Planning a winter road trip with the wife this year during the Christmas holiday. Headed from Illinois through Colorado and beyond to the Grand Canyon then swinging up to spend a couple of days in Jackson, Wyoming before heading back home. I'll be driving a 2010 Ford Explorer 4x4 that just got new tires put on it. Wondering if I would really need to have a set of chains for all the mountain driving we'll be doing. Can't use them here, and just want to know if I need to spend the money for one trip or not. I'll have the usual stuff like a shovel, tow strap, jumper cables, etc. Thoughts?