USAZorro

I recently dropped $20 on an old Peugeot for the Frankenbike challenge. I stripped it most of the way down and then noticed this. I can feel the crack along the entire length. I don't see myself doing much, if any "hard" riding on this, I also don't see myself paying someone to make repairs. Is this safe enough to ride gently as part of the "get mileage" part of the challenge, or no? I have no experience with failure of a stamped dropout, but evidently, in the past, riding has contributed to the stress here. At any rate, I fear the ultimate destination for this frame is wind chimes and possibly decor - just a matter of "how soon"?

Velo Mule

That crack came from the manufacturing process of the steel not even the bike. It is worth removing the paint there to see this better and get a better evaluation. Perhaps it is just a line that was created when the steel was rolled.

Catnap 

If you're certain that's a crack, then the frame is trashed and should not be ridden. A failure of the rear dropout while riding would likely cause the rear wheel to suddenly shift and come into contact with the chain stay when pedaling, especially pedaling uphill. That could lead to a crash at worst. You could probably weld the dropout back together, but I don't think it's worth the effort for a cheap old frame.

abdon 

I don't think that's a crack, steel does not have a cleavage where a crack would work so neatly. Looks more like when the metal was a sheet before getting the drops stamped out it got hit with the cutter.

I would remove the paint to see if that's has any depth, it could just be a beauty mark. If it does, find a friend with a MIG welder. That should cost you one beer. Two tops. Definitely not a six pack unless you help him with it.
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SJX426 

Is the other side flat?
Hard to tell but the view of the front showing the thickness looks like there is a line there too.
I would try to cause separation laterally and/or see if you can create a gap by spreading vertically.
Way to straight to represent a failure unless the failure was due to the features of the line.

My suspicion is that it is fine and a result of the sheet metal formation.

I would not ride it until I knew exactly what I was working with.

USAZorro

It doesn't affect the inside edge and can just barely be noticed when looking at the front edge - so I do think it's most likely a "beauty mark". Sooo back to the task of getting that fixed cup out.

repechage

Warrants review from the other side.
appears a fracture of the steel.
a splice in the coil.

weldable I would think or…

replace both dropouts

what is time and money when there are bikes to save.

ljsense

Doesn't look at all like a crack to me.

One, it's perfectly straight.
Two, the paint over it appears intact -- as in, the metal had this mark in it before the frame was painted.
Three, that straight line appears to have a ridge that changes in elevation, like rolled a rolled metal piece.
Four, a crack would show through the backside, and you've said there's nothing there.

Colorado Kid

Strip the paint and snap some shots for us. It may not be a problem.

delbiker1 

Does not look like a crack to me. It is too straight, no deviation. I think that is from the manufacturing process. As much as the bike looks like it has been ridden with that line, it seems to be there would be some separation. that is a high stress area.

iab

Defiantly not a crack. It is a witness mark in the manufacture of the sheet metal. It has not been a problem for the last 30 years, it will not be a problem for the next 30 years.

streetsurfer

I think the drop out is a stamping mark.

I think the chain stay may be cracked.

Road Fan

I'd suggest grabbing the seatstay end and chainstay end, one in each hand, and muscle them around to see if there is any motion. Do the same for the other side of the bike. If there's no motion, go build up your modern Underbike. I can't say you're golden, so I'll say you have intact genuine French gaspipe. If there is any motion on the drive side (I assume that's what we're looking at, you have toast. If the other side does the same, you really have a bad frame there, worse than toast! You could get a line of braze run down the side of the dropout, but remember the hub and the nuts/washer need to bear on that plate, so the surfaces of the dropout need to be made flat again after brazing. Can the brazing artist make sure it will be strong enough to ride after rebrazing and reshaping? I dunno. I think I'd look for another seemingly trash-looking U0-8 frame, or but essentially with all it's original integrity intact, such as it was.

tinkerbike

The drop out looks fine, probably where they clamped it down when the upper part was stamped over. But I don't like the looks of that chainstay at the right side of the photo... Is that a crack or just a scratch???

USAZorro

The photo makes it look worse than it is. It's a scratch that has a bit of surface rust.

bulgie 

Don't "strip the paint", don't "look at the other side", don't waste another second worrying about it. It is fine, just ride it.
I've probably looked at a thousand cracked bike frames over the last 50 years and repaired maybe a hundred. Never seen a crack that looked that that, though I have seen a lot of non-crack artifacts like that. And even if it broke there, you'd barely notice it, no way for it to cause a crash.

I know, easy for me to say! You're the one that has skin in the game. But I wouldn't say I was sure if I wasn't. I'm sure.

Mark B