Yes. The taller wheels cause the RAM to be taller. I have a friend who couldn't get his in his garage with the 20's so he traded his 20's for 17's. It will now go in his garage.
I like the height the 20's have.
I've got 17's, I have about 3inches of clearance when i go in my garage. I thought they would give the 20 inchers lower profile tires to make it the same height, but i guess you can't go too low profile on a stock truck without looking stupid.
So this means 2 identical trucks with identical gears (355), the truck with the 17 inch wheels will accelerate faster than the one with 20 inch wheels.
I just bought a 2012 Ram 1500 big horn 4 by 4 with the 20 inch tires and it clears fine on my door and the outside asplalt is actually higher than the garage. (had a 12 by 20 carport on the back of my house and enclosed it and it works fine.) It is very close on the length though--about 5 inches in back and front. I back it in to my "stop" 2 by 4s I nailed into the asphalt. I did have a 2010 4 by 4 Ram with the 17 inch tires and I can tell the difference. The antenna wiggles more as it hits the garage door as I enter. I might suggest if you that are close or can't make it to check to see if your garage door opener is set to raise the door as high as it will go. I had a new garage door opener installed about 6 months ago and made sure it was as high as would go--the professional did it for me. If you get them out of "whack" and don't know what you are doing you will be buying a new motor as I did. LOL