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  #1  
Old 01-26-2017, 01:05 PM
stephenmarklay stephenmarklay is offline
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Making sense of saddle setback

My road bike is a 73 STA with a 76cm seat height. I have a 25mm setback post and the seat at about the middle of the rails. Running a plumb line it looks like the saddle is about 6-7cm behind the BB.

My commute bike “I think” is also a 73 STA with a 76cm seat height. I have a 20 mm setback post but a different saddle pushed more forward but I end up with a similar measure of 7cm behind the BB.

The oddball is my Salsa EL- Mariachi. That is advertised as a 73 STA but that is effective if anything since it is not straight. I also have a 25mm setback post and the same saddle as my commute bike pushed forward similarly.

The strange part is that the EL-Mar saddle tip is a good 3-4 cm further behind the BB at 11cm.

So to me it sounds like the effective STA on that bike is not as advertised.

Thoughts?
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  #2  
Old 01-26-2017, 01:44 PM
fa63 fa63 is offline
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The saddle is one factor.

On the same bike, the tip of a Brooks Cambium is roughly 2 cm more forward then a Specialized Romin when mounted in the same rail position.
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  #3  
Old 01-27-2017, 09:34 AM
benb benb is offline
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It's a lot easier to get this right (more precise) if you ditch the plumb bob and set the bike up in a corner of the garage/house with the rear wheel touching the wall and the bike propped up vertically.

Measure the distance from the wall to the BB horizontally. (A)
Next measure the distance from the wall to the saddle tip horizontally. (B)

Subtract B-A to get your setback.

This is more precise because the plumb bob method is more affected by the floor not being level. When you use the plumb bob you're measuring the shortest side of a triangle, and if the floor is not level it's changing the length of that shortest side of the triangle so the % error can be fairly large. If you have your tape measure off level when measuring from the wall, or your wall is not true, you're measuring the long side of the triangle, so the % error if the tape measure is not level is smaller. It's also just easier to do with the tape measure as parts of the bike do not interfere and you don't need to hold the plumb bob with one hand and a separate measure with the other hand.

Rail markings are useless unless:
- Exact same saddle on both bikes
- Exact same STA
- Exact same Saddle Height
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  #4  
Old 01-27-2017, 09:36 AM
stephenmarklay stephenmarklay is offline
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Thanks you guys. I will take a look at this more precisely.
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  #5  
Old 01-27-2017, 01:34 PM
nate2351 nate2351 is offline
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Different saddles have different lengths which is worth keeping in mind. I work with a Guru system so in my studio I measure from the center of the rails to the nose of the saddle before I put the saddle on the fit bike Brooks are notoriously long, Specialized as noted are very short. Also the shape of the saddle will change everything as well. I'd venture a guess that if you put a Specialized Power on your bike you would have to completely change the fit.

Fitting between multiple saddles is very tricky and you have to accept the touch points will be different even if the fit feels the same.
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  #6  
Old 01-31-2017, 05:28 PM
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pdmtong pdmtong is offline
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yes, saddles have differing lengths. but thats not sufficient to adequately compare. what you really need to do is align the place where the saddles both flare since that is the one common place for you to be "seated".
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  #7  
Old 02-04-2017, 01:02 PM
ultraman6970 ultraman6970 is offline
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If there was a way to know exactly where the cheek bones are seated in your actual seat in relation to the BB for example, that would be ideal to determine exactly where to put the new saddle at, or at the time to move the position to another bicycle.

With stem and handlebar is pretty much straight forward but with saddles changes a lot because in some saddles you sit further back than other ones, add the length of the saddle, sta differences and the way the bike wants to seat you and you can find yourself dialing saddle height and seatback for months.
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  #8  
Old 02-06-2017, 07:47 PM
giordana93 giordana93 is offline
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Quote:
Originally Posted by ultraman6970 View Post
If there was a way to know exactly where the cheek bones are seated in your actual seat in relation to the BB for example, that would be ideal to determine exactly where to put the new saddle at, or at the time to move the position to another bicycle.

With stem and handlebar is pretty much straight forward but with saddles changes a lot because in some saddles you sit further back than other ones, add the length of the saddle, sta differences and the way the bike wants to seat you and you can find yourself dialing saddle height and seatback for months.
This is spot on. It helps to measure saddle width, and if the saddle has a dip, note where the low spot falls (this can vary with saddle tilt, another reason to start out with level)
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  #9  
Old 02-06-2017, 09:42 PM
ultraman6970 ultraman6970 is offline
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The last time my body changed took me like 8 months to get the saddle height and back right, was insane, before was just this back and this in height, not is just a PITA process Get older and picky hehehe
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  #10  
Old 02-20-2017, 05:23 PM
cykel cykel is offline
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Quote:
Originally Posted by benb View Post
It's a lot easier to get this right (more precise) if you ditch the plumb bob and set the bike up in a corner of the garage/house with the rear wheel touching the wall and the bike propped up vertically.

Measure the distance from the wall to the BB horizontally. (A)
Next measure the distance from the wall to the saddle tip horizontally. (B)

Subtract B-A to get your setback.

This is more precise because the plumb bob method is more affected by the floor not being level. When you use the plumb bob you're measuring the shortest side of a triangle, and if the floor is not level it's changing the length of that shortest side of the triangle so the % error can be fairly large. If you have your tape measure off level when measuring from the wall, or your wall is not true, you're measuring the long side of the triangle, so the % error if the tape measure is not level is smaller. It's also just easier to do with the tape measure as parts of the bike do not interfere and you don't need to hold the plumb bob with one hand and a separate measure with the other hand.

Rail markings are useless unless:
- Exact same saddle on both bikes
- Exact same STA
- Exact same Saddle Height
Great idea, thank-you. I've been trying the plumb bob method for 30 yrs but never thought of this?!
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  #11  
Old 02-22-2017, 04:04 PM
drewellison drewellison is offline
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Stack and Reach

Quote:
Originally Posted by cykel View Post
Great idea, thank-you. I've been trying the plumb bob method for 30 yrs but never thought of this?!
Against a wall is also a great way to measure stack and reach.

Reach = wall-to-centertopofheadtube minus wall-to-bb.
Stack = floor-to-centertopofheadtube minus floor-to-bb.
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