"Effective" seat tube angle for medium Enduro?- Mtbr.com
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  1. #1
    CJH
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    "Effective" seat tube angle for medium Enduro?

    I stopped by my LBS to test ride an Enduro but they did not have any in medium. Instead I came home with a catalog that I have been reading.

    At any rate, I realize with the interupted seat tube design that the 69* seat tube angle is effectively steeper. Can anybody give me an idea of how much?

    My current ride is a Jamis Dakota hardtail with a 73.5* seat tube. I have the saddle slammed all the way back to get in the position I prefer. I'm hoping the Enduro will be a bit more laid back.

    Thanks.

  2. #2
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    With the "flip-flop" linkage feature on the Enduro, the 69.5 degree side is actually the more slack angle of the two. If you want a steeper angle, simply "flip-flop" the linkage and the angle will be at 70.5 degrees. I keep mine is the 69.5 mode right now, if I ever upgrade to a 5 inch travel fork, i'll try the 70.5 degree angle out.
    Last edited by bdee; 05-04-2004 at 04:47 PM. Reason: the "degree" symbol i typed got changed to a question mark.

  3. #3

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    Quote Originally Posted by CJH
    At any rate, I realize with the interupted seat tube design that the 69* seat tube angle is effectively steeper. Can anybody give me an idea of how much?

    I'm hoping the Enduro will be a bit more laid back.

    Thanks.
    I'm afraid I'm not following you. As far as I know the seat tube angle is in fact 69º. However, if you pretend the ST is not interrupted and follow it down to where it would intersect the down tube you’ll notice that would-be-intersection is in front of the shell or bottom bracket.





    Now, that doesn’t change the ST angle. However, were the fame a traditional double triangle and have a 69º ST the seat would be much further behind the bottom bracket and much further away from the heat tube than it is on the Enduro. Is this what you’re referring to when you say it’s “effectively steeper” (because it’s closer than a traditional double triangle with the same metrics would be to the BB & HT)?

    The ST angle will change with the flip flop. In the lower BB setting the ST angle is 68º.

  4. #4
    CJH
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    Hi Low Rent,

    I'm probably not explaining something correctly. This concept used to be discussed on this forum and in the bike mags many years ago when the interupted seat tube designs first appeared on the market. I've not really followed the industry much in the past few years due to a back injury (hence my interest in the Enduro) so I don't know how, or if, it is still discussed.

    I did a search but could not find anything.

    I realize the seat tube *is* 69*, but like you said if your drew an imaginary line along the plane of the actual seat tube it would point in front of the bottom bracket.

    What I'm saying is that if your drew an imaginary line from from the seat-post clamp down to the bottom bracket, you would have the equivalent seat tube angle of a traditionaly framed bike -- this would determine the "effective" seat tube angle.

    It's actually much more complex than I'm making it out to be since the actual seat tube is not on plane with the bottom bracket. In actuality the "effective" STA will change with how high the saddle -- effectively more shallow as the post is extended.

    In other words, the 69* STA on the Enduro does not ride the same is a 69* STA on a traditional double-diamond frame. In the latter example you would be sitting much farther back on the bike assuming all else is equal.

    So yes, you seem to realize what I'm saying.

    If you look at Specialized Geometry specs you'll notice that the FSR XC has a very shallow STA - not something one would expect on an XC bike.

    The Stumpy, OTOH, now that is has a pierced seat tube, has a STA of 73* - the ST is now on plane with the BB with this design.

    I suspect the Enduro effective STA is very similar to the FSR XC, but I thought I'd check here and see if anyone had any insight.

    Obviously I'll get a better idea when I test ride.

  5. #5

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    Quote Originally Posted by CJH
    Hi Low Rent,

    I'm probably not explaining something correctly. This concept used to be discussed on this forum and in the bike mags many years ago when the interupted seat tube designs first appeared on the market. I've not really followed the industry much in the past few years due to a back injury (hence my interest in the Enduro) so I don't know how, or if, it is still discussed.

    I did a search but could not find anything.

    I realize the seat tube *is* 69*, but like you said if your drew an imaginary line along the plane of the actual seat tube it would point in front of the bottom bracket.

    What I'm saying is that if your drew an imaginary line from from the seat-post clamp down to the bottom bracket, you would have the equivalent seat tube angle of a traditionaly framed bike -- this would determine the "effective" seat tube angle.

    It's actually much more complex than I'm making it out to be since the actual seat tube is not on plane with the bottom bracket. In actuality the "effective" STA will change with how high the saddle -- effectively more shallow as the post is extended.

    In other words, the 69* STA on the Enduro does not ride the same is a 69* STA on a traditional double-diamond frame. In the latter example you would be sitting much farther back on the bike assuming all else is equal.

    So yes, you seem to realize what I'm saying.

    If you look at Specialized Geometry specs you'll notice that the FSR XC has a very shallow STA - not something one would expect on an XC bike.

    The Stumpy, OTOH, now that is has a pierced seat tube, has a STA of 73* - the ST is now on plane with the BB with this design.

    I suspect the Enduro effective STA is very similar to the FSR XC, but I thought I'd check here and see if anyone had any insight.

    Obviously I'll get a better idea when I test ride.
    You're right, there's no substitute for a test ride to find out what your seated position will be. You're obviously well aware of the options you have to change your seated position, e.g. changing stem length and/or angle, changing the seat's fore/aft postion on the post, changing post from/to set back, changing H-bars, etc.

    To answer your initial question before your test ride, the Enduro will feel much more laid back than your current ride. Even though the ST is more forward on the bike, the seat will ultimately be further behind the BB than your current ride. However, I'm going to bet that the stem will be shorter and the bars higher than your HT. As a result you'll be more upright and may not immediately notice that you're further back on the bike becuase your reach will be shorter--you'll feel and be closer to the H-bars. Within even a few feet on your test ride you'll feel all of this out and know quickly if it's what you're looking for.

    Let us know how it turns out.

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