120mm Cartridge BB?

[74dodger]

I disassembled a very rusty and frozen BB on my Raleigh M20. The BB is obviously shot so rather than replace it with a new cage bearing BB, I'd like to go with a more reliable cartridge BB which also requires less maintenance. The spindle is a square taper, 120mm w/68mm shell.

I'm having trouble finding a replacement with a spindle this long. i'm actually surprised, I figured there would be tons to choose from.

Sheldon Brown indicates the symmetrical equivalent to a 3N 120mm BB is a 124mm which would leave the non-drive side crank arm portruding a bit extra. Funny thing is, I can't find a cartridge BB that's that long length either.

Is my only option to replace it with a cage bearing BB?

 

[Max P]

Tange all metal cartridge sq taper BBs are quite easily available in many sizes, at the longer end: 118/122/127.

 

[74dodger]

Oh, so I'd have to change length? Didn't wan to throw off my chainline since I'll be re-using the stock crankset. If so, should I go 2mm wider or shorter?

 

[FluffyChicken]

122.5 is the cartridge that Shimano replaced their 120.5 cup'n'cones with iirc.


But what chainset is it?

 

[74dodger]

Re:

7 speed Shimano cassette with a "Tracer" triple crankset.

 

[Max P]

Oh, so I'd have to change length? Didn't wan to throw off my chainline since I'll be re-using the stock crankset. If so, should I go 2mm wider or shorter?

You'll find in practise that different BB/chainset combos will give slight variations anyway due to tolerances and slight manufacturing differences. 1mm difference each side is negligible anyway and can be fine tuned with spacers.