Shimano UN 72 Bottom Bracket
10-09-14 | 03:26 AM
#1
Thread Starter
Junior Member
Joined: Jun 2009
Posts: 129
Likes: 1
From: Osaka, Japan
Shimano UN 72 Bottom Bracket
I picked up a used UN 72 Bottom Bracket with not much wear. Usually on square tapered BB that i have used the right bearing cup is pressed permanently onto the right side and cannot be removed. But, on this BB the right side cup can come off easily, and the left side doesn't budge. Is it like this on all UN72 BBs or did I buy a bad part?
Thanks in advance!
Thanks in advance!
10-09-14 | 07:34 AM
#3
Cat 6
Joined: Dec 2007
Posts: 7,524
Likes: 236
From: Mountain Brook, AL
The early series of UN-7x series BB had removeable cups on both sides. This makes them useful for using in multiple BB threadings. Phil BB cups fit these. So if you want to use it in a French threaded frame, you're good to go with Phil cups.
Edit: The -72 was the last with removeable cups on both sides.
Edit: The -72 was the last with removeable cups on both sides.
Last edited by Ex Pres; 10-09-14 at 07:40 AM.
10-09-14 | 08:07 AM
#5
feros ferio
Joined: Jul 2000
Posts: 22,417
Likes: 1,882
From: www.ci.encinitas.ca.us
Bikes: 1959 Capo Modell Campagnolo; 1960 Capo Sieger (2); 1962 Carlton Franco Suisse; 1970 Peugeot UO-8; 1982 Bianchi Campione d'Italia; 1988 Schwinn Project KOM-10;
I think mine worked the same way. Follow the advice of others in this tread, and you should be fine.
__________________
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069
10-09-14 | 03:13 PM
#6
Ride, Wrench, Swap, Race
Joined: Jan 2010
Posts: 9,835
Likes: 1,816
From: Northern California
Bikes: Cheltenham-Pedersen racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
Sounds like the OP's bb assembly simply pulled apart on the wrong end when it was removed.
I would set the vice jaws to the major diameter of the body of the UN72, with the stuck left-side cup resting on top of the vice jaws.
I would then blast the threaded left-side cup threads with a propane torch for 15 seconds, then tap the end of the spindle so the bb body moves down through the jaws with the cup left sitting on top of the vice jaws.
Hopefully this gets the cup free of the body with only minimal force applied to the end of the spindle.
I would set the vice jaws to the major diameter of the body of the UN72, with the stuck left-side cup resting on top of the vice jaws.
I would then blast the threaded left-side cup threads with a propane torch for 15 seconds, then tap the end of the spindle so the bb body moves down through the jaws with the cup left sitting on top of the vice jaws.
Hopefully this gets the cup free of the body with only minimal force applied to the end of the spindle.
10-09-14 | 04:32 PM
#7
Senior Member
Joined: Dec 2013
Posts: 404
Likes: 2
From: Carlstadt, NJ
The early series of UN-7x series BB had removeable cups on both sides. This makes them useful for using in multiple BB threadings. Phil BB cups fit these. So if you want to use it in a French threaded frame, you're good to go with Phil cups.
Edit: The -72 was the last with removeable cups on both sides.
Edit: The -72 was the last with removeable cups on both sides.
10-09-14 | 05:54 PM
#8
Senior Member
Joined: Jan 2008
Posts: 2,421
Likes: 22
From: Aurora, IL
Bikes: '73 Raleigh RRA, 1986 Trek 500 commuter
I was doing an overhaul on a friends mountain/cross/hybrid type bike and ran across a Shimano something or other that had a plastic adjustable cup on the drive side, with an aluminum fixed cup on the non-drive side. Since the BB wasn't bad, and I couldn't get the drive side crank arm off, I chose not to further deal with it until the BB goes bad. The one in this appears to be an LP20 or something similar. I'll replace it with a UN-55 when that occurs. And go cro-magnon on the crank since a nice forum member sent me a replacement 
10-09-14 | 07:10 PM
#9
Senior Member
Joined: Aug 2008
Posts: 4,134
Likes: 192
From: Somerville, MA and Catskill Mtns
The early series of UN-7x series BB had removeable cups on both sides. This makes them useful for using in multiple BB threadings. Phil BB cups fit these. So if you want to use it in a French threaded frame, you're good to go with Phil cups.
Edit: The -72 was the last with removeable cups on both sides.
Edit: The -72 was the last with removeable cups on both sides.
The UN72 is a pretty high quality unit, and all three of the ones I have spin like buttah.
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