Seattube angle vs. headtube angle- Mtbr.com
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  1. #1
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    Seattube angle vs. headtube angle

    There is a lot of focus on the headtube angle and how much effect it has on a bikes riding charateristics but it is rare that the angle of the seattube is mentioned as being an important factor. I am currently riding the Yeti 5.75 which seattube angle is 71.5 and after 3 years on this very nice bike I have found myself considering buying an Ibis Mojo. The Ibis almost has the same headtube angle but the seattube angle is 73 and I am curious about how steeper angle will affect my position on the frame.

    Unfortunately I donīt have a chance to testride an Ibis Mojo and thats why I am hoping to hear from someone who has experienced different seattube angles and how it feels

  2. #2
    Nightriding rules SuperModerator
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    the steeper seattube angle helps with climbing....

    pay attention to yourself next time you climb up something steep.... first thing you do is move towards the front of the saddle.... "steepening" the effective seat angle.... this also moves more weight towards the front to keep the wheel planted...

  3. #3
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    The chainstay length is also a factor BUT don't buy another bike for a degree or so steeper seattube angle. It isn't going to miraculously make you a better climber. It can help in those rare super-steep pitches but I have little trouble with those and I'm not the best climber. Headtube angle and TT length is way more important, in my opinion. 69 degrees is my ceiling now. I think 67.5-69 is where it is, depending on travel and use.

    Here in Colorado, I used the ASR and 575 (and several other FS bikes) and climbing even the steepest stuff was not a problem (well, until my lungs gave out) so climbing is more about technique. I climb steep stuff about the same of all the bikes though the longer travel ones are a bit nice with the higher BB and a bit more capable on really rocky stuff.

    I rode the ASR, 575, X-5, El Saltamontes, and the Flux here and as my climbing technique got better, I started to climb better. Now I'm on a Turner 5.5 Spot and as I get better, I climb better.

  4. #4
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    My observation is the seat tube angle decreases and the headtube angle increases as the frame gets bigger, except for Time Trial bikes which have steeper seat angle for aerodynamics and to spin the pedals in high rpms.

    See attach pic
    Attached Images Attached Images

  5. #5
    Nightriding rules SuperModerator
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    Quote Originally Posted by older guy
    My observation is the seat tube angle decreases and the headtube angle increases as the frame gets bigger, except for Time Trial bikes which have steeper seat angle for aerodynamics and to spin the pedals in high rpms.

    See attach pic
    that might be the case for Merlin...but most other brands keep their angles (or make make very minor changes) across their sizes

  6. #6
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    Quote Originally Posted by crisillo
    that might be the case for Merlin...but most other brands keep their angles (or make make very minor changes) across their sizes

    some companies, particularly with road bikes, will steepen the HT in larger sizes in order to keep the wheelbase reasonable as TTs get longer, or slacken in smaller sizes to avoid toe overlap depending on how you look at it. It's more acceptable with road bikes because road frames often come with forks, and changing the rake can offset negative handling characteristics. A MTB frame maker really can't specify what fork rake the bike is to be used with, where a road frame can.


    ST angle: what really matters is saddle position over the BB - between the adjustment range of most saddle/post combos and straight and setback, or even set-forward posts you have huge flexibility to make the SA work, with head angle the only real way to compensate is with fork rake, and unless you get a custom made fork you are generally stuck.

  7. #7
    Nightriding rules SuperModerator
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    Quote Originally Posted by Joules
    some companies, particularly with road bikes, will steepen the HT in larger sizes in order to keep the wheelbase reasonable as TTs get longer, or slacken in smaller sizes to avoid toe overlap depending on how you look at it. It's more acceptable with road bikes because road frames often come with forks, and changing the rake can offset negative handling characteristics. A MTB frame maker really can't specify what fork rake the bike is to be used with, where a road frame can.


    ST angle: what really matters is saddle position over the BB - between the adjustment range of most saddle/post combos and straight and setback, or even set-forward posts you have huge flexibility to make the SA work, with head angle the only real way to compensate is with fork rake, and unless you get a custom made fork you are generally stuck.
    thanks Joules..you managed to say it better than me..that's what I tried to say above... forgot to add the MTB part... (I knew that was the case on road bikes)

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