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Recently picked up a steel frame and realised there was a crack on one side of the rear triangle, right by the seatpost. Crack seem to be contained towards the outer part of the tube so does not seem to affect wielded joint. Since it's a steel frame, I feel like it's good to go but a buddy thinks otherwise. Anyone experience something similar? Is it safe or am I doomed for a tragic death ☠? Any help appreciated!

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    I would say not a problem. That seam likely wasn't welded in the first place, just painted over.
    – Daniel R Hicks
    Aug 2, 2019 at 13:55
  • @DanielRHicks that's a brazed frame
    – Argenti Apparatus
    Aug 2, 2019 at 14:39
  • @ArgentiApparatus - True. It's a lugged frame that would have been brazed. But that seam in the stay likely was never brazed, just painted.
    – Daniel R Hicks
    Aug 2, 2019 at 23:44
  • I concur with the answers but from bitter experience can attest to the fact that this will only get worse, it's very likely more corrosion that will slowly eat away at the area than a 'crack' per se. You've got time, but if you'd like to retain your paint job, it's best to get this attended to sooner rather than later. I'm staring at a frame in the corner of the room now unridable with a corroded/'cracked' bottom head lug, rode it for about 1.5 years after I first noticed pretty much what you're seeing on yours.
    – Lamar Latrell
    Aug 3, 2019 at 1:24

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I think the key question is: how much strength is the elliptical plate brazed over the top of the seat stay adding to the strength of the joint? I'd guess it is adding some strength, as without it there is not much material between the main seat stay tube and the brazed joint. I'd be worried about a crack forming just below the joint which could lead to the stay detaching from the main triangle

However, if one stay detaches it likely won't be a catastrophic failure, because the other stay will still be supporting the rear triangle.

Really you need to consider the risk yourself. If you are a heavy rider who rides the bike hard there's more risk, obviously. At the very least I'd periodically inspect that area to check for any other cracks forming.

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    I’d also recommend drilling a tiny hole at the end of the crack to stop propagation.
    – Andrew
    Aug 2, 2019 at 17:17
  • Agreed, at 70kg I'm by no means heavy so I don't see this being too big of a problem. That said, this would be interesting to see through so I'll be keeping an eye on it for a while and if anything changes I'll report in for science. Thanks guys!
    – D Lucky
    Aug 2, 2019 at 18:17
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    A good framebuilder could easily repair that, possibly without much damage to the paintjob.
    – Carel
    Aug 2, 2019 at 18:35
  • It's not an "elliptical plate", it's part of the stay, sliced, then smashed down.
    – Daniel R Hicks
    Aug 2, 2019 at 23:45
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My guess is that when the frame was made the solder didn't flow into that gap completely and it's been this way since it was new covered over by paint.

If it gets worse over time it can be repaired.
If you don't feel comfortable with it you can get it repaired now.

Argenti is right, a worst case scenario is the seat stay detaching when you need it most.
Even if that happens you have other tubes to hold things together so the rear wheel won't fly off - you'll have time to slow down and get off the bike, so you might have to walk a long ways.

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The crack doesn't seem too bad, but imaging a situation when you descend on high speed and the road is turning, the bike is jolting because the road is a bit rough. So, at this moment the seatstay detaches and it may feel like your tire suddenly went flat and you may feel a loss of stability. If you are an experienced rider you might be able to take such a situation under control quickly if not crash might be inevitable.

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