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How do I measure seatpost setback?

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How do I measure seatpost setback?

Old 02-23-11, 07:41 PM
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How do I measure seatpost setback?

I want to get a new seatpost and need to know how much setback mine currently has.
How do I measure the current setback?
Thanks.
David
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Old 02-23-11, 08:05 PM
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Center of the post to the center of the clamping mechanism.
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Old 02-23-11, 08:44 PM
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front is a plumb/ vertical line, thru the BB axis,
that way you Include the seat tube angle too..
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Old 02-24-11, 11:14 AM
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So, here is the new dilemma. Now, I know my setback - around 16mm. But I checked the website for Thomson Elite and the one that I need- 27.2mm X 250mm has to be outside of the seat tube for at least 97.5mm.

I measured mine last night and it is only out of the seat tube about 90mm. I can't go any higher. That is as high as my short legs can take it.

I really want to buy a Thomson but I can't tell from the straight seatpost measurements if it would allow me enough fore/aft movement to accommodate my current saddle.

What do you think? Will the straight Thomson Elite 27.2mm X 250mm work for me? The Thomson rep referred me to the diagram on the website but that does not help me.

Thanks in advance.
David
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Old 02-24-11, 12:31 PM
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Originally Posted by Lawrence08648
Center of the post to the center of the clamping mechanism.
That method doesn't take into account the fore/aft size of the clamp. Some posts have very short clamps, so you get more effective setback.
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Old 02-24-11, 12:45 PM
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Forget Thomson, is what you should do, they only make a zero setback post,
Then bend the shaft instead, to get some..

since 27.2 is very common, there are abundant other choices.
American classic are nice,,

Race Face has a nice post, clamps the rails from the sides ,
so newer, low profile race saddles work.
and as the clearance under the saddle bottom side, above the rails,
becomes an issue..
some saddles bottom out on the top of the seatpost.
so you cannot use the front part of the rails..

Want oodles of setback? this is a winner ..
https://www.rivbike.com/products/show...x-250mm/11-048

Last edited by fietsbob; 02-24-11 at 04:30 PM.
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Old 02-24-11, 03:59 PM
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Originally Posted by DGonzalez
So, here is the new dilemma. Now, I know my setback - around 16mm. But I checked the website for Thomson Elite and the one that I need- 27.2mm X 250mm has to be outside of the seat tube for at least 97.5mm.

I measured mine last night and it is only out of the seat tube about 90mm. I can't go any higher. That is as high as my short legs can take it.

I really want to buy a Thomson but I can't tell from the straight seatpost measurements if it would allow me enough fore/aft movement to accommodate my current saddle.

What do you think? Will the straight Thomson Elite 27.2mm X 250mm work for me? The Thomson rep referred me to the diagram on the website but that does not help me.

Thanks in advance.
David
how much setback do you need? what is your budget?
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Old 02-24-11, 05:16 PM
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I don't really know how much setback I need. I have attached a picture above. I believe my current setback is 16mm which I don't think is much. Now that I look at my bike I realize that the seat tube is slanted naturally. I am wondering if a straight seatpost will do as long as I can tilt it forward a bit.

I am interested in Thomson because of the ability to fine tune it.

As far as a budget, I am happy to buy used for less than a $100.
Thanks.

Last edited by DGonzalez; 02-24-11 at 05:16 PM. Reason: add words
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Old 02-24-11, 05:51 PM
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Many other saddle clamps may be fine tuned , 2 different screws in opposition to each other
Dozens of makers have a model thart do that.

is how many have sorted this out ,
not being a gram counter, I have a 3 piece kit on my bike,
the saddle adapter pin on top of a common seatpost , and a saddle adapter
lets me set setback as an adjustment .

the 2 parts from Brompton do this for me ..
Even of you got the premium seat pin from Rivendale.. sub $100
[Kalloy comes in $20 less]
https://www.rivbike.com/products/show...2-x-270/11-077
and the 2 other Brompton parts
https://www.foldabikes.com/CloseUp/bike/sapMain.html
https://www.foldabikes.com/PriceListH...pentaclip.html
pentaclip can be fine tuned in angle and saddle rail height , offering 2 positions.

then setback distance is an adjustment not a product choice..

Last edited by fietsbob; 02-24-11 at 06:00 PM.
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Old 02-24-11, 06:24 PM
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Originally Posted by fietsbob
Many other saddle clamps may be fine tuned , 2 different screws in opposition to each other
Dozens of makers have a model thart do that.

is how many have sorted this out ,
not being a gram counter, I have a 3 piece kit on my bike,
the saddle adapter pin on top of a common seatpost , and a saddle adapter
lets me set setback as an adjustment .

the 2 parts from Brompton do this for me ..
Even of you got the premium seat pin from Rivendale.. sub $100
[Kalloy comes in $20 less]
https://www.rivbike.com/products/show...2-x-270/11-077
and the 2 other Brompton parts
https://www.foldabikes.com/CloseUp/bike/sapMain.html
https://www.foldabikes.com/PriceListH...pentaclip.html
pentaclip can be fine tuned in angle and saddle rail height , offering 2 positions.

then setback distance is an adjustment not a product choice..
Thanks. I never knew that existed.
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