So I'v had this little 13" 2006 Trek 4900 sitting around my garage for a few years and I felt like putting it back together. The only issue is I somehow misplaced my bottom bracket.

I believe it was a 73x110 E-Type Square taper (as the bike can only use an E-Type front derailleur).

I can't find one of these for sale...

Can I use a regular old cheap bottom bracket such as the Shimano UN53? Obviously it'll fit the frame, but will I run into any issue with chain line? I'm worried about having the chainrings too far from the BB shell.

Trek 4900

Shimano UN53

Based on what I've read, there are special square taper bottom brackets that offer the correct chainline when used with E-type deraillers. I can't seem to find any for sale either though. It may be simpler in the end to buy an integrated spindle, external bearing crankset, all of which as far as I know can accommodate an E-type derailler (you simply don't install one spacer).

Here's an option for under $100 inlcuding BB: https://www.universalcycles.com/shopp...5&category=380

Ugh not what I wanted to hear. I guess il have to search my garage some more.

This has me really curious. Unfortunately, my curiosity has not paid off with any more of a lead than this: https://www.bikeforums.net/showthread...ottom-Brackets

Seems to be an active member and maybe he still has some. Worth a shot. I may buy one too just to have since they are apparently quite rare these days!