# zero offset seatpost - advantages?



## BigSur

Always wondered why riders, or which kinds of riders, choose a seatpost with a zero offset. Are there any specific advantages? And doesn't a zero offset throw off the geometry of a bicycle that's manufactured with a seatpost with offset??


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## wim

*One reason.*

Some riders (especially those with short femurs) shove their saddle all the way forward to achieve what they believe to be a proper position over the bottom bracket. For these riders, a zero-offset seat post makes sense. With the saddle at the same position over the bottom bracket, the zero-offset post would clamp their saddle around the middle of the rails instead of at the very ends of them.

Add-on, for what it's worth: I don't think clamping a saddle at its rail ends is really a problem other than having zero adjustment options in one direction.

/w


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## C-40

*info...*

There is no advantage to a zero setback seatpost for a road bike. Fewer people all the time take any stock in the idea that femur length and the resulting knee over pedal measurements are relevant to producing the proper rider position. It's better to have the rider properly balanced over the saddle and ignore KOP. Achieving a good weight balance nearly always requires a setback seatpost, to move the saddle back and reduce weight on the riders hands.

I found that moving my saddle back not only improves comfort, but also allows me to tolerate more saddle to handlebar drop. I've increased the drop on my bike from 9.5cm to 11.5cm with the saddle about 2cm further back. Depending on the saddle, I need a 25-35mm setback to get the position I want. Even then, the saddle will be most of the way back.

Using a zero setback post instead of the more common 20-25mm moves the clamp forward about as much as a 2 degree increase in the seat tube angle. I've used one once, but it was on a older LOOK frame with a slack 72.5 degree STA. It positioned the seat rail clamp in the same location as a newer frame with and 74.5 degree STA and 25mm setback post. 

Zero offset posts are really best suited to MTBs that have slack STAs.


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## wim

C-40 said:


> Fewer people all the time take any stock in the idea that femur length and the resulting knee over pedal measurements are relevant to producing the proper rider position. It's better to have the rider properly balanced over the saddle and ignore KOP


I certainly agree with that. As a matter of historical interest, old training bibles explained what's now known as KOPS as a means to achieve that exact proper balance you talk about, never as a means to position the rider for maximum force generation. Perhaps something got lost in translation?


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## CleavesF

You can offset a Zero with a longer stem. Just like you can get shorter crankarms and increase your seatpost height. 

Zero is good for those that don't need the long "virtual top tube".


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## Andrea138

I use a zero offset seatpost because I've got short femurs, and I need it to get my knee anywhere close to KOPS. Yes, I know that's not the end-all you-gotta-be-there position that it used to be touted as... I mean, with a setback seatpost, even with the saddle all the way forward, I'm a few centimeters behind, and it makes my knees hurt like crazy.

//Yes, I've seen a qualified fitter


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## brblue

With a flexy saddle shell, the rails tend to bend if the rider is heavy enough, bend caused by the ends of the rails being pulled towards each other.
Having your saddle clamped at one of the extremities will cause the saddle to raise it's "tail" section while rails are bent (and rails clamped at their front) or to raise it's nose while rails are bent (and rails are clamped at their mst rearward position)

I'm not saying any of these acase is good or bad, I'm just saying that changing seatposts can lead from clamping your saddle's rails at their end to clamping them at their front, thus producing different saddle feel while actually with no rider on, the saddle is in the same position and tilt towards bottom bracket as before. Again, something to cope with if changing seatposts.
I guess the impact is minimal / non existent with saddles with stiff shells / rails..

good luck
br


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## MShaw

C40's obviously pretty close to 'standard.' I'm not. I've got short legs and a long torso. To get a bike that fits front to back, I've gotta ride something bigger'n my legs can handle, so I'm WAY far behind the BB unless I get something with less setback. 

Compact bikes have been a doGsend for me! Get the length I need, but with standover I can live with. :nod

YMMV according to YOUR specific fit needs. 

M


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## andulong

By using a zero setback post on bike with a slack seat tube you can achieve the same setup as a bike with a steep seat tube and a normal setback post.


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## Nessism

C-40 said:


> There is no advantage to a zero setback seatpost for a road bike. Fewer people all the time take any stock in the idea that femur length and the resulting knee over pedal measurements are relevant to producing the proper rider position. It's better to have the rider properly balanced over the saddle and ignore KOP. Achieving a good weight balance nearly always requires a setback seatpost, to move the saddle back and reduce weight on the riders hands.
> 
> I found that moving my saddle back not only improves comfort, but also allows me to tolerate more saddle to handlebar drop. I've increased the drop on my bike from 9.5cm to 11.5cm with the saddle about 2cm further back. Depending on the saddle, I need a 25-35mm setback to get the position I want. Even then, the saddle will be most of the way back.
> 
> Using a zero setback post instead of the more common 20-25mm moves the clamp forward about as much as a 2 degree increase in the seat tube angle. I've used one once, but it was on a older LOOK frame with a slack 72.5 degree STA. It positioned the seat rail clamp in the same location as a newer frame with and 74.5 degree STA and 25mm setback post.
> 
> Zero offset posts are really best suited to MTBs that have slack STAs.



In my experience many people are poorly fit on their bikes and just get used to it. Ignorance is bliss.:blush2: 

On a properly fit bike, the saddle is positioned up and back behind the bottom bracket so as to afford the rider the best position to spin round circles at the cranks. For most people, this position is somewhere near KOP. I'm not a strict KOP advocate, but I always start there when fitting someone and then encourage them to learn to feel their pedal stroke and spin circles. Once the person gets the feel for spinning circles, they may want to move the saddle slightly to suit their own particular style.

Depending on the bike's seat tube angle and the riders leg proportions, it may be necessary to use a zero setback seat post to get the proper position. Using a Thomson for fashion reasons is silly...but very common. Guess if you train yourself to ride a poorly fit bike long enough, everything becomes normal after a while.:mad2:


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## Cheers!

wim said:


> Some riders (especially those with short femurs) shove their saddle all the way forward to achieve what they believe to be a proper position over the bottom bracket. For these riders, a zero-offset seat post makes sense. With the saddle at the same position over the bottom bracket, the zero-offset post would clamp their saddle around the middle of the rails instead of at the very ends of them.
> 
> Add-on, for what it's worth: I don't think clamping a saddle at its rail ends is really a problem other than having zero adjustment options in one direction.
> 
> /w


This is what happens. 










Note:
1.) The front clamp is directly above the "STOP" mark, so I'm still within the limits
2.) THe bolts/fasteners were installed with a calibrated torque wrench
3.) I had this setup on my Kona Full Suspension Mountain Bike
4.) I did not crash
5.) I weigh 170 lbs and it is XC race courses I ride on. 

If you have a seatpost similar in design to what I have, (KCNC Ti-Pro Lite) where the rails are poorly supported, and you have the saddle biased to one end (in my case as far back as the top tube length is short on the Kona), you can bend the rails.


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## Dizzy812

Larger frame sizes have slack angles - the zero setback post often works well here.

Trust me don't clamp your saddle rails at the extremes . . .


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## BigSur

andulong said:



> By using a zero setback post on bike with a slack seat tube you can achieve the same setup as a bike with a steep seat tube and a normal setback post.


Ok, but most "comfort" or "compact" frames have a slack STA for a reason. So why put a zero offset on a frame like that? Doesn't that defeat the purpose of getting a frame with a relaxed geometry? I could see a rider with a traditional geometry race bike, add a zero offset seatpost to make the STA even more steep than it is...

I have a long femur, and I ride a Felt Z1 (slack STA). So i guess it wouldn't make sense for me to put on a zero offset seatpost. Thanks for all the responses!


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## wim

Cheers! said:


> This is what happens.
> 
> If you have a seatpost similar in design to what I have, (KCNC Ti-Pro Lite) where the rails are poorly supported, and you have the saddle biased to one end (in my case as far back as the top tube length is short on the Kona), you can bend the rails.


OK, I take it all back and state the opposite: I think clamping a saddle at its rail ends is really a problem.  

More seriously, are the top clamp arms further apart than the bottom clamp arms on the seat post in the picture? It looks that way, but I want to make sure I'm seeing this correctly. It's not saying much, but the only seat posts I've come across had the top and bottom clamp arms aligned. That may explain why I've not seen problems with forward- or backward shoved saddles. I do want to add that I've seen broken rails if the front- or rear upward bends of the rails were shoved against the rail clamps, especially if those clamps had sharp edges.


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## xxl

Wow. I thought the point of zero-offset posts was to allow more possible fitting positions on a given stock frame, kind of like different stem sizes.

I use a zero-offset Thomson, but my frame's top tube is ridiculously long, at 63.5 cm. The Thomson is very strong, stronger than the last two posts that I broke, JRA, and holds my 225 lbs. up adequately.


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## C-40

*???*



MShaw said:


> C40's obviously pretty close to 'standard.' I'm not. I've got short legs and a long torso. To get a bike that fits front to back, I've gotta ride something bigger'n my legs can handle, so I'm WAY far behind the BB unless I get something with less setback.
> 
> Compact bikes have been a doGsend for me! Get the length I need, but with standover I can live with. :nod
> 
> YMMV according to YOUR specific fit needs.
> 
> M


Frame size has nothing to do with fore/aft position, unless that larger frame also has a slack STA. Setback is strictly a function of the STA and the saddle height, regardless of frame size. Most often, one size larger frame would either have the same STA or perhaps up to 1 degree less. One degree only moves the post back a little more than 1cm.

Also, if you have the saddle height set 3cm lower than someone else of your height, that alone moves the saddle forward about 1cm.

I'm not standard at all. I've got very long legs and a short torso, with an 83cm cycling inseam for my 168cm height. Since most frames in my size have 74 or 74.5 STAs, my tall saddle height of 73-74cm helps move the saddle further back and negate some of that seat tube steepness. I use a post with 25-35mm of setback since I prefer to have my knee 1-2cm behind KOP. It also helps to use a saddle with long rails.


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## Nessism

MShaw said:


> C40's obviously pretty close to 'standard.' I'm not. I've got short legs and a long torso. To get a bike that fits front to back, I've gotta ride something bigger'n my legs can handle, so I'm WAY far behind the BB unless I get something with less setback.
> 
> Compact bikes have been a doGsend for me! Get the length I need, but with standover I can live with. :nod
> 
> YMMV according to YOUR specific fit needs.
> 
> M



Makes sense to me, other than the C40 reference.

Sloping top tube frames take standover clearance away as an issue for most people so you can just focus on top tube length and maybe, head tube length as well.

Guess I'm kind of odd but when I see someone having to resort to a funky seatpost, such as a non setback or one of those super setback jobs, it strikes me that the frame just doesn't fit the rider properly. I like to see a moderately setback seatpost sitting in the center of the saddle rails. Of course, saddle position is not based on looks or reach; it's a function of placement relative to the bottom bracket. Other things follow, not the other way around.


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## C-40

*poor post design...*

There are several brands specializing in light weight parts that are poorly designed. Here's a perfect example where the saddle rail supports have almost no bearing surface at all. The rails are likely to bend, even if the saddle was perfectly centered. Contrast this to a proper design that has at 2-3cm of contact length with the rails. With this design, you can use place the saddle all the way forward or all the way back with no fear of bending a rail. The FSA K-Force is one good design.


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## MShaw

C-40 said:


> There are several brands specializing in light weight parts that are poorly designed. Here's a perfect example where the saddle rail supports have almost no bearing surface at all. The rails are likely to bend, even if the saddle was perfectly centered. Contrast this to a proper design that has at 2-3cm of contact length with the rails. With this design, you can use place the saddle all the way forward or all the way back with no fear of bending a rail. The FSA K-Force is one good design.


Syncros, Sette (Syncros copy), Thomson, Dean, etc all have straight post seatposts with good clamps. If you read the disclaimer that came with the saddle, they usually specifically recommend AGAINST seatposts like the one in the pic above. :nod For the very reason we see in the pic.

M


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## Cheers!

wim said:


> OK, I take it all back and state the opposite: I think clamping a saddle at its rail ends is really a problem.
> 
> More seriously, are the top clamp arms further apart than the bottom clamp arms on the seat post in the picture? It looks that way, but I want to make sure I'm seeing this correctly. It's not saying much, but the only seat posts I've come across had the top and bottom clamp arms aligned. That may explain why I've not seen problems with forward- or backward shoved saddles. I do want to add that I've seen broken rails if the front- or rear upward bends of the rails were shoved against the rail clamps, especially if those clamps had sharp edges.


The bolts are meant to be parallel (evenly spaced apart from the seatpost tube). The only support the rails see are the cup shaped peice that rotates/rests against the seatpost's tube.


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## wim

Cheers! said:


> The bolts are meant to be parallel (evenly spaced apart from the seatpost tube). The only support the rails see are the cup shaped peice that rotates/rests against the seatpost's tube.


Thanks, appreciate the answer. In defense of the design I have to say that a certain type of cyclocross remount is particularly hard on saddle rails. I know this for sure . . .


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## tidi

C-40 said:


> There is no advantage to a zero setback seatpost for a road bike. Fewer people all the time take any stock in the idea that femur length and the resulting knee over pedal measurements are relevant to producing the proper rider position. It's better to have the rider properly balanced over the saddle and ignore KOP. Achieving a good weight balance nearly always requires a setback seatpost, to move the saddle back and reduce weight on the riders hands.
> 
> I found that moving my saddle back not only improves comfort, but also allows me to tolerate more saddle to handlebar drop. I've increased the drop on my bike from 9.5cm to 11.5cm with the saddle about 2cm further back. Depending on the saddle, I need a 25-35mm setback to get the position I want. Even then, the saddle will be most of the way back.
> 
> Using a zero setback post instead of the more common 20-25mm moves the clamp forward about as much as a 2 degree increase in the seat tube angle. I've used one once, but it was on a older LOOK frame with a slack 72.5 degree STA. It positioned the seat rail clamp in the same location as a newer frame with and 74.5 degree STA and 25mm setback post.
> 
> Zero offset posts are really best suited to MTBs that have slack STAs.


g'day C-40, i really enjoy reading your posts. just in regards to you mentioning your increase in saddle to bar drop, did this help you get a better sprint with the lower handlebar position? the reason i ask is that i have a good reach but i struggle to be able to transfer the power as i feel i'm not getting enough pull on the bars to execute a powerful sprint. regards


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## Peanya

C-40 said:


> Achieving a good weight balance nearly always requires a setback seatpost, to move the saddle back and reduce weight on the riders hands.
> 
> I found that moving my saddle back not only improves comfort, but also allows me to tolerate more saddle to handlebar drop.


I'll chime in here, in agreement of the above mentioned. Zero setback means you will put a LOT more weight on your hands. Not a big deal if you're sprinting all the time, or in very short races. Want real proof? That's super easy - stand up, now bend over without moving your butt back at all. You can't do it. A more rearward position allows you to bend over more while being comfortable. This also helps you reduce the drag. You might need to bring down the seat tube a tiny bit more than if it was further up though.


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