# Custom Seat Post Manufacture or Change?



## sciencegeek (Apr 10, 2008)

My dilemma:

I have an 08 Specialized Stumpjumper FSR Expert; I would like to put the seat back further. My current seat post has 25 mm setback, which appears to be the maximum commercially available setback for a post with 30.9 mm diameter.

I'd either like to change my current post to have more setback, or get a custom manufactured one with 2" of setback.

Any ideas? Anyone here who could do this?

TIA


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## Kavik (Apr 13, 2007)

shot in the dark...Find cool LBS with a QBP catalog. They should have either a post or a shim to get you to 27.2 or something common.


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## Walt (Jan 23, 2004)

*Shim and I-beam saddle/post*

The I-beam saddles (SDG, Kore, and a few others make seats and posts) allow a LOT more fore-aft adjustment, so you could get a shim to 27.2 and use one of those.

That assumes you like the saddles that are available for the system, of course. It's a great setup (light, strong, not too pricey) but the selection of saddles is fairly small. I imagine you can get the saddle a bit further back with such a setup, and in fact my BTI catalog shows a 30.9 post as well, so you wouldn't even need a shim. I've only built up one bike with that setup, though, so it would be worth finding some stuff to measure to make sure the seat will go back as far as you want.

-Walt


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## donk (Jan 28, 2004)

No personal experience, but if money is no object bold precision makes custom offset posts.

http://www.boldprecision.com/bicycle.htm


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## sciencegeek (Apr 10, 2008)

*thanks guys*

read up on those I-beams ... sound too painful for my old behind.

and I did find bold precision over the weekend (they make some nice stuff), and communicated with the owner. he said he's always wanted to try bent posts as opposed to welded ones so he might give it a go. keeping my fingers crossed he can figure out how to work that titanium without weakening it!


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## pvd (Jan 4, 2006)

I tried an I-beam saddle once. The most painful thing I've ever experienced. absolutely no flex.

2" is a lot of setback. Are you sure that this bike fits you? Getting too far back on MTB is inefficient, but also causes huge problems while climbing and decending. What kind of KOPS and leg angle are you getting right now?


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## EnglishT (Apr 9, 2008)

Echo what PVD says... if you need that much extra setback, I would have to question whether the frame fits you.


I-Beam is a good way to get a lot of offset, but you are limited in saddle choice, and it is quite stiff.

In fairness that would matter more on a hardtail, but it does make a difference whatever you ride.


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## Blahla (Mar 3, 2006)

*Titec hellbent*

Pricepoint has the titec hellbent you can use with a shim.


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## sciencegeek (Apr 10, 2008)

@ blahla: thanks for the tip ... but I think I don't want a big shim like that.

@ pvd and ET: yeah, i understand your comment about size but the bike fits ... it's just that I want to keep my fairly short stem up front. I'm a pretty competent climber but when the nose points down I sometimes feel my butt could be a tad lower and further back.

The thing about the 08 Stumpjumper FSR is that it has a long wheelbase and the 'extra' length is in the back (from bottom bracket to rear hub). It's pretty interesting to compare it to the 08 Enduro, which has a slightly longer wheelbase than the SJ, with the same rear-hub to bottom bracket distance, and more bottom-bracket to front hub distance. Anyway, I just feel like my perfect positioning on that bike would be just a bit further back. An XL would have been too big for me.


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## EnglishT (Apr 9, 2008)

sciencegeek said:


> @ pvd and ET: yeah, i understand your comment about size but the bike fits ... it's just that I want to keep my fairly short stem up front. I'm a pretty competent climber but when the nose points down I sometimes feel my butt could be a tad lower and further back.


You descend seated?

Almost all descents ill do standing, for which reason I have the saddle quite far forward - which is good for seated climbs and allows me alot of space to ride off the back (if needed) when going down.


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## sciencegeek (Apr 10, 2008)

yeah when it gets technical my butt is off the seat of course ...


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## pvd (Jan 4, 2006)

Again...



pvd said:


> What kind of KOPS and leg angle are you getting right now?


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## SuspectDevice (Apr 12, 2004)

A bike either fits, or it doesn't fit. Can you post up a picture of the bike as you have it setup now, and maybe one of you on it? It sounds to me like there is some other hitch in yer giddyup, and I am guessing it might be the suspension setup, but it could be something else... 

Unless... Do you ride XC on flat pedals?


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## rockyuphill (Nov 28, 2004)

sciencegeek said:


> yeah when it gets technical my butt is off the seat of course ...


You should consider trying a Crank Bros Joplin post. Being able to lower the seat by 3" on the fly gives you more room to get your butt lower and further back on steep descents and makes it less likely that the nose of the seat will use your nards as a punching bag. Then the seat is always in the right place for climbing and riding flats.


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## sciencegeek (Apr 10, 2008)

guys. it's about the 08 SJ geometry and my preference for a stem that's not too long.
here's a picture of the bike.
note how the seat tube swings forward above the BB and then backward and up.
the result of that geometry is that the seat is further forward than on most bikes.
drop a line down from the seat, you'll see what I mean.
I want my ass further back, that's all there's to it.


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## EnglishT (Apr 9, 2008)

sciencegeek said:


> guys. it's about the 08 SJ geometry and my preference for a stem that's not too long.
> here's a picture of the bike.
> note how the seat tube swings forward above the BB and then backward and up.
> the result of that geometry is that the seat is further forward than on most bikes.
> ...


Well... Toptube length is one of the most important aspecs of fit - if the cockpit length doesnt work, well its not the right size/design for you imho - a massive layback will potentially mess things up with where your weight is for climbing, and definately reduce efficiency. 
Personally with a shorter stem, I accept a shorter cockpit because if you move back the saddle you are moving more weight back (off the front wheel) which causes problems with front wheel traction (especially climbing). And at the same time, shorter stems are normally chosen for their qualities on descents - having the seat forward more allows more space to ride off the back of it (when needed) more comfortably on those descents where its needed and to keep weight forward for seated climbs - to move it back will restrict things a little more both descending and ascending.

Excuse me if its the picture but... I dont see anything unusual about the position of the saddle... It doesnt look drastically "further forward than on most bikes" to me - it looks about normal for a trailbike.

Its a trailbike rather than a full on XC race bike, so the position is bound to be a little more relaxed/upright - trying to get it longer by using a post with massive layback is gonna cause problems with weight distribution, while reducing efficiency... But if its so small that its cramped, you were sold the wrong size bike.


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## D.F.L. (Jan 3, 2004)

The '08 stumpy has a 75 degree effective SA.


That's why the OP and others want more setback. Legitimate desire.


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## Thylacine (Feb 29, 2004)

Even sagged I reckon you'd still be too far forward.

Who want's to look like a dog humping a football when they're riding along?

I think there's two ways to get more setback without going with a custom post:

• There's an FSA post with a massive amount of setback, although I can't seem to see it on their website. You could use that with a shim.
• SDG now has an i-beam saddle with a cutout to let the seat flex, that might be worth a try. Their post is also available in 30.9, too.


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## rockyuphill (Nov 28, 2004)

The FSA K-Force carbon post has 32mm of setback.


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## PuddleDuck (Feb 14, 2004)

Two manufacturers will make a custom length and setback Ti post for you. I don't know if they'll do a 30.9, but they definitely do 27.2's

Black Sheep.
Kent Eriksen.

Good luck.


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## scooter916 (Jan 2, 2006)

check out the AC postman, I think they only make 27.2mm but a 27.2-30.9mm shim is very common.

http://images.google.com/imgres?img...mponents&um=1&hl=en&client=safari&rls=en&sa=G


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## swift (Apr 3, 2007)

By observing how high you are running your seatpost, I'm thinking you may do well to go for the next largest frame size. It may even be a cheaper option than having a one-off seatpost made.

Good luck!


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## PuddleDuck (Feb 14, 2004)

swift said:


> By observing how high you are running your seatpost, I'm thinking you may do well to go for the next largest frame size. It may even be a cheaper option than having a one-off seatpost made.
> 
> Good luck!


Unless the seat angle is slacker on the larger size the need for increased setback will still be there....


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## buckoW (Feb 7, 2007)

shim with a Thomson layback post or that SDG Formula FX seat is comfy (i have one) but I wouldn't want to run it all the way back on the plastic.


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## Team Fubar Rider (Sep 3, 2003)

Thomson's setback is only 16mm. FSA offers their K-Force with up to 32 mm of setback, but it is only in a 27.2mm diameter. Once you shim it up it will only be just a hair over 30mm of set back (since this line is measured from the center of the post and you have changed the effective diameter of the post).

Honestly, I don't think you'll find anything much bigger than this. If you start getting the post setback much further, you'll start putting too much load at an angle that the post can't handle. If you need anything more than 25-30mm, I would agree your frame is too small.


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## k0y0te (Oct 29, 2006)

I've run into the same problem on more than one bike. titec hellbent is the way to go. 1.5" setback. 

the problem is, they are getting harder and harder to find. I don't even see them on the titec website anymore. I've picked up several on ebay over the years. finding a 30.9mm may be tough.


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## D.F.L. (Jan 3, 2004)

Team Fubar Rider said:


> Thomson's setback is only 16mm. FSA offers their K-Force with up to 32 mm of setback, but it is only in a 27.2mm diameter. Once you shim it up it will only be just a hair over 30mm of set back (since this line is measured from the center of the post and you have changed the effective diameter of the post).
> 
> Honestly, I don't think you'll find anything much bigger than this. If you start getting the post setback much further, you'll start putting too much load at an angle that the post can't handle. If you need anything more than 25-30mm, I would agree your frame is too small.


Setback is measured from the CENTER AXIS of the post, so diameter would have no effect on amount of set-back. The post could be 4 FEET in diameter, have 30mm of setback from the post axis, with the clamp within it's own diameter... and still have 30mm of set-back... could be wrong on that... in other words, post diameter should have no effect on set-back.

Also, scroll up and read about this frame having a 75-ish degree SA...


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## Team Fubar Rider (Sep 3, 2003)

D.F.L. said:


> Setback is measured from the CENTER AXIS of the post, so diameter would have no effect on amount of set-back.
> 
> Also, scroll up and read about this frame having a 75-ish degree SA...


Um, yeah, I know, that is why I said it was measured from center of the post. If the post I mentioned is a 27.2 and it is getting shimmed into a 30.9 you're losing 1.85mm of setback. (30.9-27.2 = 3.7mm. 3.7mm /2 = 1.85mm) Of course if it was a 30.9 post it would not have an effect on the setback. So I am thinking YOU should go back and read...

And as other posters have mentioned, if you're needing almost an inch and a half of setback to get the frame to fit right, it probably didn't fit right to begin with...


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## D.F.L. (Jan 3, 2004)

That would be right of your shims were somehow off-center.

Please explain so a dumb-as s like me can understand how a shim can affect post offset, keeping in mind that set-back is measured from the centerline of the post and that every shim commercially available keeps a post on-center.

The horizontal difference between a 73 and 75 degree angle on a frame of that size is significant. Seen many 75 degree SA bikes, lately? (sometimes, people with long femurs will require 72 degree (or less) SA, sh it happens)

Again, you could have a seatpost with a 4 MILE diameter, and if the clamp's center is 30 MILLIMETERS behind the centerline of that 4 mile diameter post, the setback is still 30mm.

Same thing applies for a seatpost that is 4 LIGHT YEARS diameter: still 30mm set-back.

Help me out here.


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## Thylacine (Feb 29, 2004)

I love teh Intarweb.


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## pvd (Jan 4, 2006)

This thread sucks.

Buy a bike that fits for crying out loud.


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## EnglishT (Apr 9, 2008)

pvd said:


> This thread sucks.
> 
> Buy a bike that fits for crying out loud.


Could it be any better said?

No I dont think so.

Its crazy how people are trying to justify forcing a bike to fit, when the OP (seemingly) bought the wrong size in the knowledge that it didnt fit right.
Look its kinda simple - if the bike doesnt fit you then you dont buy it. If there is no size that you can get to fit you (with sensible component choices), then you look at other bikes from other manufacturers that do. I know there are alot of fanboys around (and not just for Specialized) but the honest truth is that if it doesnt fit, you shouldnt buy it just because its a brand you like (im not saying it neccessarily was in this case, but its far from unknown for people to buy a brand without even considering if its the right choice) - "making" it fit by using ridiculous offsets or overly long/short stems is just a recipe for something that doesnt quite work how you want it to.

I really dont understand why OP didnt just buy a bike that fit in the first place.


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## wildtrekker (Sep 2, 2008)

Don't know if this helps but chk out this link:

http://www.descent-world.co.uk/index.php?option=com_content&Itemid=82&task=view&id=910

you might find this interesting.


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