[CR] Bottom Bracket Cups & Threads - Why do they stay tight or loosen?

(Example: Framebuilders:Bernard Carré)

Date: Thu, 17 Sep 2009 11:45:53 -0700
From: "r cielec" <teaat4p@yahoo.com>
To: Classic Rendezvous <classicrendezvous@bikelist.org>
Subject: [CR] Bottom Bracket Cups & Threads - Why do they stay tight or loosen?


Ahoy ! The recent discussion of Swiss threads has prompted me to expose another empty space in my head where knowledge should have been filed many years ago.

Bottom bracket cups and threads: Any mechanical engineers out there who can explain why the cups remain tightened or why they loosen ( I mean with proper installation not because of error, cross-threading, neglect) ? Re: Threads are opposed RH and LH ?  Does it matter which side is RH or LH ? Can LH on right with RH on left still keep the bb cups tight? Would a LH-LH loosen up? Why Italian RH-RH and only one lock ring?

Thanks

Richard Cielec Chicago, Illinois; U.S.A.

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