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BB adapter size
#1
Hi everyone I am new to the site! :-)
I have a 2005 fuji captiva that I am replacing a cup and bearing BB with a cartridge style.
I have a BBun55 and a new crank set. Now I need an adapter to make it fit. The internal diameter for the tube on the frame is 50mm. Can anyone recommend an adapter for it?
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#2
(03-29-2012, 04:49 PM)bike4life Wrote:  Hi everyone I am new to the site! :-)
I have a 2005 fuji captiva that I am replacing a cup and bearing BB with a cartrage style.
I have a BBun55 and a new crank set. Now I need an adapter to make it fit. The internal diameter for the tube on the frame is 50mm. Can anyone recommend an adapter for it?

Not sure an adapter is made to do this. UN55 is most likely a 68MM bottom bracket. No way to put that into a 50MM opening. Length also needs to be considered. Are you giving us the measurement of the bottom bracket opening or of the downtube?
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#3
(03-29-2012, 07:57 PM)RBurrelli Wrote:  
(03-29-2012, 04:49 PM)bike4life Wrote:  Hi everyone I am new to the site! :-)
I have a 2005 fuji captiva that I am replacing a cup and bearing BB with a cartrage style.
I have a BBun55 and a new crank set. Now I need an adapter to make it fit. The internal diameter for the tube on the frame is 50mm. Can anyone recommend an adapter for it?

Not sure an adapter is made to do this. UN55 is most likely a 68MM bottom bracket. No way to put that into a 50MM opening. Length also needs to be considered. Are you giving us the measurement of the bottom bracket opening or of the downtube?
Yeah, it is 68mm wide I had a wc165 crank on it. I measured it and it seemed that the 107mm wide bearing was the right size. The the measuring the inside cercomfrance I got 50mm. Should I have measured from the outside?
Thanks for the help!
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#4
Let me review this so I understand correctly.

The current bottom bracket opening is 68MM. With a length "around" 107MM. But are you then saying that the inside diameter of the BB shell is 50MM?

The UN55 should have been provided with threaded adapters on each end. It should fit through the opening you have with these removed. The video on this site would give you a good idea of how to install.
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#5
(03-30-2012, 04:52 PM)RBurrelli Wrote:  Let me review this so I understand correctly.

The current bottom bracket opening is 68MM. With a length "around" 107MM. But are you then saying that the inside diameter of the BB shell is 50MM?

The UN55 should have been provided with threaded adapters on each end. It should fit through the opening you have with these removed. The video on this site would give you a good idea of how to install.

It did not come with adapters. I can feed the whole bearing set through the BB tube without touching the bike. The diameter of the bearing pack is a little over 34mm.
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#6
This bike was made for a "1 piece crank" or "ashtabula crank" that uses a different kind of bottom bracket. To use this BB, you would need to get an adapter and a new crank.

You need something like this: http://harriscyclery.net/itemdetails.cfm?ID=1335
or like this (complete with the BB): http://www.amazon.com/Pyramid-Piece-Bottom-Bracket-Conversion/dp/B000AO9O12
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#7
(04-01-2012, 10:24 PM)DaveM Wrote:  This bike was made for a "1 piece crank" or "ashtabula crank" that uses a different kind of bottom bracket. To use this BB, you would need to get an adapter and a new crank.

You need something like this: http://harriscyclery.net/itemdetails.cfm?ID=1335
or like this (complete with the BB): http://www.amazon.com/Pyramid-Piece-Bottom-Bracket-Conversion/dp/B000AO9O12

So in order to use the shimano un55 I need an american to ero adapter. Man all those different parts standards can really get confusing. Man you are a life saver !
I am ordering the part now.
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#8
"Parts Standards"? What parts standards?? Laugh or Cry. I dunno.
Wheelies don't pop themselves. (from a QBP fortune cookie)
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#9
Actually at least bottom brackets were more or less standard-ish (in the past two decades), most bikes had BSA BBs. Now today is a different situation: BB-30 and whatnot makes everything quite a bit confusing (to me). In the days of 10 speeds there were also things like Italian, Swiss and French BBs, some with bigger diameter shells, some with threads that were right hand only, some metric threads, some not. Oh, and the low-end stuff was the one-piece cranks.

On the current situation read the article by Dan Empfield
http://www.slowtwitch.com/Tech/Bottom_Bracket_Standards_2573.html
In fact those are standards, too! Just that they are different does not mean it is not standardised (also the Swiss, Italian, French, British BBs were standardised, there were just four competing standards). What is a major mess is axles: there, neither diameter nor thread count are standard, as are the bearing sizes (cups and cones), so it is (almost) impossible to replace the bent axle of a wheel.
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#10
(04-03-2012, 06:31 AM)Joe_W Wrote:  Actually at least bottom brackets were more or less standard-ish (in the past two decades), most bikes had BSA BBs. Now today is a different situation: BB-30 and whatnot makes everything quite a bit confusing (to me). In the days of 10 speeds there were also things like Italian, Swiss and French BBs, some with bigger diameter shells, some with threads that were right hand only, some metric threads, some not. Oh, and the low-end stuff was the one-piece cranks.

On the current situation read the article by Dan Empfield
http://www.slowtwitch.com/Tech/Bottom_Bracket_Standards_2573.html
In fact those are standards, too! Just that they are different does not mean it is not standardized (also the Swiss, Italian, French, British BBs were standardized, there were just four competing standards). What is a major mess is axles: there, neither diameter nor thread count are standard, as are the bearing sizes (cups and cones), so it is (almost) impossible to replace the bent axle of a wheel.

I tried to build a bike out of German and Japanese parts from the 70's. It was not a good idea. Some of those old bikes are cool though. But I don't think I will mess with them anymore.
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