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Is there a "standard" saddle setback for each frame size?

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Is there a "standard" saddle setback for each frame size?

Old 09-14-17, 06:22 AM
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Is there a "standard" saddle setback for each frame size?

I've been looking at set-back on my bikes and trying to work out what suits me.

I've noticed that there seems to be a lot of variation in setback between frame sizes, even if the saddle is placed in the middle of it's fore-aft adjustment range.

For example on my medium (c. 54cm) Giant TCX, setback from tip of saddle to BB is about 6cm with the saddle in middle of the rails. On a 56cm Specialized Roubaix, the set-back is 68mm with the saddle almost all the way forward - it would be at least 80mm with the saddle in the middle. This seems like a fairly large difference between "adjacent" frame sizes.

So I'm wondering whether the difference in frame size, e.g. 2cm between 54 & 56cm frames is reflected exactly in median setback?

I realize that saddle profile could have an effect here, so maybe there isn't a "rule" in effect. I have access to a 58cm frame which I could measure to test the hypothesis.

Any thoughts?
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Old 09-15-17, 11:10 AM
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I don't think there is a standard saddle setback method but there is a starting point. That point is with the front of the knee directly over the pedal spindle. If that position turns out to be best for anyone it would be sheer coincidence. If, from that saddle location, there is judged to be excessive weight on hands, the saddle should be moved back. Generally, the cyclists position is optimized for comfort for a purely recreational rider or more toward performance and getting power to the pedal for one who races.

In my case, I'm a card carrying old guy and am interested almost totally in comfort. To get more weight off the hands I've installed a seat post with extra setback. This has worked out well with a noticeable improvement in comfort. I do notice though, that if I'm having a good day, I slide forward on the saddle and reach out to the ends of the hoods which gives me a longer and lower position.

Saddles vary in length. Some are well longer than others so that measuring a position from the tip seems to me to be too imprecise. I measure from where I judge the sit bones are situated on the saddle. I figure this is the widest point of the saddle and should be quite accurate for any saddle. Road Positioning Chart | Park Tool I record all relevant measurements on the Park Tool Positioning Chart for future reference. I have these charts going back about 5 years. I find it instructive to compare positions over time.
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Old 09-18-17, 07:03 PM
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Originally Posted by johngwheeler
I've been looking at set-back on my bikes and trying to work out what suits me.

I've noticed that there seems to be a lot of variation in setback between frame sizes, even if the saddle is placed in the middle of it's fore-aft adjustment range.

For example on my medium (c. 54cm) Giant TCX, setback from tip of saddle to BB is about 6cm with the saddle in middle of the rails. On a 56cm Specialized Roubaix, the set-back is 68mm with the saddle almost all the way forward - it would be at least 80mm with the saddle in the middle. This seems like a fairly large difference between "adjacent" frame sizes.

So I'm wondering whether the difference in frame size, e.g. 2cm between 54 & 56cm frames is reflected exactly in median setback?

I realize that saddle profile could have an effect here, so maybe there isn't a "rule" in effect. I have access to a 58cm frame which I could measure to test the hypothesis.

Any thoughts?
In a word, no.

I think saddle setback should be about the same for every bike you ride which are of the same style. It's based on setting up comfortable and efficient pedaling. The way your legs like to work is based on your skeletal and muscular makeup, not the length of the seat tube.
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Old 09-18-17, 07:42 PM
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Originally Posted by Road Fan
In a word, no.

I think saddle setback should be about the same for every bike you ride which are of the same style. It's based on setting up comfortable and efficient pedaling. The way your legs like to work is based on your skeletal and muscular makeup, not the length of the seat tube.
Thanks. I understand that an individual will have a small range of set-backs at which they are both comfortable and efficient, and that this will vary for each person.

My question was more about the range of set-backs that are possible for a given frame size. The larger the frame, the larger the set-back at the mid-point of the saddle rails (assuming the same saddle height) due to the seat-tube angle.

Edit: I found some references to a Greg LeMond book in which he lists suggested frame size and set-back based on the rider's cycling inseam. My 875mm inseam aligns with recommendation for a 6-8cm set-back and 56-57cm frame - which is pretty much what I have.

So on my 56cm Endurance frame, I can't easily achieve the same 60mm set-back that I have on my medium / (approx 54cm) CX frame. At least not without a zero-offset seat post, which may not even be available for the proprietary off-round carbon seat-post on my bike.

I find it awkward to find a good fit because I have a long-for-height inseam which leads me to larger frames to get a reasonably small saddle-to-bar drop. But then I often have to push the saddle all the way forward to get a comfortable set-back.

So it seems that set-back is something that is assumed to increase as the bike (and by extension the rider) gets larger. There's only about a +/- 2cm adjustment on most saddles (from the mid-point), so this would appear to imply that there is a assumed ranges of set-backs that are possible on any given size.

Last edited by johngwheeler; 09-18-17 at 08:16 PM. Reason: update
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Old 09-18-17, 07:49 PM
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Not that I can find, but when you find your perfect spot---a sharpie is your friend...mark the seat rails, mark the post, mark the angle-so you can take it off if need be and get it back to the same place. My $0.02.
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Old 09-19-17, 03:00 PM
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If by set back you mean measuring from a plumb line thru the BB, to the center line of the angled seat tube, the horizontal distance line ,

would be longer , if the seat tube angle is is the same but longer...



...
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Old 09-19-17, 03:41 PM
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Originally Posted by fietsbob
If by set back you mean measuring from a plumb line thru the BB, to the center line of the angled seat tube, the horizontal distance line ,

would be longer , if the seat tube angle is is the same but longer...



...
Good point. I'm measuring set-back from BB to tip of saddle (somewhat imprecise because of saddle design differences, I know).

However, I think I'm also assuming that saddle height, and therefore horizontal position, increase with frame size, but of course, this isn't necessary the case! Given the same STA and position on the saddle rails, the saddle at the same height (from the BB) would have the same set-back on any sized frame, right?

So....possibly answering my own question, it seems that "median" saddle setback is determined primarily by a combination of STA and saddle height, the latter of which is determined largely by the rider's inseam length.

Sorry if my question was a stupid one! Your answers did make me think about it some more though!
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Old 09-19-17, 03:51 PM
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More thigh than overall leg length..
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