I recently bought a used bike from a police auction that had a nasty cut in the frame (presumably caused by a angle grinder or something similar). Should I be worried about the bike's structural rigidity? If so, what should I do to mend the frame? I thought about wrapping a piece of aluminum around the damaged area and bolting it down with metal ties, but I'm not sure how much that'd help.

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  • If it is a steel frame (and it should be, given the brand name), my best bet is to weld a piece of a steel tube of a slightly bigger diameter. given that the damage does not cut through the whole thing, maybe simply welding a half-tube on top of it will suffice. In any case, repainting will be needed, and the whole frame aesthetics would be compromised if no clever design decision is made to conceal the repair. Apr 2 '18 at 18:04
  • That sounds like a good idea, but unfortunately I don't have access to any welding tools. Would JB weld or something similar work the same?
    – ks794
    Apr 2 '18 at 18:23
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    There's no such thing as "only three years". Even at a mile a day, three years is still over a thousand miles in which any pothole that you don't notice until you're on top of it could become a fatal accident. Apr 2 '18 at 19:37
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    Got it-I've decided to scrap the bike for parts and get myself a new frame. Thanks for your help
    – ks794
    Apr 2 '18 at 20:41
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    @Mazura So, you're proposing to take a dangerously broken frame, subject it to physical stress and then use it as a bike? That's a really terrible idea. Apr 3 '18 at 0:19

I personally would not ride that bike. The top tube is severely compromised now, it will get worse as cracks develop from the ends of the cuts.

No-one plans to crash so you can't resolve to always ride it 'gently', You do not want to ride over a pothole or off a curb and have the top tube buckle up into your face, neck or chest.

Your proposed fix of clamping a sheet of aluminium over the tube would not be sufficient, neither will JB weld. There is no safe solution for $30.

Unfortunately, a proper welding job will probably cost more than you paid for the bike.

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    IMHO it was unethical for the police to sell such a thing except with the express mention for 'parts use only' and maybe cut through both top and down tubes to render it unusable.
    – Carel
    Apr 2 '18 at 20:08
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    I agree, especially if it was connected with a police force that is charged with maintaining public safety. I imagine all the bikes were sold 'as-is' and 'at the buyer's risk'. Apr 2 '18 at 20:31
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    Ah well that's a bummer. Thanks for your help! (Side note: it's possible the police had "sold as is". I can't exactly remember--got too excited and didn't pay too much attention to the bike when I got it)
    – ks794
    Apr 2 '18 at 20:37
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    Sorry man. You'll just have to chalk that up as a lesson in buying used bikes - always inspect what you are considering buying very carefully. Suggest you start looking for a bike with busted wheels or drivetrain, but a good frame. Apr 2 '18 at 20:42
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    Now you are slightly less inexperienced, young padawan Apr 2 '18 at 20:46

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