Took apart my 1986 Mongoose ATB today and the bottom bracket spindle is totally pitted. The BB is a Tange, made in Japan. Mine is stamped S3, F-3, B, which sort of corresponds to this Sheldon page, but mine is longer - like 125mm. Having recently gone through a nightmare of trying to match up an Ofmega spindle, giving up and replacing the whole thing with a Shimano UN55, I am thinking of doing the same here.

Am I understanding it right that I need to buy a UN55 in 68x127 size to do this? This thread seems to suggest so for a different bike ...

I suppose I can also go with a replacement spindle like this, but for an extra $15 I get an all new BB ...

What do you think?