yet another wheel question

[rckstr111]

I've had a 2006 4.4L X5 for about 2 months. Pure bliss. I promptly bought a set of staggered 20" wheels to replace the 18's. I had the 20's powder-coated Anthracite and they look amazing. Here's the thing. The tires on the front have very minimal wear, mostly on the outer edge. (they came with the wheels I bought from a former X5 owner) I bought 2 new tires for the rear. Same brand, same tread, only wider. I have tire noise as I would expect with any new set of tires, but it almost feels like there's a bit of dragging in the front trans-axle. I can feel it (or something) in the steering wheel, and I would expect to some change especially because of the weight difference. However, today as I was entering the highway, the 4x4 light in the cluster came on very briefly, so I hit the tire monitor button and it went away and hasn't come on since. So here's the quandry, am I paranoid? The tire noise should clean up as the tires wear. But is there something else I should have done other than a tire mount and balance? I literally pulled the old wheels off and put the new ones on. I then pressed the tire monitor button and started driving. I'm no auto tech, but changing wheels shouldn't have me wondering if I'm gonna screw up my new ride. Maybe you X5 veterans with the big brains can help a newbie like me. Thanks in advance.