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Old 01-12-22, 10:33 PM
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Join Date: Jun 2010
Location: Medford MA
Posts: 1,777

Bikes: Ron Cooper touring, 1959 Jack Taylor 650b ladyback touring tandem, Vitus 979, Joe Bell painted Claud Butler Dalesman, Colin Laing curved tube tandem, heavily-Dilberted 1982 Trek 6xx, René Herse tandem

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Originally Posted by dddd View Post
I did miss your posting, even as I had too-quickly scanned the thread for any mention of the reflector bracket.

Perhaps your decaleur's loading also may have contributed to your stem's clamp ear splitting? It somehow never occurred to me that the hole bore was actually tapered.
The crack was there when my dad gave it to me, which was years ago. Decaleur was added just a couple months back. I also mentioned that above, but it's ok! This thread is a wild one. I actually ground down the nut to make it fit better (no longer spreading the crack) when I was prepping it for brazing the decaleur. In the dark. In the rain. At midnight before my 6am flight.

It appears that on the Cinelli stems, the counterbore is not tapered, but the Arnold Industries nut does have a bit of a taper in this area. I think that's what caused mine.

My first experience with one of these tapered nuts was while tightening a stem, and tightening it some more, wondering why the nut didn't fully seat. I vaguely recall having then removed the nut forcefully and grinding it to a smaller size. The reflector bracket being the issue did not occur to me at that time because I had bought the stem used, without the bracket..
You are lucky to be so perceptive. I know a hundred guys who would have just blithely cranked it until they cracked it.
Owner & co-founder, Cycles René Hubris. Unfortunately attaching questionable braze-ons to perfectly good frames since about 2015. With style.
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