1990s Specialized HardRock BB Replacement
 

Hello. I have a 1990s era specialized hard rock sport, and I noticed significant play in the BB. Upon removal and further inspection, both the cups and the axle are pitted. Although the pitting is minor and would probably not present an issue for a while, I would prefer to just replace the BB.

The BB seems to be of the 3N size as demonstrated on Sheldon Brown's Bottom Bracket Size Database. And it is being used with SAKAE SR Cranks.

The suggested symmetrical equivalent is 124mm. Unfortunately, I am having trouble finding modern BBs in this size. I see the BB UN-300, but it is a 122.5 mm. What are my options that arent extremely expensive? Any way to correct the chainline of the 122 mm option?

Thank you in advance!

you will be fine using the 122.5mm BB assembly.
the "difference" is about the same as the gap of a modern high voltage automotive spark plug... or two lawn mower spark plug gaps.

meh.

1.5mm total is .75mm per side. I think your chainline will be just fine with a 122.5 BB.

Thank you! I got it on order!

Thank you! I got it on order!

Ideally when replacing the BB one will check on the amount of clearance between the chain stay and the inner chain ring before removing the BB. If that gap was less than a few MMs I would be very careful about installing a shorter BB axle as the ring might contact the frame under pedaling loads. If the gap was fairly large then the concerns about clearance are less. The same goes with how much travel the ft der has. if the resulting chainline is different one wants the ft der to be able to be adjusted to this new range of travel and not "bottom out" on either its limit screws or against the side of the seat tube.

Generally changing the front chain line by a Mm or 2 is not a big deal WRT the chain running or with shifting as long as the system is checked and readjusted as needed. Andy

If the old one is notched-ring cups that come off with a pipe wrench hooked wrench, and the new one is a cartridge, you will also need the cartridge socket (Park bbt-22 or clone)

I ordered it too! Thank you!