Bottom bracket compatability

richardjiles

I have the shimano fc-m311 front crankset on my commuter, I need a new bottom bracket so according to this tech doc, I need the bb-un26-k - great, but it has a plastic cup instead of metal and an amazon review told me to get the bb-un55 because it has a metal cup and is made better, but I cant find anywhere saying that these are compatible, are they? can you point me in the right direction?

http://techdocs.shimano.com/media/techd ... 667768.PDF

supersonic

Will be fine, just get the right size.

The Rookie

UN55 is better made, but nothing wrong with the plastic supporting bush at all.....works just fine and is lighter than ally!

supersonic

Plastic ones don't click or sieze as much either.