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Bent Chainstay Under Brake Bridge

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Bent Chainstay Under Brake Bridge

Old 04-26-24, 03:01 PM
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Bent Chainstay Under Brake Bridge

I received this frame-set (from France), about 4 years ago, in a box with no packing. The drive-side seat-stay was collapsed at a single point, under the brake bridge, all the way to the left, so that the dropouts were nearly touching. I got a flat piece of wood in between them and opened them up enough so that I could support the frame from under-neath (with wood) and I got my foot onto the inside of the drive-side seat-stay and bounced on it. This brought it back some, and I began to think the frame had a chance. I then brought it to my co-op, where they did a little better, and got my dropouts back to 120mm and parallel with each-other. Never-the-less, there is still a tiny bit of bend at the crease on the side of the seat-stay. The bike rides great. There is no functional problem, but is this location tenable? I have heard of frame-straightening tools, and I could probably find someone in Boston, but figured an experienced opinion on this repair would not hurt. I am not as concerned with the 1/4" crease that is 2 1/8" from the brake bridge as I am the straightness of the stay. Would this be easy to correct?

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Last edited by 1989Pre; 04-28-24 at 11:36 AM.
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Old 04-26-24, 04:22 PM
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did you say "chain stay" but mean "seat stay?"
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Old 04-26-24, 04:55 PM
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Do we know the tubing brand/version? Steel tubes are pretty good with being bent a bit as long as: the cross sections remain large (no crimping/folds), the number of back and forth bending was few, the base material is of less that highest strength (or brittleness), initial construction was done well, and stuff like this. The greater the wall thickness is as a ratio to the diameter the less the possibility of the beer canning or folds and creases when bent and stays (either seat or chain) tend to not push that 50:1 ratio, not even close. And one reason why riding "comprised" steel frames that still track straight is far less a risk than what Aluminum frames are; steel cracks/fails at a fairly slow pace so routine examinations are usually suggested while the frame is continued to be used. lastly the consequence of a fully cracked stay is lessened by that other one. It is the fork's steerer/crown where potential "loss of control" is greatest Andy
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Old 04-26-24, 07:32 PM
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It is the seat stay not the chain stay lol...just ride it as it is...likely the cost to repair it isn't worth it...steel is very forgiving and it is not 'creased' so I'd ride it and not give it another thought...
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Old 04-28-24, 11:37 AM
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Originally Posted by unterhausen
did you say "chain stay" but mean "seat stay?"
Yes, sorry about that. I corrected it.
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Old 04-28-24, 11:49 AM
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Originally Posted by Andrew R Stewart
Do we know the tubing brand/version? Andy
Thanks. That makes a lot of sense. The maintubes are Vitus 172, but I have heard that on this model of Manufrance, the stays and fork are Durifort.
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Old 04-28-24, 11:58 AM
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The pictures aren't quite good enough to be absolutely sure, but I would ride that. Although I would do an alignment check. String test good enough, I think.
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Old 04-28-24, 12:20 PM
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Originally Posted by 1989Pre
Thanks. That makes a lot of sense. The maintubes are Vitus 172, but I have heard that on this model of Manufrance, the stays and fork are Durifort.
So the stays are Durifort. IIRC it's a typical 4130 type of steel and generally of medium strength/hardness. Much like Reynolds 531. So to the Vitus tubes. Given my earlier considerations and these tubes' not being super strong stuff (753, Prestige, OX Plat...) I'd follow Eric's advise too.

Coincidentally my next painting project is a Vitus 171 frame I built a couple years ago. The tubes "worked" pretty much the same as 531, SL/SP and the like. Not too hard for raking or filing. Andy
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