BMC timemachine TMR01 - seat tube at 82 degrees

Discussion in 'Bike buying advice' started by jeff3069, Nov 22, 2012.

  1. jeff3069

    jeff3069 New Member

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    Hi,

    I wonder what's behind this supper steep ROADbike's seat-tube

    When taken all the way back (21 mm) it'll still be ~ 80 degrees

    and in no way it can go to around 73 degrees..

    Anybody ?

    Thanks.
    J


    [​IMG]
     
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  2. oldbobcat

    oldbobcat Well-Known Member

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    It's not a road bike, it's a time-trial/traithalon bike with a traditional handlebar. So the more pertinent question is, why did they spec this bike with a traditional handlebar?

    I don't know. Maybe that's why they call it a TMR01 instead of TM01.
     
  3. jeff3069

    jeff3069 New Member

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    Thanks, though the R in TMR01 stands for Road and they put it under the category of Road.. not TT


    Plus, just looked at Felt AR1 (Road alright), they tell in the site that the CT angle is ~73 while if one checks it seems like 80 degrees too
    here: http://www.saddleback.co.uk/Felt_AR1_2013
     
  4. oldbobcat

    oldbobcat Well-Known Member

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    Right, the Felt AR1 is a road bike. Generally, seat and head tube angles of road bikes are in the 72-75 degree range. Time trial bikes increase the seat tube angle 5-10 degrees, generally retain the head angle, but increase the fork offset to compensate for the forward weight shift.

    Thinking of that BMC TMR01, they probably intended that bike for triathletes who would prefer to use a road bar with clip-on aero extenders.
     
  5. jeff3069

    jeff3069 New Member

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  6. alienator

    alienator Well-Known Member

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    Ok. First, grad, as in grad protractor, is short for "gradian" which is a measure of angle that's different than degrees. 1 gradian equals 1/400 of a turn or 0.9°. Second I think your measurement of degrees is in error. I just popped that photo into Photoshop and found the angle to be about 75°, which sounds about right. There is likely a tiny bit of error in that since the contrast between the background and the seat tube is poor, and the picture is not of the highest resolution.
     
  7. jeff3069

    jeff3069 New Member

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    Thanks, the problem was the grad. only :)
    It was measured from the line between 2 wheels centers
     
  8. alfeng

    alfeng Well-Known Member

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    FWIW. I measure the seat tube angle of the pictured frame as being 74º ...

    [​IMG]


    The vertical line represents the angle of the seat tube & the other line was drawn between the wheel axles -- allowing for possible imprecision in the original photograph and/or the lines which 'I' drew, I measure the angle as nonetheless being 74º.
     
  9. tonyzackery

    tonyzackery Well-Known Member

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    Agree 100% with this article on seat tube angle with steeper being better for me as well. Smaller femur to lower leg length ratio? Try a steeper seat angle and unlock some power.

    I'd definitely use the TMR as a road bike. Good looking rig...

    http://www.bikesplit.com/bsa13.htm
     
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