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  1. #1
    on by skijor's Avatar
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    Frame rigidity no-brainer ?

    The 2011 Surly Big Dummy has a straight sloped TT. The TT is curved on past years' models. Would this difference translate to a somewhat stiffer and better climbing bike compared to the '08-'10 models, all else being equal?

    This is related to the Dummy lost its curves thread in the Utility forum.

  2. #2
    Tell it as it is Silverbraze's Avatar
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    National team mechanic speak
    I am always amazed that people think frame tubes heat up enough to gobble up measurable amounts of watts from the pedals on their way to twisting the rear hub via the chain
    Where do you think the wattage on the pedals goes to?
    if you have a curved or straight top tube?

    Top tube shape will have no effect on how you go up a hill
    Your engine will
    Worry about that!

    If bikes were some how faster because they are stiffer, then we would make them as stiff as a granite block.
    and if you believe the market hype
    bikes would be perpetual motion by now
    it's steel
    it's lugs
    let the others get on with the madness
    www.llewellynbikes.com
    www.framebuilders.org

  3. #3
    on by skijor's Avatar
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    Ok forget I mentioned the climbing part. I'll try again, a curved TT frame will have a slightly more compliant ride quality versus one with a straight TT. Is that fair to say? Thanks for the input Silverbraze

  4. #4
    Randomhead
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    it will not have a significant effect on the climbing feel of this bike.

  5. #5
    tuz
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    Yeah I think top tubes are mostly stressed in compression, a mode in which tubes are really strong. Plus they hardly are solicited. With a heavy load at the back and climbing out of the saddle they might get stressed in bending (tail wagging the dog effect), but since the bend of the tube is coplanar to the frame... I doubt any difference will be felt.
    homebuilt commuter, mixte, road and track (+ Ryffranck road)
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  6. #6
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    [QUOTE=skijor;11418713]Ok forget I mentioned the climbing part. I'll try again, a curved TT frame will have a slightly more compliant ride quality versus one with a straight TT. Is that fair to say? {QUOTE]

    Theoretically, perhaps. But like Dazza said, don't fall for the market hype. You would never notice a difference.
    The bent tube was a nice concession to standover clearance, I'm sure it was changed to cut production costs.

  7. #7
    on by skijor's Avatar
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    Ok, thanks to all for the help. I suspected the production cost factor too. I am looking to build up a BD and don't feel strongly one way or the other regarding the TT. Just wanted to get some solid opins.

  8. #8
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    I doubt it drops the cost much, there are plenty of dime store bikes out there with really nicely bent frames. Not just pouches mid tube as one sees on a few of the big name custom frame makers. Nice progressive curves. That is virtually a no cost thing. It could be that they moved production, and the newer producer didn't want to do it. But once the tooling is all set, not sure how it would lower the price enough to mater.

  9. #9
    Framebuilder
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    Quote Originally Posted by Peterpan1 View Post
    I doubt it drops the cost much, there are plenty of dime store bikes out there with really nicely bent frames. Not just pouches mid tube as one sees on a few of the big name custom frame makers. Nice progressive curves. That is virtually a no cost thing. It could be that they moved production, and the newer producer didn't want to do it. But once the tooling is all set, not sure how it would lower the price enough to mater.
    Surly says it will lower the frame cost by $100, but like you, I doubt that extra bending step would account for all of that. It looks like the elimination of the bent tt was done to give all their mtb-type bike a more uniform appearance...and they probably negotiated a lower price point with the manufacturer in the process

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