EDIT: I realized this is much more suited for the Bike Mechanic forum. Feel free to ignore this as I can't figure out how to delete it! My apologies.

Hey all,

I'm currently doing a few upgrades / cleaning up my (new-to-me) old Trek 1400 (possibly an '89? Blue with white decals).

I decided to take the bottom bracket off so I could clean the inside up so it doesn't get jammed in the future (it took a some overnight soaking and leverage to get the drive side off) and the non-drive cup is totally thrashed (not my doing).

I'm wondering what my best route is for replacing the cup. Current BB is a UN52 68 113 (1.37 x 24 - Don't think this is necessary but more info is better I suppose).

Should I just buy a new cup (UN54 cup) like this for about $14:

Amazon.com : Shimano UN54 Left Bottom Bracket Cup (68-mm BSA) : Bottom Bike Brackets And Accessories : Sports & Outdoors

Or am I better off spending $24 for a brand new UN55 for $24:

https://www.amazon.com/Shimano-Tapere...bottom+bracket

At the moment, I'm unsure the differences between a UN52 and UN55 (55 has metal cup and better internals?) as I haven't found much info on the UN52. I'm going to do some more research, but I was hoping you guys might know the answers to my more "specific" question on whether to upgrade or go for the cup. As far as I can tell, there is no damage to the UN52 other than the cup.

Thanks,

Alex

Alex,
First, you did the right thing by removing the old BB if you expect long life out of your bike rebuild moving forward.
If the crankset and chainrings are not worn, then replace the entire BB with the UN55. Be sure to get the Shimano version and not an aftermarket BB...the last link you show is correct. Spindle length is critical for the best chainline...so get the 113mm spindle length if that is what your old BB is either marked or measures.

Many in your shoes would replace the entire crankset with Ultegra with the gearing you may prefer...such as 50/34. Modern cranksets are much better and less problematic than old square taper but many on this forum still own square taper BB bikes and like them just fine.

Good luck with your build.

FYI, an Orgin8 is about 100g lighter than the Shimano and I have countless trouble free miles with one.

Origin8 Torqlite bottom bracket black 113mm spindle, 68mm width

I'd spend the extra $10 and get the UN55. I'm not a fan of plastic cups.

Either that or check your LBS or coop for a used metal cup salvaged/saved from a retired cartridge bottom bracket.