Taper Bearing Axial Float
Hi, to add my bit:
Taper Bearing sets need axial float so that as the bearing warms in service, it does not fail due to the high thermally induced loads.
This is normally achieved by tightening the nut until the bearing is fully seated and there is just some discernable bearing drag, then backing off by the manufacturer's specified amount (may be one or two notches on the castle nut). Read the Knott-Avonride maintenance instructions, downloadable from the web as an example.
You may find that there is a barely discernable amount of free play when rocking the wheel at 12 Oclock / 6 O clock. That's good.
The nut itself should not be tight, there is no place for a torque wrench when setting a taper bearing set.
Here are the generic instructions from the SKF website.
Single adjusting nut
While rotating the wheel, tighten the adjusting nut until there is a slight
bind and all bearing surfaces are in contact. Then back off the adjusting
nut 1/6 to 1/4 turn to the nearest locking hole, until the wheel rotates freely
with .001˝ to .010˝ end play, or clearance. Lock the nut at this position