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I just picked this frame up for $100. Is this a crack? It looks and feels deeper than a surface scratch. I intended on this being my 1st build, should I continue? I hope I didn't waste my money Frame 1 Frame 2 Bianchi

Mindcontrol
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  • Steel or Al ? It looks like a deep scratch in powder coating. A metal tube wouldn't (probably) crack that way. Il looks as if somebody was clumsy with a tool. – Carel Jul 29 '17 at 20:49
  • Thank you. Honestly I don't know if it's steel ie AI. Everything I read online about this frame is steel. Still new to the game. – Mindcontrol Jul 29 '17 at 21:19
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    The starting point is a concern - right on a small radius corner - exactly where a crack would start. I would suggest treat it as crack until proven otherwise. – mattnz Jul 29 '17 at 21:20
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    Sand it down and find out – paparazzo Jul 29 '17 at 23:08
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    If I do that I'll ruin the paint right? And then what...? Feels like I'll be in a worse situation. – Mindcontrol Jul 29 '17 at 23:10
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    You can tell steel from alu with magnets ;) – PTwr Jul 29 '17 at 23:19
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    No stick with a magnet. Therfore AI??? – Mindcontrol Jul 30 '17 at 00:34
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    You can rebuild a bike that might be crack or you can find out. Bike can be painted. – paparazzo Jul 30 '17 at 00:36
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    It looks like the material one side of the line is slightly 'higher' than the other. If you can feel the ridge this makes, it's definitely a crack. – Argenti Apparatus Jul 30 '17 at 01:41
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    Apropos of nothing: what is that a braze on for? It looks like it's for a friction shifter but the bike looks too new for downtube shifting. It'd be a weird place and too big for cable guides. – RoboKaren Jul 30 '17 at 02:35
  • Just remember if it fails suddenly then your ride comes to a very quick stop, as does the rider. The condition of the paint is utterly irrelevant if your underlying frame is flawed. Take it to a frame repairer or a bike shop for a proper opinion. I think you've been taken for a ride by the seller. – Criggie Jul 30 '17 at 09:05
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    @RoboKaren for a long time cable stops were separate parts mounted on friction shifter mounts. For example, Trek still had those in Lance Armstrong era carbon frames, and Armstrong sometimes used a friction shifter for front shifting. – ojs Jul 30 '17 at 09:40
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    It's possible that it's a deep scratch (and it's also an odd place for a stress crack). It's in a location where a scratch would be likely, from, eg, laying another bike on top of it and then dragging it off. As suggested, sand it slightly to see what's below the paint. – Daniel R Hicks Jul 30 '17 at 12:47
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    Borrow an endoscope camera, there are cheap digital ones and route it inside from the steering tube. If it's a crack you'll see it from the inside as well! – Carel Jul 30 '17 at 20:31
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    @RoboKaren - The braze-on is for a downtube shifter. – Daniel R Hicks Jul 31 '17 at 01:52
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    @carel +1 for thinking of cool new toys/tools to buy. $9 USD on dx.com plus a 2-8 week wait. – Criggie Jul 31 '17 at 01:54
  • Maybe the question is more: Would you rather bet $100 on it being a crack or bet your life on it not being one? – ImportanceOfBeingErnest Aug 05 '17 at 18:06

2 Answers2

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Yes, that is a crack, or at least looks to be with about as much certainty as a pic can provide. That's a relatively common place for cracks to occur, with the thick square-edged boss creating a stress riser on the thin tube.

That the line of it continues into the area where a shifter or cable stop would cover the paint adds to my doubt that it's a scratch in the paint.

Nathan Knutson
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The only way to know for sure (unless you have access to an X-ray machine or ultrasonic tester from your side job ... say at Boeing or Airbus) is to take the paint off and see if it's a surface scratch or deep crack.

Since it's a metal bike, sanding it down won't hurt it and if it is a crack, your bike is toast anyway. Aluminum frames can't affordably rewelded like a steel frame.

Update: If you have balls or labia of steel and are willing to risk it (WARNING: STUPID ADVICE FOLLOWS) you could mark the endpoint of the crack with a sharpie and carefully monitor its progress while riding gently. If it lengthens or widens, it's a crack. If it doesn't, it still might be a crack. In any case, it'd be highly risky.

RoboKaren
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