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I just noticed, to my great sadness, a small-ish buckle/dent in my diagonal lower tube. (I'm riding a Cooper T200 single speed.) I just moved house; I hope I didn't do it. I probably did.

It's about half way up and looks like it's been bent against something, or crushed between something - the tube itself is still straight, it just has a bit of a ding. It's probably only dented in a fraction of an inch.

A fraction of an inch is no longer a perfect circle, though, and it'll inevitably weaken it. Question is, enough for me to worry about? Or should I just keep riding and forget it?

I ride on roads, to work, nothing strenuous, but want to be able to hit the occasional pothole or what have you without constantly thinking that my frame is going to collapse under me.

Does anyone have any actual experience with this sort of "injury"? Any suggestions how I might fix it, short of replacing the tube? I don't care if it looks a bit rough, we're through the honeymoon period, it's just a functional machine now. :-)

Thanks all.

Edit: added pictures, even though this is answered. Note that the other side of the tube to the visible dent is still perfect. (These are the same dent, from slightly different angles.)

Ding 1

Ding 2

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    While the dent there is not good, it doesn't look terribly bad. Where your dent is is probably about the lowest-stress location on the frame -- if you were going to dent it, that's the place to do it.
    – Daniel R Hicks
    Jan 28, 2015 at 12:42
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    (I once saw a bike with the down tube rusted completely in two, and still being ridden. Not that I recommend that.)
    – Daniel R Hicks
    Jan 28, 2015 at 12:45
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    John - this question is almost 2 years old. How did your bike cope with the last 2 years of riding? Did the frame crack at all?
    – Criggie ♦
    Nov 5, 2016 at 23:29
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    Hi @Criggie. Nope, she's still the same! I ride her pretty much every day and—although it took a while for me to trust that nothing bad was going to happen—I don't pay any attention to road conditions. Potholes, kerbs, whatever: she does them all.
    – John Noble
    Dec 4, 2016 at 3:41

3 Answers 3

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All steel frames of any age get a few dings from serious use.

The failure point for steel frames is usually the highest stress points: the joins. That is why we used to have fancy tubing sets likes Reynolds 351 double butted, and I notice that your frame does too.

So, if the dent is away from the joins I say the frame is ok for general use. Steel is quite a forgiving material, but I wouldn't be doing bunny hops on it :-)

If the dent is within 25% of the tube length, but more than 10cm (4 in) from a join, then I would be using it, but cautiously. If it's closer than 10cm from a join then I would get a shop to look at it.

I would add that I've ridden high-end bikes for decades after their first (heart breaking) dents. One of them has just died, but a fork failed (at the join), not the dented frame.

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    oAdditionally, One of the key benefits to a steel frame is that it can be fixed much more simply than CF or aluminium. An accomplished welder with access to tubing can easily replace a dented tube. This is a key reason for touring bikes to be made out of steel, if something goes wrong in the middle of a long journey every small village will have someone who can weld, but probably not someone with their alloy tickets (guess qualifications are less of an issue in the 3rd world, so ability and access to tools to heat treat to avoid warping)
    – DWGKNZ
    Jan 28, 2015 at 8:46
  • Great, thanks so much. Makes me feel a lot better about riding her. My dent is pretty much mid-bar so I think I'm okay. I'll keep an eye on it and make sure it doesn't get any worse. Thanks for the advice, much appreciated. (Edit: just added pictures. Let me know if your opinion has changed!)
    – John Noble
    Jan 28, 2015 at 10:37
  • Ok, that's a bit more serious: it's been squished (there is more than one dent) and abraded. I would still use it with care, but I would recommend that you get a shop or frame builder to look at it.
    – andy256
    Jan 28, 2015 at 11:30
  • Hmm. Thanks Andy. I'll find someone to have a look at it. I'm certainly keeping an eye on it as I ride for any signs that it's spreading, getting worse, etc. Appreciate the advice, thank you.
    – John Noble
    Jan 28, 2015 at 22:38
  • The damaged area will be a weak point where the tube flexes slightly as you peddle. Eventually it will start to crack. Sorry about that; it's a nice frame.
    – andy256
    Jan 28, 2015 at 23:18
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Dents in frames cause what is called a stress concentration point. Imagine you had a sheet of tinfoil, and you took a pin and poked a hole in the center of a 12x12 square. Now if you bend/warp the tinfoil many times, you'll see cracks/tears/stresses forming around that point.

The same goes for frames, however, it takes a pretty serious dent to cause accelerate fatigue to the point where it would be dangerous. As with any bike: inspect it regularly for cracks. That is something that should be done regularly anyhow. Otherwise, ride on!

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That actually can be repaired to a reasonable extent. There is a process using wooden forms that reshapes the tubes. It is not beyond the abilities of the home mechanic. As far as ridability in its current state, I wouldn't sweat it. Here's the process for rolling out a dent. If the bike is that dear to you, go for it.

Rolling Out Tube Dents

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