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  1. #1
    Join Date
    Jul 2008
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    Chicago suburbs
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    Top Tube question

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    So I've been browsing around LBS's the past few weekends as I am seriously contemplating a new bike. As like many of you, I'm currently on a 51cm Cannondale Synapse (Carbon Fem 3 Ultegra). I'm thinking about switching over to SRAM (tested one and immediately liked the feel of it)...but the switch also involves getting a bike that fits me better, due to ongoing fit issues that I've had since day 1 with the Synapse. And yes, I've had 3 pro fittings, including 1 Retul fit and I still can't get dialed in correctly with regards to my hands (pain, numbness, tingly).

    While at a TREK dealer, the guy there told me that Cannondales are known for having very long top tubes, which is probably why I'm having issues. I went online to get the measurement of my top tube - it's 52.5cm. I then went to the Trek site to get the measurement of a 52cm Madone - it's 52.9cm! Why in the world would this guy tell me that my Cannondale has a long top tube, when in fact, the Madone has an even longer one?!? Was this guy just trying to push a Madone on me? Did he actually think I wouldn't go and check the measurements myself?

    Also stopped at a Specialized dealer the same day. My DH bought his bike from this dealer, so the owner sort of knows us. Personally, I think he is a tool (to put it nicely) and we tend to not do much business there. But I wanted to take an up-close look at a Ruby. He too, told me that my Synapse has a longer top tube, which is going to stretch me out more. Naturally, I checked the TT measurement on the 51cm Ruby, and it's 51.5...so he actually was right about the Ruby being shorter.

    I'm also a bit confused as to why some the C'dale race geometry bikes (Supersix & CAAD) both have a SHORTER TT (52cm) than the more relaxed Synapse in the same frame size? Is the longer TT common with all plush geometry bikes? Or am I missing some other key element here?

    Linda
    2012 Seven Axiom SL - Specialized Ruby SL 155

  2. #2
    Join Date
    Nov 2009
    Location
    Indianapolis, Indiana
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    10,956
    Could they be measuring them differently? Just a thought...

  3. #3
    Join Date
    Mar 2008
    Posts
    2,738
    What are their respective seat tube angles? Top tube measurements can't be directly compared unless the STA measurements are the same between the two frames.

  4. #4
    Join Date
    Jul 2008
    Location
    Chicago suburbs
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    Quote Originally Posted by Becky View Post
    What are their respective seat tube angles? Top tube measurements can't be directly compared unless the STA measurements are the same between the two frames.
    Ahhh...I did not know this. Thank you for pointing this out. I will go check those measurements out.
    2012 Seven Axiom SL - Specialized Ruby SL 155

  5. #5
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    Jul 2008
    Location
    Chicago suburbs
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    Quote Originally Posted by Catrin View Post
    Could they be measuring them differently? Just a thought...
    Well, it appears they all use the "horizontal" or effective TT length...so I would assume that they are all measuring the same way. But I suppose it's always a possibility that they aren't.
    2012 Seven Axiom SL - Specialized Ruby SL 155

  6. #6
    Join Date
    Sep 2006
    Location
    Central Indiana
    Posts
    6,132
    Eh, I've talked to any number of LBS sales people over the years to know that some of them don't know their product lines very well. A few weeks ago, someone tried to convince me that a particular company's WSD FS bikes had short top tubes/standover than their unisex counterparts. No, actually they don't but thanks for the helpful salespitch.

    Now, don't get me wrong; it's hard to commit that stuff to memory year and year. I get it to some degree, but I think they should be careful in making geometry generalizations.
    Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.

    --Mary Anne Radmacher

  7. #7
    Join Date
    Mar 2008
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    2,738
    Quote Originally Posted by indysteel View Post
    Eh, I've talked to any number of LBS sales people over the years to know that some of them don't know their product lines very well. A few weeks ago, someone tried to convince me that a particular company's WSD FS bikes had short top tubes/standover than their unisex counterparts. No, actually they don't but thanks for the helpful salespitch.
    Indy, so true! My only "WSD" bike has identical geometry to the company's unisex "comfort carbon" geometry....and a girly paint job

  8. #8
    Join Date
    Apr 2009
    Location
    Tucson, AZ
    Posts
    4,713
    Maybe they measure differently? Giant's bikes seem to have freakishly long top-tubes, so by comparison, Trek and Cannondale aren't too bad.

    I have the same question about the CAAD/SuperSix. They're on the long side, but they might actually work for me. Shorter top tube, less steep seat tube angle. What gives?
    At least I don't leave slime trails.
    http://wholecog.wordpress.com/

    2009 Giant Avail 3 |Specialized Jett 143

    2013 Charge Filter Apex| Specialized Jett 143
    1996(?) Giant Iguana 630|Specialized Riva


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  9. #9
    Join Date
    May 2008
    Location
    northern Virginia
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    5,845
    Quote Originally Posted by Becky View Post
    What are their respective seat tube angles? Top tube measurements can't be directly compared unless the STA measurements are the same between the two frames.
    Yeah, I would try to measure something else that takes into account angle differences, like seat post to stem.

    - Gray Trek Madone 4.7 road bike, mystery crack in top tube repaired by Calfee, Bontrager Affinity RXL saddle
    - Red Trek 6000 mountain bike, Bontrager Evoke WSD saddle

    Gone but not forgotten:
    - Silver Trek 2000 road bike
    - Two awesome and worn out Juliana saddles

  10. #10
    Join Date
    Apr 2009
    Location
    California
    Posts
    371
    Quote Originally Posted by nscrbug View Post
    Well, it appears they all use the "horizontal" or effective TT length...so I would assume that they are all measuring the same way. But I suppose it's always a possibility that they aren't.
    They may all be "measuring the same way", but that doesn't mean they are measuring equivalent lengths.

    Imagine a bike with a very vertical seat tube. To set up a proper saddle to crank relation, this bike would use a seat post with a large setback. Now imagine a bike with a very tilted back seat tube. This bike might have a seat post with no setback. With identical saddle to handlebar length, the second bike will have a much longer (effective) top tube.

  11. #11
    Join Date
    Sep 2007
    Location
    Uncanny Valley
    Posts
    14,645
    The weird thing is that my 50 cm '07 Synapse Feminine has a 50.5 ETT. It does have a pretty steep STA though. Unfortunately they took the archived specs down and I didn't save a copy, but I want to say mine is 75 vs. your 74. Wasn't somebody just talking about trigonometry - will 1 of difference over say 70 cm of seat tube, seatpost and saddle make a 1.5 cm difference in the reach??
    Speed comes from what you put behind you. - Judi Ketteler

  12. #12
    Join Date
    Mar 2008
    Posts
    2,738
    A little bit of reading on the subject:

    http://www.billbostoncycles.com/seat_tube_angle.htm

    http://www.velofitter.com/storage/Ro...lines.4.10.pdf (page 4)

    The rule of thumb is that, for every degree that the STA increases, the effective top tube increases 1 cm.
    Last edited by Becky; 08-18-2011 at 01:42 PM.

 

 

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