why use a Set Back Seatposts ?

[cnighbor1]

what is the idea behind a Thomson Masterpiece Setback Seatpost 27.2 x 240mm Or any setback Seatpost
doesn't the use of one indicate top tube on the frame is too short for that rider? or stem is too short?
I can't really figure out why the need of a set back Seatpost
thoughts
Charles

[Mzilliox]

Hey Charles, I used to wonder the same thing.
Here is my take, and im not sure how accurate it is, so take it with many grains of salt.

1. Setback seatposts i have heard are more comfy and absorb shock better...
2. From a geometry standpoint, you dont want too slack of a seat tube for a few reasons, but mainly to keep the wheels where they should be, and the rider's front center where it should be. but some riders still require being further behind the bottom bracket, so a bit of setback allows the rider to get in the correct position with regards to the bottom bracket. some riders do not require that, some riders do. I know that from riding different bikes i like a seat angle of 73-74 degrees. but to put me in the right place with regards to the bottom bracket, i need a touch of setback.
3. a set back seatpost should NOT be used to alleviate fit issues such as reach... as moving it for this purpose will put the rider in the wrong position for optimal pedalling.

[ripvanrando]

Seat angle is too steep for proper bike fit that gives the rider balance.

Few modern non-custom bikes that I have ridden would work for me without a setback post

[ripvanrando]

He explains it better.....but it is about balance and comfort for me

https://www.stevehoggbikefitting.com...or-road-bikes/

[rwsaunders]

"My eyes refuse to watch them, maybe I'm too old?" Dario Pegoretti referring to non-setback seatposts.

[Luwabra]

upon my paid for "pro fit" we discovered that my femurs are way longer than the norm. so my reach is good but my knees were killing me bc I couldn't get the placement of the saddle where it needed to be. I suppose I could get longer crank arms but I can achieve the correct kops ish placement with a setback post. not that KOPS is a concrete placement but its pretty damn close to where he put me without using a plumb bob or anything. I don't know if this is right or not but its the way i achieve comfort as in no Knee pain. even with a setback post my saddle is usually slammed all the way aft.

??? .....following this thread.

[hampco]

Historically, many saddles sat further forward than modern saddles do - take a look at a Brooks Pro to see a good illustration of this. So a setback post would get the rider where he needed to be without an overly-slack seat tube angle, which introduces its own set of problems.

So it's partly an anachronism that we still use them - like nipples on males - and partly aesthetics, as they look correct on a road bike.

[nooneline]

Originally Posted by cnighbor1

what is the idea behind a Thomson Masterpiece Setback Seatpost 27.2 x 240mm Or any setback Seatpost
doesn't the use of one indicate top tube on the frame is too short for that rider? or stem is too short?
I can't really figure out why the need of a set back Seatpost
thoughts
Charles

the purpose behind a setback seatpost - which is a very ordinary bike part - is to get the relationship between the hip and the bottom bracket where it ought to be.

nobody says that you have to choose a bike with a seattube angle that lets you use a straight seatpost. you could just as easily be asking "doesn't the use of a no-setback seatpost indicate a top tube or stem that is too long?" but either way it would be the same moot point, since nobody should use seatposts (or saddle position, essentially) to handle reach issues - those can be adjusted with things that don't so directly affect your pedaling.

think of seatpost choice as doing to your pedaling what stem length does for reach - affords you a measure of adjustability. you size your bike, and you refine your position with other adjustable choices: seatpost, stem, handlebar, crank length.

[ergott]

Use whatever seatpost you need to center the rails (more or less) and achieve this.

http://kirkframeworks.com/2009/06/19/riding-tip-3/

For me that's a setback seatpost with typical bikes my size.

[David Kirk]

I think it's possible that many are reading too much into this.

Way back in the day high quality posts were designed with setback because it was simply easier to package the clamping hardware behind the post and not on the post centerline.

Once that was done most frames were designed to work with a traditional setback post....and in line with this saddle rail design was tied to a setback post.

The important part is that each rider has three contact points and those points relate to each other in a certain way. Within reason it doesn't matter how those dots are connected and if one is designing a frameset to fit a given rider either type post, setback or non-setback, can be made to work.

dave

[palincss]

Originally Posted by cnighbor1

what is the idea behind a Thomson Masterpiece Setback Seatpost 27.2 x 240mm Or any setback Seatpost
doesn't the use of one indicate top tube on the frame is too short for that rider? or stem is too short?
I can't really figure out why the need of a set back Seatpost
thoughts
Charles

You would need a setback post in order to get the saddle to the proper position vis a vis the bottom bracket. Different saddles have rails of varying lengths, and frames have varying seat angles. With a short-railed saddle like a Brooks or Berthoud, I need both a setback post like a Nitto S83 and a seat angle of between 71 and 72 degrees to get my saddle to the proper position for me; with a 73 degree seat angle I need a seat post with a lot of setback like a Nitto S84.

Since these factors describe every bike I've ever owned, what I can't understand is the use for a zero offset post.

[KidWok]

Originally Posted by David Kirk

The important part is that each rider has three contact points and those points relate to each other in a certain way. Within reason it doesn't matter how those dots are connected and if one is designing a frameset to fit a given rider either type post, setback or non-setback, can be made to work.

dave

Agree with this. Found this recently on Open Cycles' website about their U.P.:

Zero-setback seattube
With a minimalist 27.2mm diameter we maximize the flex in our seatpost & seattube. This is especially a big plus on rough terrain. The seattube angle is designed around the use of a straight, zero-setback seatpost rather than a regular seatpost with setback (we’ve never understood those). Zero-setback posts are lighter, saving you another 10-30 grams (every little bit helps and you can then put that saved weight into a 500g saddle like the Brooks!).

I find it weird that a production bike company went so far as to take a stand on this. Why say anything about this when fit is specific to rider's measurements?

FWIW...most of my bikes are around a 73-73.5 STA and I'm using setback posts that have ~1.5cm offset. I have a Lemond MJ Spline that uses a straight post with the saddle pushed all the way back to get the same position because it has a 72.5 STA.

To the OP's point though, the Thomson setback post is ugly. It sticks out like a sore thumb on any bike I've ever had it on.

Tai

[saab2000]

Originally Posted by hampco

Historically, many saddles sat further forward than modern saddles do - take a look at a Brooks Pro to see a good illustration of this. So a setback post would get the rider where he needed to be without an overly-slack seat tube angle, which introduces its own set of problems.

So it's partly an anachronism that we still use them - like nipples on males - and partly aesthetics, as they look correct on a road bike.

This is pretty much true. Modern saddles have longer useful rail sections. I use 20+ year old Selle Italia Turbomatic saddles on several of my bikes and they pretty much require a setback post and to have the saddle slammed all the way back.

On a few other bikes I use Fizik Arione saddles and they're pretty much centered, though still with some setback on the seatpost itself.

And yes, aesthetically a setback seatpost looks appropriate in most applications. Vanity is a great thing.

[Climb01742]

Since many of us buy frames used, getting our saddles where they need to be requires different post setbacks. Setback is just a tool to get our butts where they belong. And whether a zero setback post looks good or not tends to depend on the totality of the bike, not simply the post.

[drewellison]

Because Eddy used one.