I'm finding it difficult to get an answer for this question. 2015+ Limited and Platinum Expeditions have a rather rare option, the Continuously-Controlled Dampening suspension (CCD) that is more commonly found on the Lincoln Navigator. This option is always packaged with huge 22-inch wheels.

Unfortunately, getting good snow tires for such large rims is not very practical. Can smaller 20-inch wheels be installed on an Expedition with the CCD suspension option? I'm guessing this would also improve the ride quality.

22-inch wheels come from the factory with 285/45R22 tires while 20-inch wheels come with 275/55R20 tires, so overall diameter is pretty close. . .

 

THe biggest issue with going down in wheel size will be if the front hub and brake assembly. I would suggest going to discount tire or another shop and seeing if they will test fit the smaller rims size on your Expedition as long as nothing hits it would work. Also you should try and keep with the same diameter tire or re-calibrate your Expy to the new size tire
Just my tow cents