I was wondering the same thing. Couldn't find anything that says it exactly, but all the pics of the rims I've found for semi's appear to be hub centric.

 

However they are truly not either the BUDD wheel system is a true hybrid using the hub for correct center location untill the taper nut locks out any possible fore and aft movement and correctly tensions the wheel against the hub flange!
Jim & fat Monty

 

there ya go! if both ways are good enough for a semi, then 1/2 is good enough for me




btw, yes the red was sarcasm