I have recently purchased two Shimano UN55 bottom brackets for our new tandem frame. On close inspection I have noticed that the UN55 adapter cups which slide onto the bb main body are a very sloppy fit. Space measured as 0.8mm! They certainly do not engage with grey mastic band inside the adapter.
I have an old, unused UN72 BB and the adapter cup is quite a tight fit on the body.
Both the UN55’s and the older UN72 adapter cups have a grey mastic band inside the loose adapter cup to grab the bottom bracket body when fully tightened. My old, unused UN72 is a tight fit in its’ adapter. The new UN55's are very loose in the adapter cups. The 0.8mm space on the UN55’s do not allow the adapter mastic to engage with the body at all.
Surely two adapters can’t be wrong. Am I missing something?
Comments on this problem would be appreciated.