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PostPosted: Fri Nov 16, 2012 10:37 am 

Joined: Sat Jun 19, 2004 11:08 am
Posts: 6691
Location: Urbana, Illinois
I'm curious to see if anyone know how this standard came to be? It seems like pedals the threading should be the opposite direction so that the motion would be in the tightening direction and not the direction that loosens the bottom bracket.


PostPosted: Fri Nov 16, 2012 12:09 pm 

Joined: Wed Mar 28, 2007 12:49 pm
Posts: 1590
Location: Near Horgen, Switzerland
No, if you think about the forces dragging on the cup, the pedalling forces tighten an English threaded cup. Try riding a slightly loose Italian cup you will find the RHS fixed cup comes undone in minutes. After one experience on an Italian (i.e. normal thread both sides of the frame) you would quickly develop the English standard!

PostPosted: Fri Nov 16, 2012 1:30 pm 

Joined: Mon Jan 23, 2006 6:35 am
Posts: 5072
Location: New York
I'd rather have the bigger properly torqued Italian cups! :mrgreen:

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PostPosted: Fri Nov 16, 2012 1:32 pm 

Joined: Mon Mar 26, 2012 2:45 pm
Posts: 113
Location: Bali, Indonesia

:smartass: http://en.wikipedia.org/wiki/Precession_(mechanical) :smartass:


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PostPosted: Fri Nov 16, 2012 6:40 pm 
in the industry

Joined: Thu Feb 05, 2004 3:53 am
Posts: 156
Location: Athens, GA
Left hand threads (counterclockwise to tighten) on the drive-side cups is strange as the friction from pedaling is clockwise which tends to loosen the cups..

PostPosted: Fri Nov 16, 2012 6:49 pm 

Joined: Sun May 10, 2009 3:31 pm
Posts: 445
Location: Russia, Moscow
ZeroG wrote:
friction from pedaling is clockwise which tends to loosen the cups..

It would, if we didn't have bearings inbetween cups and spindle. Luckily we do, so there is not enough friction transferred to overcome static friction between torqued BB cups threads and frame BB threads. As such the other thing we have to deal with is precession (see monkeyburger's post above) which is the reason for English thread standard.

PostPosted: Fri Nov 16, 2012 7:04 pm 

Joined: Fri Oct 28, 2011 3:25 am
Posts: 1273
Location: United Kingdom of Great Britain and Northern Ireland
monkeyburger knows his stuff.

Its a wonder the Italians have perservered with their sub-standard, standard.

PostPosted: Mon Nov 19, 2012 5:42 am 

Joined: Thu Aug 25, 2005 7:09 pm
Posts: 1235
Location: In the industry
In the past, BB cups have nothing pressing them in other than the threads.

With today's crankset designs, this issue seems less relevant.

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