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Thread: Main Tube Angle

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    Main Tube Angle

    Why do more and more bicycles now have the main tube at an angle?
    How does it affect bike handling if any?
    I really prefer the clean and honest look of the horizontal main tube, which is so hard to find nowadays.

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    Randomhead
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    it's called the "top tube". I think slanted top tubes make sense, you get more stand-over height and people think they have bad backs so they want their handlebars to be higher. Plenty of bikes have horizontal top tubes, you might have to spend a little more. You aren't going to find many horizontal top tubes on aluminum or carbon frames though. They do exist, however. Spooky and Colnago come to mind.
    Last edited by unterhausen; 12-12-12 at 11:49 AM.

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    coprolite fietsbob's Avatar
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    I tend to think the Down-tube is More "Main".. but sloping top tubes appeal to the younger customers,
    coming off BMX and MTBs, that also have sloping top tubes.. its the familular-ity, thing..

    Cyclocross Race bikes will have a more horizontal top tube
    because they have to be shouldered and run, bike on the shoulder,
    up steep hills in races, occasionally..

    they are not hard to find if you go to bike shops and ask..

    How does it affect bike handling if any?
    not any more than any other double-diamond frame at the same price point.
    Last edited by fietsbob; 12-12-12 at 11:22 AM.

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    Quote Originally Posted by ak08820 View Post
    Why do more and more bicycles now have the main tube at an angle?
    I think bike manufacturers also want to keep their costs down by having less sizes of each model of frame.
    "Few sizes fit many" kind of thing.

    Keeping stock of different sizes is expensive, as are the molds for building carbon frames.

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    There is also the crucial saving of a few grams of material that can give a more flattering frame weight. The shorter seattube is also stiffer. Of course a longer and heavier seatpost then has to be used to span the resulting gap.

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    Randomhead
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    Over the years I became accustomed to seeing horizontal top tubes, but really, what's so special about a top tube zero degree slant that makes it superior to any other slant? Although it doesn't take much before the seat tube/seat stay juncture starts to be a structural issue

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    I recall being told outright by the good folks at Giant when they introduced the "compact" frame design it was simply a matter of dollars and sense. As mentioned above, the compact frame design allows a manufacturer to cover 2 frame sizes with a single frame. There is nothing inherently better about the compact frame vs. traditional frame with horizontal top tube. Just reduces many costs for the manufacturer.

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    Randomhead
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    that was the story when it started, but almost all companies have just as many sizes now as they did when all bikes had horizontal top tubes. If they drop any sizes, it's small frames and large frames which have a much smaller market

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    Yes, at that time they had 4 frame sizes for the compact design. Now they have 6 sizes which is maybe only 1 or 2 shy of a full size run in a traditional frame. Interestingly, from out of the compact design the "comfort" road bike has risen. If it weren't for that smallish frame the extended top tube might not have gained in popularity and the "comfort" or "endurance" road bike not be with us. Quite possible if one looks back into history this has been done before, as history typically repeats itself!

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    Andrew R Stewart Andrew R Stewart's Avatar
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    I let the fit/sizing of the bike drive whether the TT is sloped or not. The first sloping TT bike I built was in 1979. As I have built far more small bikes then large ones many of my bikes are sloping. I do find that the junction angles are harder to work lugs for but that's why we have brass. Andy.

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