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  1. #1
    Senior Member
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    Is she done for?

    Just found evidence that somebody tried and failed to steal my bike, probably over this weekend while I was at work. I assume it's beyond repair, but I figured I should ask. My dad bought this Motobecane Grand Touring new in 1975, and it's been mine for several years now.

    motobusted.jpg

    I know it's not a particularly nice or valuable bike, but it has some sentimental value, which is why I'm asking if it's fixable. Pardon the bad picture, I'll take better if they're needed.
    http://www.pedalroom.com/bike/1976-motobecane-grand-touring-restomod-12850

  2. #2
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    Obviously done for.

  3. #3
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    Fair enough. Is it significantly unsafe to ride?

    It's the down tube, so in my head it seems as if the weight on the top of the bike would not compress the tube, but rather stretch it as the wheels try to splay outward against it, but I'm no physicist.
    http://www.pedalroom.com/bike/1976-motobecane-grand-touring-restomod-12850

  4. #4
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    Is it just the dent?

    If so, ignore it and ride the bike. If the tube is bent, the acid test is to see if it still rides straight, and if so, ride it.

    These bikes are made of relatively ductile grades of steel, and can handle a dent or two. It may/will eventually fail but eventually can be a very long time. I've seen steel bikes with upset (buckled) down tubes up behind the head lug (front end collision) go many, many thousands of miles with no hint of failure. Others develop stress cracks and eventually break apart, but I've never seen a steel bike fail from a simple dent in the tube.

    BTW- yes, your right. Downtubes are tension members, but the main stress is torsional, resisting the twisting (rocking) forces pedaling applies to the bottom bracket shell. They also stabilize the head tube against the twisting (side) forces that the fork introduces.
    Last edited by FBinNY; 07-16-14 at 08:06 PM.
    FB
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    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  5. #5
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    Yep, upon closer inspection it's just the dent. From the side you can't hardly see it.
    http://www.pedalroom.com/bike/1976-motobecane-grand-touring-restomod-12850

  6. #6
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    Quote Originally Posted by Hellarar View Post
    Yep, upon closer inspection it's just the dent. From the side you can't hardly see it.
    Then she ain't done for until you say she's done for.
    FB
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    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  7. #7
    Senior Member chriskmurray's Avatar
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    I will second the opinion of just ride it. Keep an eye on it for sure but I would likely forget about it in time. Even if it were to fail chances are it would not be catastrophic.

  8. #8
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    And my smashed handlebars, but that's unrelated from a nasty spill last summer. Continue riding I shall, thanks for the words of advice!
    http://www.pedalroom.com/bike/1976-motobecane-grand-touring-restomod-12850

  9. #9
    Hi-Tech Redneck Johnny Mullet's Avatar
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    Yep, ride that bike!
    Putting the fun between my legs.......
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  10. #10
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    Oh, a dent? I thought it was something else.

  11. #11
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by FBinNY View Post
    she ain't done for until you say she's done for.
    Absolutely. Steel takes a lickin' and keeps on tickin'.

  12. #12
    7-speed doomsday prepper ThermionicScott's Avatar
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    Ride it into the ground!
    Quote Originally Posted by chandltp View Post
    There's no such thing as too far.. just lack of time
    RUSA #7498

  13. #13
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    Great story. Love that's it still with the family. You should continue to enjoy it for many years.

  14. #14
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    Merely a flesh wound!

  15. #15
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    If the tube isn't pierced, just keep on riding it. As far as the brake levers, grind off the suicide lever mounts and put some cane creek hoods on.

    IMG_20140528_011056_780.jpg

  16. #16
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    I wasn't sure if it was safe to take a grinder to those, thanks for the heads up. I ride on the hoods a lot, and they do a number on your thumbs when it's real dry out.
    http://www.pedalroom.com/bike/1976-motobecane-grand-touring-restomod-12850

  17. #17
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    Ride it till the wheels fall off.

  18. #18
    Senior Member bhchdh's Avatar
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    Quote Originally Posted by 1986raleigh View Post
    Ride it till the wheels fall off.
    Then put on new wheels and ride it some more.

  19. #19
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    If you're really concerned about the appearance of the dent, you can get it pulled with one of those pins spot welded to the center, then use the special slide hammer to pull it out. Then the pin is ground off flush. It mars the paint in the center of the dent, but the dent will be mostly gone. A little appropriate color touch-up paint and you're good to go.

  20. #20
    Senior Member
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    Is that something I'd go to a metal shop for? A frame builder? I assume not just any LBS would have the tools necessary for that.
    http://www.pedalroom.com/bike/1976-motobecane-grand-touring-restomod-12850

  21. #21
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    Quote Originally Posted by Hellarar View Post
    Is that something I'd go to a metal shop for? A frame builder? I assume not just any LBS would have the tools necessary for that.
    Often the best advice is to leave bad enough alone.

    Nothing you can do will improve structural integrity. OTOH it's always possible to make things worse. The slide hammer remedy is usually best suited to thin sheet metal, such as on auto bodies or MC gas tanks. The structural tubing in frames is thicker walled and sterner stuff than that, so odds of success are more limited, and you'll still have the bulges at the corners of the dent to deal with.
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    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  22. #22
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    Steel. Is. Real.
    If you don't know the way, you shouldn't be going there.

  23. #23
    Senior Member RPK79's Avatar
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    Slap some bondo in there sand down and repaint.

  24. #24
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    Quote Originally Posted by FBinNY View Post
    Often the best advice is to leave bad enough alone.

    Nothing you can do will improve structural integrity. OTOH it's always possible to make things worse. The slide hammer remedy is usually best suited to thin sheet metal, such as on auto bodies or MC gas tanks. The structural tubing in frames is thicker walled and sterner stuff than that, so odds of success are more limited, and you'll still have the bulges at the corners of the dent to deal with.
    Right. What is it they say? "There is no problem so bad you can't make it worse." I'll just ride it as is. A friend of mine actually also suggested bondo which I think is funny, but probably not worth the effort. I'll just try and forget about it.
    http://www.pedalroom.com/bike/1976-motobecane-grand-touring-restomod-12850

  25. #25
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    Quote Originally Posted by Hellarar View Post
    I wasn't sure if it was safe to take a grinder to those, thanks for the heads up. I ride on the hoods a lot, and they do a number on your thumbs when it's real dry out.
    If you have a bike shop in town that's been around since the '70s or earlier, they might still have some non-safety-lever pivot pins that are compatible with Diacompe and Weinmann levers in their brake part bins. If they do, there's no need to take the hacksaw approach.

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