Mercury Bottom bracket

[Philq]

Yesterday I took apart and cleaned the eccentric bottom bracket on my Mercury. It has the Thorn 130 PCD EX Bearing Single Crankset. I've had what I thought was a spare bottom bracket kicking around for some time so thought that I'd replace this at the same time but it didn't look like it was long enough so as any play in the old one was minimal after a regrease I've now put it all back together.

My question is: is this the correct bottom bracket? It's labeled as "Thorn EX bottom bracket 68/73mm" and has a part number 24783 but this brings up no results on the SJS website.

[PH]

I don't know the answer, but is the original sealed bearing? If so there's not much else to go wrong with them, just replace the bearings as and when required.

[JohnR]

My Mk 3 Mercury came with one of these https://www.sjscycles.co.uk/bottom-brackets/107-shimano-un55-73mm-shell-english-thread-sealed-cartridge-taper-bottom-bracket in 107mm length. Shimano, however, has discontinued the UN55 so Thorn/SJS has had to look for other compatible BBs such as this https://www.sjscycles.co.uk/bottom-brackets/tange-seiki-ln3922-73-mm-jis-english-square-taper-bottom-bracket-107-mm . My understanding is that the two dimensions which matter are the thread size (73mm for my bike) and the length (107mm) to give the chainline to suit the Rohloff hub. 110mm length will also be OK as the EBB shell can be moved sideways within the frame.

[PH]

My Mk 3 Mercury came with one of these https://www.sjscycles.co.uk/bottom-brackets/107-shimano-un55-73mm-shell-english-thread-sealed-cartridge-taper-bottom-bracket in 107mm length.

Philq's bike has a completely different chainset, requiring a completely different, external bearing, BB.