I've got it pulled and its 121.5. Looking at VO bottom brackets, not sure whether 124 or 127 will do the trick.

I run one of these Ti BB’s. The problem is that it relies on friction fit to hold the outer shells of the bearings. Now all sealed bearing BB’s use friction to hold the bearing firm. But you can tighten down on the NDS cup to clamp down on that bearing. With these Chinese BB’s, both cups have flanges. These flanges tighten against the BB shell of the frame. In other words the cups are tightened against the frame and not the bearings. The bearings will eventually work itself loose.

Now if you could get one of these Chinese BB’s and substitute the NDS cup with a conventional flangeless cup, I imagine you’d be golden.

Does this also stand for the Shimanos on AliExpress?

My 85 has a Takagi Tourney XT. You may need a different length if you have a different crank. I'd go 124 if I was in your situation.

There are always alternatives to the UN55. I used one that was purchased from Chain Reaction (before the Shimano National embargo) until the frame snapped on the bike in which it was installed. I like the fact they have metal cups both sides but it seems many others do too. I'd try Tange or FSA in the future if need be, or a BB which allows for swappable sealed cartridge bearings. The bike I ride still has the original adjustable cups.

I just looked at the velo orange bottom brackets. Since the 121.5 worked, you could go with the 122 and purchase a 1 mm and 2 mm bottom bracket spacer for the drive side to account for any asymmetry in the original spindle. That is, unless you are looking for more ring/pedal clearance, then the 124 would be the way to go.

Love to do the bump to a great thread.

I'm in the market for a JIS symmetrical 68x113 for a nicer flip. Not a keeper ... uh, probably. A couple bb's in this size I've researched.

Promax SC-1
- 253 grams
- chromoly hollow spindle
- composite shell
- machined cups
- kinda cool looking, but black cups
- $26 on ebay

FSA Powerpro
- 256 grams?
- chromoly spindle
- aluminum cups
- $21.36 on ebay

Tange LN-3922
- 316 grams?
- steel spindle
- steel cups
- $26 on ebay

Tange LN-7922
- 113.5 length
- 235 grams
- chromoly spindle
- aluminum cups
- $70 (at least) at Soma

This is a great thread...Nice to know about the promax, SurferRosa, that's a new one for me!

Why overpay?!

ZTTO--$10.83: https://www.aliexpress.us/item/2251832711311655.html
JKLitePro--$7.37: https://www.aliexpress.us/item/3256804697674454.html
VP--$11.39: https://www.aliexpress.us/item/3256802757400584.html
Splurge on a Ti MUQZI unit for $22.94: https://www.aliexpress.us/item/2255799828403827.html

That last one- the Titanium BB, is tempting, but the design is screwy. Normally the DS cup has a flange so you can positively tighten against the frame, and the NDS has no flange, so you can tighten against the bearing. But these Chinese Ti BB's have flanges on both sides, so both sides bottom out against the frame. Now there is nothing positively clamping down on the bearings aside from friction. A dumb design.

Forgive my ignorance, but what is the failure mode you are worried about? Are the bearings loose enough in the shell that the outer surface would rotate? For the bearings to walk themselves left and right and cause wear to the inside of the BB shell? Loose enough for the bearing to shift diagonally and have the axis of rotation not aligned with axle? It seems that a snug bearing-to-axle fit would prevent the last.