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Which bottom bracket for a 1982 Stumpjumper?

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Which bottom bracket for a 1982 Stumpjumper?

Old 06-29-20, 07:46 PM
  #1  
shanlon
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Which bottom bracket for a 1982 Stumpjumper?

Does anyone here know what the original 1982 Stumpjumper bottom bracket spindle length or model was? (Picture below)

I'm restoring one using as many original parts as I can collect, and I know that they were spec'ed with a Tange sealed unit.

The early bikes had a hodgepodge of components with a TA Cyclotouriste triple up front (ISO taper) and a Tange BB (which I assume is JIS taper). I'm not really sure how that worked.

Any help would be much appreciated.

Thanks.


Last edited by shanlon; 06-29-20 at 07:49 PM.
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Old 06-29-20, 08:00 PM
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The spindle should have a "code" stamped on it.
https://www.sheldonbrown.com/bbsize.html
Scroll down a bit for the spindle chart.
I'm wondering if that might be an "Italian" spindle, since the adjustable cup appears to have more threads exposed than normal?
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Old 06-29-20, 08:08 PM
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Thanks, but I don't have the original BB. The guy I bought the bike from had a bunch of low end parts on it, so I stripped all of those off. I'm rebuilding it properly, piece by piece.
This is why I'm looking for the specs.
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Old 06-29-20, 08:11 PM
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That's a very cool bike. If running a TA triple, why not find TA british threaded bottom bracket cups with the right spindle (the spindle will be marked 374 and the length is 123.5)? Those tend to have pretty narrow Q factors though and those stays are bowed out so maybe that will not set the crank arms far enough out to clear the frame.

Also why do you think a TA crank is ISO? Sutherlands has it as JIS; so does this site which has a good discussion,

https://www.renehersecycles.com/bott...s-demystified/

I know you want to go all original but I'd be tempted to run a shimano sealed square taper BB (or something fancier if you like). Just find a shop that is OK on returns because you may have try out different BBs until you find one that works.

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Old 06-29-20, 09:01 PM
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Thanks for your thoughts, Bikemig. I was told that the TA crankset was ISO, so this is news to me. Though this makes sense and is great to hear.

I do want to keep it entirely stock, and I think that Specialized probably spec’ed it for the frame width.
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Old 06-29-20, 09:22 PM
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Trying to "restock" a 38 year old bike is wrought with challenges of both what was "stock" and what's currently available. As example is the component in question. Crank spindle "standards" were still is a flux back then and the TA arms were not the most hard Al so the slight variations of taper and starting/ending dimensions (across the taper flats) may very well changed with wear and other standards installed. If you find the OEM specs you believe your bike was shipped with i hope they still work for the current conditions. Andy
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Old 06-30-20, 08:21 AM
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Thanks for your thoughts, Andrew R Stewart.

The crankset I bought is in excellent condition, so I hope the taper has not been affected too much. But I hear you on trying to find original parts. It’s not easy, but I have found just about everything in either excellent condition or NOS.

I’m hoping that once I identify the correct BB in the correct dimensions, I’ll actually be able to find one in decent condition.
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Old 07-23-20, 09:45 PM
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Originally Posted by bikemig
That's a very cool bike. If running a TA triple, why not find TA british threaded bottom bracket cups with the right spindle (the spindle will be marked 374 and the length is 123.5)? Those tend to have pretty narrow Q factors though and those stays are bowed out so maybe that will not set the crank arms far enough out to clear the frame.

Also why do you think a TA crank is ISO? Sutherlands has it as JIS; so does this site which has a good discussion,

https://www.renehersecycles.com/bott...s-demystified/

I know you want to go all original but I'd be tempted to run a shimano sealed square taper BB (or something fancier if you like). Just find a shop that is OK on returns because you may have try out different BBs until you find one that works.
Hey, Bikemig, I just found something on Sheldon Brown's website about TA cranks being ISO taper. Check it out. It's about halfway down the page. Thanks for your thoughts.
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Old 07-23-20, 10:17 PM
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That's a long, long time ago. Sheldon says 133.5mm:

https://www.sheldonbrown.com/bbsize.html#ta
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Old 07-23-20, 10:33 PM
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Originally Posted by Jeff Wills
That's a long, long time ago. Sheldon says 133.5mm:

https://www.sheldonbrown.com/bbsize.html#ta
Thanks, Jeff Wills. I was wondering if there would be any variation in that length based on differences in frame dimensions, but I guess that's a pretty good starting point.
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Old 07-24-20, 05:56 AM
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If you, or anyone, needs a Shimano UN55 68mm X 113mm, let me know. I have a brand new one that I bought by accident, installed, and immediately removed.
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Old 07-24-20, 07:13 AM
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Originally Posted by Papa Tom
If you, or anyone, needs a Shimano UN55 68mm X 113mm, let me know. I have a brand new one that I bought by accident, installed, and immediately removed.
Thanks! That sounds like it will be too narrow, but I’ll let you know if that ends up working.
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Old 07-24-20, 06:20 PM
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Originally Posted by shanlon
Thanks! That sounds like it will be too narrow, but I’ll let you know if that ends up working.
Sorry, I got that wrong. The BBUN55 I have is a 73mm X 122.5mm !!!
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Old 07-24-20, 10:23 PM
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Originally Posted by Papa Tom
Sorry, I got that wrong. The BBUN55 I have is a 73mm X 122.5mm !!!
Still not enough. The spindle needs to be 10mm longer. I'm pretty sure those old Stumpies didn't have 5mm of clearance between the cranks and chainstays.
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Old 07-24-20, 11:57 PM
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This is why I got three different Shimano BB-UN55's in various sizes. I need to replace the bottom bracket on my Univega Via Carisma -- it always loosens and creaks no matter what I do -- but I forgot to check the size of the original. So I got two UN55's for $8 each and one was free. Hopefully one will fit. If not, there will be other bikes...
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Old 12-09-20, 09:52 PM
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Hi Shanlon, Did you ever get this figured out? I recently picked up two identical 1982 Stumpies and I'll be restoring them over the winter. I can let you know BB Spindle spec whenever I get around to removing them.
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Old 12-18-20, 10:41 AM
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shanlon
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Yes, I figured out that it's a 137 MM Tange bottom bracket and found one that is in very good condition. Good luck on your restorations. Have you checked out the MOMBAT site? It's a great resource for restorations. 1982 Specialized Stumpjumper
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