I'm looking for wheels to put snow tires on 2012 outback,  I've located several sets of Impreza wheels (16"), which should fit based on diameter and bolt pattern.  the wheel offsets vary from 53-55, vs. 48 for outback.  Will they still work?

If they share the same bolt pattern you should have no trouble

Brakes on front may be too large to fit with 16"

outback12,

 

16 inch rims will fit your OBW. I have my snow tires mounted on the 16 inch steel rims that I used on my 2007 OBW, and kept for use on my present 2012 OBW. The 16 inchers put the speedometer out a wee bit, but with a GPS I was able to reconfigure in my head where I need to run the speedometer needle about 6 kmph faster at 50 mph or 80 kph.

 

Whichever wheels you go with, check them first on the front of your OBW, to ensure that they'll clear the rotors and calipers. If they fit on the front, they'll fit on the rear.

it isnt the wheel that will change the odometer output, but the size of the tire mounted on that wheel.

 

if you want to get as close as possible, use this tool to figure it out: http://www.miata.net/garage/tirecalc.html

 

put in your stock wheel/tire size on the left, and the new wheel/tire size you are considering on the right to see how far off your speedometer will be.