I need to order hubcentric rings before I order my wheels.

I have a 2006 Cooper S R53. Center Bore of the wheel is 73.1.

Where can I order the rings?

 

You need to ask the wheel vendor if they will provide the ring to fit the wheel sold to you for mounting on your MINI which has a hubbore of 56.1mm

The rings come in hard plastic or metal for about $25 to $40 a set of four.

Some info on rings-
http://www.tirerack.com/wheels/tech/...jsp?techid=91&
http://www.justforwheels.com/hub-centric-rings.jsp
video

When you buy wheels from tirerack.com you get the rings to fit your car included.

There are many vendors that sell rings to fit.
http://www.justforwheels.com/index.j...sub=searchsize

Yours would be-
http://www.justforwheels.com/index.j...cat=hubcentric
$36 for a set plus shipping

Or
http://www.1010tires.com/hubrings.asp
73 mm/ 56.15 mm Plastic $24.99 or Aluminum $34.99 per set