For a fairly conservative wheel + tire setup (all around 19x8.5 inch, +45mm offset, 255/40/19 rubber), to do a "test fit" on an otherwise stock 2006 RL (not lowered or anything), do I really only need to be concerned with the front brake caliper clearance? So I could just jack the car up, pop off one of the front OEM wheels, and bolt up the new wheel to make sure it clears the caliper enough to spin/roll?

Or do I have to worry about suspension clearance, fender liner clearance when cranking the steering wheel, etc with the car actually sitting on and/or rolling on the new wheel&tire setup?

I ask because I can only get a return guarantee on the wheels I am looking at if the wheel and tire have not been driven on and show no damage from the test fit process.

 

Your biggest hurdle is caliper clearance with that setup. Like I said in your other thread, you actually come out on top by a little in terms of the inside clearance to the suspension components. Just jack up the front, pull off the OEM wheel and put the new assembly up on the hub to double check caliper clearance before you start putting on lug nuts. If all is kosher with the brake clearance install the single assembly and lower the car. Have somebody sit in the car and turn the wheel side to side and get your hands in there to check the overall clearance inside the wheel well.

Again, I really think that with a modest setup like that your only concern is the caliper clearance. My setup is 10mm further pushed out and I don't have any rubbing issues. You should be just fine.