1996 BB-UN51 meets 2017 BB-UN55

The bottom bracket on the 1996 Trek 970SHX finally showed some bearing play.  I decided to get a new one while I still could, none of Shimano's current MTB lineup uses square taper bottom brackets anymore, even the cheapest groups use octolink now.  As usual, manufacturing of the cheapest stuff is outsourced to outside of Japan.

1996 BB-UN51:

• made in Japan
• 30mm cartridge diameter on non-drive end
• says patent pending
• steel non-drive side threaded piece (I keep wanting to call this an "adjustable cup" because before cartridge BB's the piece would be the adjustable bearing cup for loose ball bearings, and the drive-side threaded piece would be the "fixed cup") 
• drive-side threaded piece is pressed onto BB body, in less light it's clearly a different kind of steel.  The BB body looks like it might actually be stainless.
• bearing seals say "Japan, HIC, DUA"
• the instructions that came with a UN71 I bought in the 90s listed the 50-70Nm tightening torque
• solid spindle

2017 BB-UN55:

• made in Indonesia
• 31mm cartridge diameter on non-drive end
• center of BB cartridge is machined down to save weight
• aluminum non-drive threaded piece, which now has a lip that could prevent full tightening if your frame's BB shell is a little wider than spec
• drive-side threads might be cut directly onto BB body, which does not look like stainless
• it comes with useless instructions that say have the part installed by a qualified mechanic, your pants cuff may become dirty near the chain, and refer to si.shimano.com for service instructions but all they have for the UN55 is the exploded diagram.
• a few product descriptions say the spindle's hollow but I think I remember confirming it isn't

Damn chainsuck.  True Temper OXIII triple butted steel tubing.  After 1997, asian aluminum frames got so cheap that mass produced high end steel frames disappeared.  Last of the V8 interceptors.  I suppose chainsuck is no longer a problem with the dumb new single-ring drivetrains that now need stupid huge 50 tooth rear cogs.

When I rescued the 1997 GT and 1999 Diamondback from someone's trash last year, one chain was save-able.  The other was not.  Both bikes had vines growing through the back spokes.

I had to sand off the rust to ID the beyond hope chain as an IG31.  The side plates were cracking at the rivets, probably from interference fit stress winning over rust weakened steel.

There are so many thorns in the area that I started running sealant after I got 5 punctures in one day and got tired of patching.  The GT's last owner's solution was ridiculously heavy inner tubes and a Mr. Tuffy puncture liner.  I don't know where he found these tubes, they might be as thick and heavy as one of my road bike tires.  Pictured above is one of the tubes with all of the air pressed out, next to one of the ultralight tubes I used to run in the 970SHX, when it used to weigh 23 lbs.  Even with a steel frame and rack and fat rhyno-lite rims, the 970SHX still weighs less than the GT and Diamondback, both of which have aluminum frames.