Originally Posted by
oneclick
Which is why the seam should be on the bottom, where the usual load will tend to force the edges together; if at the top they get pushed apart, so if there is any weakness from the seam that makes it worse. I think someone put that stay in upside down - looks as though it's not dimpled, so a less noticeable mistake.
Originally Posted by
Steelman54
Yup, its at the weld of rolled and welded type tube. Has it always been there? Almost looks like perhaps poor finish at the tube level or at Motobecane, just a guess. Either way not great.
Originally Posted by
CliffordK
If only that was on the DS, you could make a custom stainless steel chainstay protector and braze it into place and nobody would be the wiser.
I'm with @
Steelman54 that it may well have been a manufacturing defect. It almost looks like the paint curls into the seam (unless it has been repainted at some point).
The bike may well ride fine. You might look to see how the seam behaves when you put weight on the bike.
For everyone's edification, the bike is a 1982 Motobecane Jubile Sport with original factory paint. I think that the OP mentioned that he could hear creaking when he rode the bike. The crack most likely runs the length of the chain stay so a hammersmith repair wont accomplish much.
The 3 main tubes were straight gauge Vitus 888, the fork blades were too. The chain stays were "oval" meaning round-oval-round and on this model most likely made of cheap seamed tubing,
Motobecane produced many bikes during the 70's and 80's with better quality forks and main tubes but low quality seat and chain stay tubes. I have 3+ Motos made that way???
The 1982 spec sheet gives the partial details...
verktyg
