"Zero offset" on adjustable seatposts?- Mtbr.com
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  1. #1
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    "Zero offset" on adjustable seatposts?

    Doing some research on adjustable seatposts and I'm confused about the term "zero-offset". I've Googled and searched the forums and from what I've read, "zero-offset" means that the mounting mechanism at the top of the post is made so that the seat is positioned a little more towards the handlebars than it would be on an "offset" seatpost. The general impression I get is that it's not a great idea and that most seat posts have some offset--just how much, I don't know.

    Online descriptions of various adjustable seatposts that I might be interested in:

    Specialized Command Post Blacklite: offset not mentioned

    KS Supernatural: zero offset (some earlier KS models, i950 seem to come in zero offset or some other unspecified offset?)

    Rockshox Reverb: zero offset

    So I'd like to know a little more about this concept in general, and in particular, how it relates to choosing an adjustable seatposts.

    If it matters, my stock seatpost is a 30.9 mm size.

    TIA.
    The secret to mountain biking is pretty simple. The slower you go the more likely it is you'll crash. ~Julie Furtado

  2. #2
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    Yes, offset is in reference to where the centerline of the saddle clamp is positioned relative to the centerline of the post. A zero offset post has the saddle clamp directly in line with the post. An offset post places the clamp further to the rear by some referenced amount.

    Whether offset is needed depends on your physical anatomy, your bike and your personal preference for bike fit. Strict protocol for bike fit may dictate a setback post, but in reality you'll usually find you need to sacrifice pedaling efficiency to keep the front end on the ground while climbing. Since dropper posts are targeted towards people doing lots of up and down riding, some manufacturers have chosen to focus on zero offset posts for now.

    I forget the model #, but I believe KS offers posts with and without setback.

  3. #3
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    Let me shorten car_nut's detailed answer: A zero-offset post has no advantages over an offset seatpost. Which one works better for you and your bike is a question of bike fit.

    Take a look at your current seatpost. If it works for you, you want to achieve the same seat position with the adjustable seatpost. Is you current seatpost zero-offset or offset? Easy to see and measure. Can you nullify the difference between your current seatpost and the new one by moving the seat for- or backwards? Measure it - or walk into your LBS and have them work on it.
    "Lorem ipsum dolor sit amet, consectetuer adipiscing elit." - And I agree.

  4. #4
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    Quote Originally Posted by car_nut View Post
    I forget the model #, but I believe KS offers posts with and without setback.
    Yes. As far as I can tell there are models with 15mm offset. There's even one with a 30 mm offset--which really seems like a lot (1.1 inches), but that's in a 27.2" mm tube diameter post.

    Quote Originally Posted by Kaba Klaus View Post
    Take a look at your current seatpost. If it works for you, you want to achieve the same seat position with the adjustable seatpost. Is you current seatpost zero-offset or offset? Easy to see and measure. Can you nullify the difference between your current seatpost and the new one by moving the seat for- or backwards? Measure it - or walk into your LBS and have them work on it.
    Looks like my current seatpost (Truvativ Hussefelt Double Clamp) has 10mm (less than 1/2") offset. Assuming that it fits me pretty well, sounds like I should aim for one of the offset models. A zero offset post would mean I'd have to slide the seat back that amount to be in same relative position that I'm in now. Using the seat I have now, that would be putting it pretty close to the limit of travel on the rails.
    The secret to mountain biking is pretty simple. The slower you go the more likely it is you'll crash. ~Julie Furtado

  5. #5
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    To (possibly) spare you and everyone else a long-winded post that may or may not apply, do you have a picture of your bike from the side?

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    Quote Originally Posted by jeffj View Post
    To (possibly) spare you and everyone else a long-winded post that may or may not apply, do you have a picture of your bike from the side?
    Will post one tomorrow.
    The secret to mountain biking is pretty simple. The slower you go the more likely it is you'll crash. ~Julie Furtado

  7. #7
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    Depending on where you have the seat clamped on the rails, you can still end up with the seat in the same position on a 0 offset as a 10mm offset post.
    OG Ripley v2

  8. #8
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    Quote Originally Posted by jeffj View Post
    To (possibly) spare you and everyone else a long-winded post that may or may not apply, do you have a picture of your bike from the side?
    Here are pix of bike and seatpost.
    Attached Thumbnails Attached Thumbnails "Zero offset" on adjustable seatposts?-full-side.jpg  

    "Zero offset" on adjustable seatposts?-post-bike.jpg  

    "Zero offset" on adjustable seatposts?-off-bike-close.jpg  

    "Zero offset" on adjustable seatposts?-off-bike-vertical.jpg  

    The secret to mountain biking is pretty simple. The slower you go the more likely it is you'll crash. ~Julie Furtado

  9. #9
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    If that is where you prefer your saddle as far as fore/aft is concerned, then I would stick with an offset clamp design so it will not put any more stress on the saddle rails than it already does. If the clamp is too far toward the front of the saddle, it becomes a bit of a lever when you're sitting with your weight on the wide part (closer to the rear) of the saddle.

    It wouldn't hurt to go with a design that has even a little more offset than the one you have to get the support where it will do the most good. The good news is that most adjustable seatposts have an offset clamp design, so you can concentrate on other features to get the one that is best for you.

  10. #10
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    Quote Originally Posted by Porschefan View Post
    Here are pix of bike and seatpost.
    More than offset, I'd wonder how much post you have out of the frame-- it doesn't look like too much to much to me in the photos, and all the adjustable posts I've seen on the market (at least my i95000) I think require at least 5 inches of exposed post require more post than I think you've got in this frame.

    Instead of a new seatpost, I might suggest simply picking up a quick release seatpost clamp from the LBS.

  11. #11
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    It looks like the post is inserted to about twice the minimum. I don't see how that is even close to being an issue

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    Quote Originally Posted by padrefan1982 View Post
    More than offset, I'd wonder how much post you have out of the frame-- it doesn't look like too much to much to me in the photos, and all the adjustable posts I've seen on the market (at least my i95000) I think require at least 5 inches of exposed post require more post than I think you've got in this frame.

    Instead of a new seatpost, I might suggest simply picking up a quick release seatpost clamp from the LBS.
    That frame has more than enough room. I have a Command post on my Felt and it has an interrupted seat tube

    OG Ripley v2

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    Quote Originally Posted by jeffj View Post
    It looks like the post is inserted to about twice the minimum. I don't see how that is even close to being an issue
    I don't think they were referring to minumum insertion, but height of the saddle at full extension with the post fully inserted. He may want to focus on a 4" travel post instead of the current crop of >5" posts.

  14. #14
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    Doh! I do think I may have misread it.

  15. #15
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    Quote Originally Posted by padrefan1982 View Post
    More than offset, I'd wonder how much post you have out of the frame-- it doesn't look like too much to much to me in the photos, and all the adjustable posts I've seen on the market (at least my i95000) I think require at least 5 inches of exposed post require more post than I think you've got in this frame.

    Instead of a new seatpost, I might suggest simply picking up a quick release seatpost clamp from the LBS.
    I think that I understand your comment. I know that the exposed portion of the seatpost in the pix is more than 5". I measured it when I first started trying to figure out dropper seatposts and it was close to, or just a bit more than 7". I'm not too sure where the top point of the measurement should be, but I think I measured to the base of the seat clamp.

    Standard drop distances for most of the posts seem to be 100-- or 125-mm (4 or 5 inches). Specialized Command Post "Blacklite" has a 75mm version also. Kind Shock has 150-mm version also. I was thinking about one of the 125mm/5" models, but it MIGHT be a close fit.

    If I'm thinking about this correctly, the amount of exposed seatpost needs to be at least the "drop distance" + the height of the collar, or whatever you want to call the part of the post that widens out and stops it from being inserted in the seat tube any further. I guess before I buy one I'd have to make sure that my top height, set up for maximum pedaling power, is equal to whatever this total is on the seatpost. I'm pretty sure that my seatpost can take the bottom portion of a 125mm seatpost, but I'd have to double check before buying.

    Let me know if I'm thinking correctly about this.

    I'm still a little confused about the offset question. I understand the concept now, but I'm wondering why some of the posts promote the "zero-offset" feature. And some, like the newest KS Supernatural and the Rockshox reverb, come with zero-offset ONLY . I think someone pointed out earlier that a zero-offset might be preferred by more aggressive riders?? Maybe for having a better position for climbing? If you're going downhill and the post is dropped, it really doesn't matter what the offset is. And if you're not riding pavement, but doing a fair amount of climbing, maybe being a little more forward would help? It's probably a fine point about bike fitment that is beyond my perception at this point.

    Assuming that my current post with a 10mm offset is set up perfectly (I don't know if it is or not), if I were to get a zero-offset post I'd have to slide it at least a half inch back, to be in same position as now, and the clamp would DEFINITELY be pretty far past the center point of the rails, which doesn't seem ideal--but maybe that doesn't matter either?

    Sorry for all the verbiage about what I'm sure is not an earth-shattering problem. Lack of experience breeds complexity....and I have time on my hands while my fractured ribs heal
    The secret to mountain biking is pretty simple. The slower you go the more likely it is you'll crash. ~Julie Furtado

  16. #16
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    Just depends on which works best for you. I advocate getting the saddle in the correct fore/aft position, while clamp toward the rear portion of the rails so the saddle is supported where it needs it the most. This will go a LONG, LONG ways toward preventing bent saddle rails.

    That said, I prefer my saddle a little more forward than many do so I generally like to use a zero offset clamp style post (like a Thomson) AND I have the saddle moved forward about as far as possible to minimize lower back pain and get me over the top of the bottom bracket. I hate the feeling that I am pushing forward on the cranks as opposed to being over the top of the cranks. Many prefer the opposite, YMMV.

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