From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Bottom Bracket Threaded worng way !
Date: 12 Jun 1998 14:58:14 GMT

Sheldon Brown writes:

> This isn't really that big a deal.  While the "correct" threading
> direction is desirable, millions of bikes have been built to
> obsolete French and Italian standards, with right-hand threading on
> both sides.  These bikes do have some tendency for the bottom
> brackets to come unscrewed on the right (wrong) side, but if you
> tighten them securely enough they're OK.

Hold it.  There is a big difference.  This means the right hand
"fixed" cup will be on the left (that's OK) but the adjustable cup,
that cannot be tightened, will be on the right, the side where
precession causes the cup to unscrew.  The lock ring does not suitably
lock a right hand cup, the cup that has the odd combination of forces
that caused builders to use a left hand thread in the first place.

> My advice would be to use the existing threads, stick the bottom
> brackets in the way the threads work.  I'd suggest using symmetrical
> cartridge-type bottom brackets, tightening them enthusiastically,
> and perhaps using a thread adhesive such as blue Loctite.  This
> should provide good service.

This may avoid the unscrewing problem but won't solve the fretting
problem that these BB's tend to have.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: How much to tighten a Campy BB?
Date: 18 Jan 1999 22:59:16 GMT

Peter Prop writes:

>> velo-S"thing from the POV of keeping the right cup tight (i.e. as
>> the spindle turns, to the extent its motion has any effect on the
>> fixed cup, it would at least be a tightening motion), no? "

> No-the clockwise action of the crank BB spindle makes the bearings
> turn counterclockwise-there -by loosening the cup-I think sluggish
> BBs-like shimano-is more of a culprit than the direction of the
> threads-

It's not as simple as that.  Italian and French threaded BB's have
right hand threads on both sides.  If the left cup had the same
tendency to precess as the right cup, it would screw in and bind up
the BB, since the lock ring is trivially tight on most BB's.  It is
the peculiar sequence of chain tension and downward pressure while the
right foot is working, and upward force and chain tension when the
left foot is working that loosens the right cup.  The left cup is
immune to this action.

Jobst Brandt      <jbrandt@hpl.hp.com>