Originally Posted by
arex
Get a Shimano UN5x or UN72, rather than a UN26. The UN26 NDS cup is plastic, not metal, and you don't want that. The plastic will eventually break down. A UN51, having a lipless NDS cup, will allow for tighter adjustment than the lipped cup of a UN55.
Given about 2000 miles per year, with a heavy rider, won't the bearings need replacing before the plastic oxidizes? Or is the UN55 generally more durable?