Either than or a very good friend who doesn't mind touching your derriere :-)
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Old 07-20-17, 09:12 PM
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Measure to the center of the seatpost saddle cradle. You can measure either all the way to the steering axis, or simply measure from the center of the post to the cradle center, which is usually given as the seatpost offset. (seatpost offset + seatpost to steerer axis + stem forward extension = total saddle to bar measurement (to the reference, not to the nose of the saddle)
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Old 07-20-17, 09:15 PM
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Or you could tape a small object onto you seat and by trial and error, find where your sit-bones are.

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Old 07-20-17, 09:26 PM
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I had a Fizik Antares VS saddle and I adjusted it a hundred different ways and I could never get comfortable on it. First you should make sure you have the height of the saddle correct. The best way to find your set back is to adjust your fore/aft so you have knee over pedal. Everyone is different, but I finally gave upon the Fizik and got a Specialized Power Saddle and finally found saddle nirvana.
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Old 07-20-17, 10:12 PM
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One rides bicycles for decades in order to possibly, someday get the saddle position right. The whole point of bicycling is not to get exercise, not to go fast, not to ride long distances and most assuredly not to climb big hills. It is to someday get the saddle position right. When that is accomplished, then you can start working on your bars.

Originally Posted by LAJ
No matter where I go, here I am...
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Old 07-20-17, 11:27 PM
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And the thing is that obviously recumbent riders are doing it totally wrong. Their knees are so far out of the correct position, well it's like they're 90° out of position. It's a wonder their knees don't all fall off. But if they could get their knees in the right position, the bike would be balanced on the front wheel and the drive wheel wouldn't even be touching the ground, so that's not going to work either. Plus whatever they're sitting on, not only is it in the wrong position, it's most certainly not even a saddle.
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Old 07-21-17, 03:06 AM
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You can try to measure from where the saddle is at the widest; it will get you partway there, but you will likely run into saddles where this won't correlate exactly with where you land on the saddle. Alternatively, you can experiment a little, measure the setbacks of the saddles you have from a few different points - from where the saddle is 110 mm wide, or 120, 130... See if there is a stronger correlation from one of those, rather than from the widest point. In the end there will always be some experimentation needed to set a new saddle perfectly, so you decide how much work it's worth in trying to find the best method for the initial setup.
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Old 07-21-17, 04:12 AM
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Saddle shape and length differ so I assume you are looking for a ballpark figure. This is assuming you are using different saddles. If using the same saddle maybe nose to bars would work? I just use the old knee over pedal spindle approximation. Trial and error.
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Old 07-21-17, 10:06 AM
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A little off topic but pretty cool
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Old 07-21-17, 05:21 PM
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https://www.competitivecyclist.com/S...ulatorBike.jsp - of course, it isn't clear what the assumptions are, nor does it take into account individual riding styles.

No matter what, each sizing system is backed by at least one human being. If that human being doesn't take your specific needs into account for whatever reasons, his/(her?) system won't work for you. IOW, if you rely on other people's numbers instead of your own experience, you're very likely to be posting, 'I followed so-and-so's directions to the mm, but I can't ride my bike.'
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