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Colnago Mexico Super: sheared chainstay repair or replace?

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Colnago Mexico Super: sheared chainstay repair or replace?

Old 06-15-20, 01:03 AM
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al_x
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Colnago Mexico Super: sheared chainstay repair or replace?

I would appreciate some expertise advice whether i should look to have the sheared driveside chainstay of my Colnago Mexico Super repaired or replaced and recommendations for framebuilders who could help. thx
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Old 06-15-20, 06:09 AM
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It's really hard to say without pictures. You can put them in your gallery. "Shear" isn't particularly descriptive. Is it cracked all the way around? Is there chain damage?

Sometimes it's possible to TIG weld a crack. Not sure it's a great idea, I would always replace the stay.
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Old 06-19-20, 01:57 PM
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Thanks for your input. Will upload photos when permitted (need to reach 10 posts) You'll understand what I mean by shear when you see it.
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Old 06-22-20, 09:00 PM
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Vancouver frame repair

Originally Posted by al_x View Post
I would appreciate some expertise advice whether i should look to have the sheared driveside chainstay of my Colnago Mexico Super repaired or replaced and recommendations for framebuilders who could help. thx
Paul Brodie and Chris Dekerf are two experienced and excellent frame builders in the Vancouver area. I've had several repairs done by these two fellows.
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Old 07-09-20, 04:05 PM
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Vcr frame repair

Originally Posted by Duke7777 View Post
Paul Brodie and Chris Dekerf are two experienced and excellent frame builders in the Vancouver area. I've had several repairs done by these two fellows.
V

thanks for the recommendation. i checked in with Dekerf about it, his price seemed quite high from which i inferred he wasn't terribly keen however, would do it if i in$i$ted. haven't check in with Paul yet. Toxik Harald also recommended Ross Alan who's taken over at MacTalla; he is supposedly very experienced with lugged frame building and repairs however is inundated with the shop presently and hasn't setup a workshop for all his framebuilding tools.
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Old 07-09-20, 05:03 PM
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Colnago chainstay repair

Originally Posted by unterhausen View Post
It's really hard to say without pictures. You can put them in your gallery. "Shear" isn't particularly descriptive. Is it cracked all the way around? Is there chain damage?

Sometimes it's possible to TIG weld a crack. Not sure it's a great idea, I would always replace the stay.
i know shear to mean exactly that: shear as in break off, break in half hence the eng. term shear strength.

anyway, since pictures are worth a thousand words, even a whole dictionnary full of them...sigh, Kermit's broken "frog" leg:


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Old 07-09-20, 05:13 PM
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Originally Posted by al_x View Post
V

thanks for the recommendation. i checked in with Dekerf about it, his price seemed quite high from which i inferred he wasn't terribly keen however, would do it if i in$i$ted. haven't check in with Paul yet. Toxik Harald also recommended Ross Alan who's taken over at MacTalla; he is supposedly very experienced with lugged frame building and repairs however is inundated with the shop presently and hasn't setup a workshop for all his framebuilding tools.
I almost mentioned Ross as well, but I heard he was pretty busy with the store. I've seen a couple of his Bonavia frames and they look excellent. I've talked to him a couple of times about doing frame repairs, but we didn't line anything up. He seems like a good guy.
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Old 07-09-20, 05:35 PM
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What scenario causes these failures?
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Old 07-09-20, 06:48 PM
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Well, that's sheared in the colloquial sense, but it's the result of a fatigue crack from the bending loads. Clearance dimples have led to many fatigue cracks in chain stays. Chrome probably didn't help much either.

I would say there is no point in any repair other than complete replacement. Could be welded though.
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Old 07-09-20, 06:53 PM
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Do I see chain suck evidence? The other aspect is the gap between the broken faces. The RH stay is now pulled back WRT the drop outs. If this was a result of an after failure force then OK. But if this is from the stay failing then there's some stress in that frame that was seeking release. Andy
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Old 07-09-20, 07:13 PM
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As I understand it, the early Colnago Mexico frames (with round main tubes) did not have dimpling on the chain stays. The Colnago Super frames had the chain stay dimpling.

So, if your frame has round main tubes, then it probably IS NOT a Mexico.

That could well drop the value of the frame in half, and would impact the decision of repairing vs selling as-is.

Pictures of the full frame, and lug cutouts would help confirm the ID of the frame.

Is there any deep rust on the frame?
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Old 07-15-20, 12:49 PM
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@CliffordK brings up an interesting point. I don't have a Mexico but I do have a Superissimo about 1983 vintage. It does NOT have dimples in the CS. I don't have a very good picture of the DS CS but it is the same as the NDS. The CS is ovalized. You can see it partly in this pic.
P1000501, on Flickr

Which is not anywhere near the same level of deformation of the OPS.
Here is a NDS pic.
P1000521, on Flickr

Makes me wonder if someone dimpled the CS to accommodate a poor chain line due to the wrong spindle or using a triple, again with the wrong spindle.
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Old 07-15-20, 03:11 PM
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Originally Posted by SJX426 View Post
Makes me wonder if someone dimpled the CS to accommodate a poor chain line due to the wrong spindle or using a triple, again with the wrong spindle.
No, the OP's bike has bike factory dimples in the stays. It's nearly inconceivable that was done after the stays were brazed into the frame. Your stays are round oval round, which is done by the tubing manufacturer.

I don't think I could get ROR columbus stays back in the '70s and early '80s. In any event, I have dimpled many round columbus stays, really hard to get a crank or tire to work otherwise. Might not be easy for the uninitiate to tell that the OP's stays are not ROR, but they are totally different.
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Old 07-22-20, 01:19 PM
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Generally takes more heat to remove a brazed tube than it did to put it together ...
chainstay dimples get done at the tube mill ..





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