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.

https://cimg7.ibsrv.net/gimg/bikefor...d9222cb930.png

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?

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.

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.

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.

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

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.

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.

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.

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.

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.

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...

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.

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