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  1. #1
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    Seat back or froward - I didnt think about the seat tube angle being so slack...

    Hi All

    The yelli screamy has a seat tube angle of only 70.5 degrees. I just set my seat up about the same as on my stumpjumper 29er FSR - mostlly pushed back a bit ang this gives me a good knee behind pedal - a little more glutes and hamstrings - and less quads and knees!

    honestly it all feels fine, but im not a fit expert.

    Any thoughts about moving the seat forward a bit to compensate for the slack seat angle?

    thanks!

  2. #2
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    70.5 is supper slack, are you sure that's right?

    If you had the forethought to pull measurements off your old bike try your best to mimic them on the Yelli. If not you'll have to start from scratch some what. Try to get your knee somewhere in the range of over the pedal spindle to 1cm behind. There are a few seat posts out their that you could run offset forward if you need that kind of adjustment.

  3. #3
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    Quote Originally Posted by surftime View Post
    Hi All

    The yelli screamy has a seat tube angle of only 70.5 degrees. I just set my seat up about the same as on my stumpjumper 29er FSR - mostlly pushed back a bit ang this gives me a good knee behind pedal - a little more glutes and hamstrings - and less quads and knees!

    honestly it all feels fine, but im not a fit expert.

    Any thoughts about moving the seat forward a bit to compensate for the slack seat angle?

    thanks!
    When you say you set the seat up like you had it on your SJ, are you referring to how far back on the seatpost it's positioned, or how far back it is relative to the BB?

    If you put the saddle relative to the BB, seattube angle won't make any difference other than changing where the rails are clamped. But, IF you set the saddle in the same place within the seatpost clamp, irrespective of where that is relative to the BB, then seattube angle changes everything.

    Bottom line, comparing bike fit from one bike to another bike MUST be done relative to the BB, as it's the one thing on the bike that is constant and everything on the bike is relative to the BB.

  4. #4
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    Is that a bent seat tube frame? If it is, you need to figure the effective seat tube angle...or something like that. I think that is a good name for it.
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  5. #5
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    Thanks so far guys - the effective seat tube is 73 degrees but the real is 70.5. But since the seat tube starts a little forward of the BB - the effective is higher. Still with the long seat post it will go back towards the 70.5 degree mark if that makes sense since thats the angle of the seat tube. Im just curious as to why they would make it so slack

  6. #6
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    "Im just curious as to why they would make it so slack"

    Thats how they get the short chain stays

  7. #7
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    Quote Originally Posted by surftime View Post
    Im just curious as to why they would make it so slack
    It's just one element of the overall design. One advantage of a slacker STA is that when you slam the saddle down, it moves forward at the same time, and really gets out of your way - remember that this frame is designed for rowdy riding. And in reverse, as you raise the saddle, your cockpit and ETT gets longer.

    The offset seat tube - BB junction probably comes from designing for short chainstays and tire clearance.

    YS geo chart for reference:
    Seat back or froward - I didnt think about the seat tube angle being so slack...-03-ys-large-geo.jpg

  8. #8
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    ahh - yes that makes sense

    Quote Originally Posted by dansMTB View Post
    "Im just curious as to why they would make it so slack"

    Thats how they get the short chain stays

  9. #9
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    thanks!

    Quote Originally Posted by evasive View Post
    It's just one element of the overall design. One advantage of a slacker STA is that when you slam the saddle down, it moves forward at the same time, and really gets out of your way - remember that this frame is designed for rowdy riding. And in reverse, as you raise the saddle, your cockpit and ETT gets longer.

    The offset seat tube - BB junction probably comes from designing for short chainstays and tire clearance.

    YS geo chart for reference:
    Click image for larger version. 

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  10. #10
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    Quote Originally Posted by surftime View Post
    Thanks so far guys - the effective seat tube is 73 degrees but the real is 70.5. But since the seat tube starts a little forward of the BB - the effective is higher. Still with the long seat post it will go back towards the 70.5 degree mark if that makes sense since thats the angle of the seat tube. Im just curious as to why they would make it so slack

    The effective seat angle is all that matters. What it actually is is irrelevant. What you need to worry about is how far behind the BB is the nose of your saddle. Drop a plumb bob off the nose of your saddle and get the measurement between your old bike and the Yelli the same. Like Mudge said it's all based off the BB.

  11. #11
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    ahh - ok thanks

    its very close to my stumpy FSR 29er -about 4inches each. but ill get a more exact measurement later

    Quote Originally Posted by customfab View Post
    The effective seat angle is all that matters. What it actually is is irrelevant. What you need to worry about is how far behind the BB is the nose of your saddle. Drop a plumb bob off the nose of your saddle and get the measurement between your old bike and the Yelli the same. Like Mudge said it's all based off the BB.

  12. #12
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    Quote Originally Posted by dansMTB View Post
    "Im just curious as to why they would make it so slack"

    Thats how they get the short chain stays
    How does that work?
    It's not your bottom bracket

  13. #13
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    Quote Originally Posted by BobBracket View Post
    How does that work?
    By putting the seat tube forward of the BB, it creates more room for the wheel, which is the limiter to shortening chainstays.
    You can't buy happiness. But you can buy a bike. And that's pretty close.

  14. #14
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    Quote Originally Posted by customfab View Post
    The effective seat angle is all that matters. What it actually is is irrelevant. What you need to worry about is how far behind the BB is the nose of your saddle. Drop a plumb bob off the nose of your saddle and get the measurement between your old bike and the Yelli the same. Like Mudge said it's all based off the BB.
    Both effective and actual angle matter unless the seat for the riders height is positioned at the stack height.

    And to the op, you just push the seat as far foreward og backward as you feel comfortable with.

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