Thanks naks. I still have my 2008 RRS with the relatively new Cooper Zeons, so I am going to swap tires/rims.
I assume only the tire pressure monitors will have to be swapped also -- I'll do that also to make sure -- I'm assuming the 2014 RRS technology will not read the 2008 tire pressure monitors.
I just bought a set of black 20in rims off of another board member on here, and swapped out my 22's. Well, ok... I bought these to be my winter set with dedicated snow tires come winter time, however, the wife and I just wanted to see what it'd look like with the black rims on. And as with any purchase off the interweb, there was hiccups... one rim needed to be refinished (he did disclose that) that was $125 to have repaired, and then the TPM's wouldn't work, and new ones were like $270, for the 4. Needless to say, i'm into these "winter wheels" for more than I had anticipated, and oh, I still have to buy the Blizzaks come October.
All of that said, the ride from 22's to 20's is almost negligible... and I thought it'd be way "cushier" having that much more sidewall. I was wrong... these ride great. I will put the 22's back on sooner than later, but in the meantime, these came with some Pirelli's that still have great tread on them, so might as well save my brand new Continentals right?
Regarding markjeansonn's original question your speedometer is calibrated to the overall diameter of the tires regardless of the size of your wheels so as long as your 20" tires are the same diameter as those on the 21" wheels there shouldn't be any difference in your MPH reading. Discount Tire and Tire Rack have OEM upsize and downsize wheel options that result in the same diameter tire and also list a given tire's size in inches under "specs". I've also noticed there is usually a variety of OEM "take off" wheels listed on Craig's List (at least in larger cities) and Ebay though prices and added shipping make Ebay a bit less economical than what I've seen on Craig's List.
Thanks everyone. Local tire shop is scheduled to do the tire swap tomorrow, and they will be swapping the tire pressure monitors to make sure vehicles are still in sync. I'll see how both vehicles ride after that.