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  1. #1
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    Set tube angle and post setback.... who rides what?

    Been a little on the slow side around here lately... so I thought I'd post up an open question.

    Do you ride a no setback or setback post (if setback, how much) and what is the seat tube angle of your bike?

    I find that I prefer a 0 setback post on my MTB and CX bikes that have 73* STA. I've tried setback posts in the past, but I find that I climb a lot better with the straight post.


    My wife also uses no setback posts on her MTB.

    I've seen a lot of stock bikes coming with setback models, even though most people I know use no setback posts.

    Prime example would be the Scott Scale. Traditional 73* STA, but comes speced with setback posts (25mm setback Ritcheys).

    Aside: I was thinking about getting one in the future, but I'm in between sizes for them. I'm tall, (6' 1.5") but have short legs and a long torso. The XL has a top tube length that is close to what I prefer at 620mm. But the set tube is really long on that one. Oh the curse of being weird proportioned!
    Last edited by briscoelab; 11-12-2009 at 09:40 AM.

  2. #2
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    It depends so much on leg length and proportion, crank arm length along with seat angle and HTT length and saddle size and position that you likely won't find much consensus from a survey.
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  3. #3
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    A setback post is just a tool that can help you get your saddle back further behind the BB if it's necessary in order for you to have a proper fit to your bike- just focus on finding where your saddle needs to be in relation to the BB in order to give you the best performance. If that means you need a setback post in order to not have the clamp in a odd spot on the rails, then so be it...

    I know a lot of people that try a setback post out by clamping it in the same spot on their saddle rails as a straight post then wonder why they feel awkward on their bike. Unless your fit was not so great in the first place, any time you move your saddle back, you should also move it down, because you're effectively moving it further away from the bottom bracket.

    Personally, I got a professional fit, and I've set all of my bikes up the same way according to it (Road, MTB, and CX). In order to achieve that saddle:BB relationship, my road bike uses a straight post and the CX & MTB use setback posts. However, if you measure seat heights and how far behind the BB the widest part of the saddle is on all 3, they're the same.
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  4. #4
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    Quote Originally Posted by rockyuphill
    It depends so much on leg length and proportion, crank arm length along with seat angle and HTT length and saddle size and position that you likely won't find much consensus from a survey.
    I know... I'm quite content with my setups. I've been riding this way for a long time and am not going to change anytime soon.

    But I would argue that it should have absolutely NOTHING to do with effective top tube length. You shouldn't move your saddle to adjust for reach.

    I was just curious what others were running around here. The vast majority of people I ride with are using no setback posts on their XC bikes. Obviously they are not all just setup in the middle of the rails... some are further forward or back as needed for fit and balance.

    I just find it odd that so many bike mfgs spec out setback posts (some with an inch of setback) on their 73* STA XC race bikes. I think that puts a LOT of people too far bike for aggressive climbing and pedaling.... if they don't jack the seat pretty far forward.


    As for saddle positioning between road, MT, and CX... I ride nearly identical saddle positions for MTB and CX (ie saddle to bottom bracket location in space). But I ride a bit further back on the road (not a lot though). For MTB and CX I prefer a bit forward position for climbing and all the hammering you have to do in CX. For road racing a bit further back is better (for me) for balance, handling, and getting different muscles involved.

  5. #5
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    I prefer setback.

    For me, it hugs the rails more centered, for the same reasons Andrea mentioned.

    I have a non-setback on my RB, and it's slammed all the way back, hugging the very front of the rails. Afraid that it might break the rails at some point, since it's cantilivered out there. Hasn't broken yet.

    I also had a pro fit.

    But it's strictly a function of body and bike geometry. Everyone will be different.
    Last edited by Poncharelli; 11-12-2009 at 10:34 AM.
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  6. #6
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    Keep in mind that not all bikes have a seat tube that aligns with the BB, so HTT does come into it on bikes like some 29er's as the effective HTT can change significantly with saddle height and that might require changing seatpost offset.
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  7. #7
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    Quote Originally Posted by rockyuphill
    Keep in mind that not all bikes have a seat tube that aligns with the BB, so HTT does come into it on bikes like some 29er's as the effective HTT can change significantly with saddle height and that might require changing seatpost offset.

    The tube tube measurement still doesn't effect anything. Yes the effective top tube length can change in response to saddle placement (it does on all bikes, but more so on the one you have shown). But that means you buy a size that fits you and adjust reach with stem length and handlebar height.

    Now, if the saddle height is lower on a design like you have shown you might have to get a seat post with more setback than on a traditional design, to get far enough back. But again, that has nothing to to with the top tube measurement.

    You NEVER move your saddle in an attempt to adjust reach. You only move the saddle to change fore/aft balance, or to get your knees where they belong.

  8. #8
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    I've always assumed a post with setback was the norm and what people designed most bikes around. I once did the trig and I think setback usually amounts to about a degree of STA (but don't take my word for it).

    Whatever gets your butt in the right place, use that.

  9. #9
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    1* STA change = ~1cm fore/aft position change at a typical saddle height.

  10. #10
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    Quote Originally Posted by Andrea138
    A setback post is just a tool that can help you get your saddle back further behind the BB if it's necessary in order for you to have a proper fit to your bike- just focus on finding where your saddle needs to be in relation to the BB in order to give you the best performance. If that means you need a setback post in order to not have the clamp in a odd spot on the rails, then so be it...
    In my view, this is the perfect answer. A+ grade.

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  11. #11
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    Quote Originally Posted by briscoelab
    1* STA change = ~1cm fore/aft position change at a typical saddle height.
    I was just thinking about this because my GF Supercaliber 29er has a 72* HT and SeatTube angle, raked out further to 71* each because I am running my fork at 100mm instead of the designed 80mm. I end up having a straight post with the the saddle pushed forward even on that. But, I have found that my knees like me more forward and up than back and down.

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