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  1. #1
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    56 cm Sloped tt vs 58 cm straight tt

    I currently ride a 56 CM Specialized Langster ('08 London because I used to think I was cool). I'm planning on selling that bike for a few reasons (mainly I want a steel frame with a non-sloping top tube that will accept fatter tires since the roads near me are horrific) and building up a new bike with Fyxation's Eastside Track Frameset. I'm a little stuck with what to do about sizing, however. My Langster seems really small; I'm about 6'1 with pretty short legs (31'' inseam) and a long torso and so it feels like I'm always way out in front over the bike when I am riding. I mainly ride around town and to and from work (about two miles on flat ground, so nothing major) so the ability to throw the bike around isn't a big deal to me. I'm much more interested in having a comfortable bike that I can ride at a relatively relaxed pace for long periods of time without feeling like I'm really cramped (I'm throwing a coaster brake and porteur bars on the new bike, so definitely not built for speed).

    I've purchased both the 55cm and 58cm versions of the Eastside Track Frameset and don't really know which one I should build up. I haven't had too many bikes, and so I'm not sure how the sloped top tube of the Langster translates when measured against the more traditional geometry of the Eastside Track. I've copied the geometry of all three bikes below; if anyone has any ideas about which might be best for me I'd really appreciate any insight.

    Specialized Langster 56 CM Geometry

    Top Tube Length (Horizontal) 565 mm
    Seat Tube (C-Top of top tube) 520 mm
    Head Tube Length 180 mm
    Heat Tube Angle 73.0 
    Seat Tube Angle 73.25    
    Bottom Bracket Drop 69 mm
    Chain Stay Length 405 mm
    Wheel Base 991 mm
    Standover Height 786 mm
    Fork Rake 43 mm

    Fyxation 58 CM Geometry

    Top Tube (effective) 580 mm
    Top Tube (actual) 580 mm
    Seat Tube (C-Top of top tube) 580 mm
    Head Tube Length 159 mm
    Heat Tube Angle 73.0 
    Seat Tube Angle 73.5    
    Bottom Bracket Drop 60 mm
    Chain Stay Length 400 mm
    Wheel Base 993 mm
    Standover Height 836 mm
    Fork Rake 38 mm
    Fork Length 380 mm
    Seat Post 27.2 mm
    Headset Style 1 1/8 Threadless
    Bottom Bracket 68mm English
    Rear Hub Spacing 120 mm
    Material 4130 Cr-mo Frame / 4130 Cr-mo Fork

    Fyxation 55 CM Geometry

    Top Tube (effective) 560 mm
    Top Tube (actual) 560 mm
    Seat Tube (C-Top of top tube) 540 mm
    Head Tube Length 130 mm
    Heat Tube Angle 73.0 
    Seat Tube Angle 73.5    
    Bottom Bracket Drop 60 mm
    Chain Stay Length 400 mm
    Wheel Base 979 mm
    Standover Height 809 mm
    Fork Rake 38 mm
    Fork Length 380 mm
    Seat Post 27.2 mm
    Headset Style 1 1/8 Threadless
    Bottom Bracket 68mm English
    Rear Hub Spacing 120 mm
    Material 4130 Cr-mo Frame / 4130 Cr-mo Fork

  2. #2
    Senior Member elcruxio's Avatar
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    Horizontal top tube and effective top tube are basically the same thing. Actual top tube in sloping frames is of no importance at all.
    So the langster horizontal or effective top tube (htt or ett) is 565mm which seems really short for your height (especially if you have short legs)
    The fyxation 55cm has a htt of 560 which is even shorter so definitely no that.
    The 58cm has a htt of 580mm which to me seems pretty good.
    There other things that affect the actual reach to the handlebar like seat tube angle and head tube angle but all the frames are so similiar in those regards that i'm not gonna go there.

    Build up the 58. You get the reach you need (15mm more than the langster). Also put a decent length stem on it (none of these 30-50mm fixie ridiculous mess up yor handling stems. 90-130mm is good)

  3. #3
    Senior Member zandoval's Avatar
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    Quote Originally Posted by elcruxio View Post
    Horizontal top tube and effective top tube are basically the same thing. Actual top tube in sloping frames is of no importance at all.
    Nice to know - See guys purchase a slanting top tube for the looks then slamming their bars down - Not really considering the slant just makes one more factor not to deal with....
    No matter where your at... There you are... Δf:=f(1/2)-f(-1/2)

  4. #4
    Senior Member elcruxio's Avatar
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    Quote Originally Posted by zandoval View Post
    Nice to know - See guys purchase a slanting top tube for the looks then slamming their bars down - Not really considering the slant just makes one more factor not to deal with....
    There are actually a few good sides to slanting top tubes, even though the measuring still happens with ett and htt.
    If the seat tube "mouth" is lower then more seat post is showing. This then means that you are sitting on a longer steel/carbon pole which then (I know you are guessing it) flexes and absorbs a bit more bumps and vibration.
    Also it would seem that the compact geometry (sloping frames) allows for a frame to fit a larger segment of the population and more different body proportions.

  5. #5
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    Make sure, when you build the bike up (58cm, yes), that you get a seatpost that has a little setback to the clamp; not all have it, and that will give you a touch more adjustment for that longer torso.

  6. #6
    coprolite fietsbob's Avatar
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    with same size wheel/tires ..

    The top of the front of the top tube to the ground similar?

    obviously the rear is lower, seat tube shorter on one..

  7. #7
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    Quote Originally Posted by DX-MAN View Post
    Make sure, when you build the bike up (58cm, yes), that you get a seatpost that has a little setback to the clamp; not all have it, and that will give you a touch more adjustment for that longer torso.
    I actually purchased the Velo Orange Grand Cru long setback seatpost so I'm really glad to hear your advice. I ended up getting a 70mm stem so sort of in the middle of what you suggest but if it's too small I will go bigger.

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