I just tried installing my new rims and it seems that the wheels don't fit on the hub like the stock ones do. I've heard something about hubcentric rings that match the bore of the wheel to the car for a closer fit, could that be my problem? I've heard it's a bad idea to have the weight of the car sitting on the lugs. Thanks for taking the time to read this.

 

Hubcentric otherwise known as centering rings.
My rims came with them for my car. I tried it without em and I noticed a vibration in my steering wheel. Put em on and everythings cool.
I'm beleive it's just for that reason, to better fit the wheel on the hub.
For the 2$ it costs.. I would just get em.

.. and I have heard stories about long term problems if you don't have them.