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Shimano UN 72 Bottom Bracket

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Shimano UN 72 Bottom Bracket

Old 10-09-14, 03:26 AM
  #1  
Frenchosa
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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!
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Old 10-09-14, 04:49 AM
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Turn it over? just kidding.

I've not had one with a removable R cup, either, but I've seen the pressed-on cups come off before.
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Old 10-09-14, 07:34 AM
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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.

Last edited by Ex Pres; 10-09-14 at 07:40 AM.
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Old 10-09-14, 08:00 AM
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As always, install the fixed cup first until it bottoms out. Then install the BB from the left with the BBT tool. You should be ready to go.
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Old 10-09-14, 08:07 AM
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I think mine worked the same way. Follow the advice of others in this tread, and you should be fine.
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Old 10-09-14, 03:13 PM
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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.
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Old 10-09-14, 04:32 PM
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Originally Posted by Ex Pres View Post
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.
Yep, both cups are removable. I use one in my Raleigh.
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Old 10-09-14, 05:54 PM
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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
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Old 10-09-14, 07:10 PM
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Originally Posted by Ex Pres View Post
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.
Yes, and this is why I have a stash of used UN72s as well as Phil French rings. This way I always have a stock of high quality BBs that are compatible with French threaded frames.

The UN72 is a pretty high quality unit, and all three of the ones I have spin like buttah.
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