The stock lug pattern: 5x114.3mm (AKA->  5x4.5 inches)
Lug bore/center bore: 60.1mm
--Significant for the use of hubcentric rings when mounting aftermarket rims (and also making sure a wheels centering hole isn't too small for a second gen xB).

Original steel wheels (steelies): 16x6.5 45mm offset
Weight: around 20-22 pounds (have heard varying reports and have not weighed one accurately)
--Weight is rim ONLY.  Tires are heavy too.

Original tire size: 205/55/16  (205mm face, 55 side ratio, fits on 16 inch rims)

Overall rolling diameter: 631.9mm
It is "best" for accuracy of the speedometer, odometer, and on-board computer readings (like MPG) to be as close to that overall diameter as possible.
The best chart for that is: http://newscionxb.com/wheels_tires/eddnogs_xb_20_wheel_tire_chart-t23.0.html
Try to stay in the greens.

What size rubber are you running?
The tires make a huge difference in altering the mph computer readings.
Use this chart: http://newscionxb.com/wheels_tires/eddnogs_xb_20_wheel_tire_chart-t23.0.html
Use the sizes in green and it should be close to the MPH in the computer.
(Whether the computer is programed slightly higher than actual, I don't know-> some vehicles are.)

The sizes closest to stock (according to that chart) are:
215/40/18 (reads -0.2575 mph off)
225/40/18 (reads 0.4991 mph off)


(Mods, please break these posts into its own thread, keeping the first post in this one cleaner and to the point-> technical info.  Edit: move this post to the new thread that asks the exact same thing.)