This is my rear hub axle.

The black nut in this photo – is it just to preload the bearings? There’s a silver threaded end cap to go on over the top of this that snugs up to it. The question is should i tighten this one up nice and tight or is it just a bearing preload (similar to a headset top cap)?

It’s a Specialized Hi-Lo rear hub off a set of Roval Fattie aluminium wheels and i can confirm that it’s probably made of cheese.

preload. hold wheel by axle ends spin it, tighten nut gently until you feel the bearings then back it off just a touch.

W
Heaven knows why they put them in hubs that don’t use angular contact bearings, there’s nowt to adjust.

It’s a cheap hub and I’ve been hammering it for two winters so it’s probably on its way out. I noticed everything was loose – cassette, end cap and this fella so I took it apart and had a look inside and the pawl design is rubbish just 3 pawls with a flimsy retaining spring to make them move! The spring had actually come unseated and only one pawl was working so I probably got to it just in time. Rubbishy Specialized wheel set with zero online maintenance!