1/4" leaves only 1/8" of usable tread (according to most mfg'ers). I'd buy before if for no other reason than for peace of mind. If you don't, you're gonna be worrying about it constantly taking away from the enjoyment of the trip.
I've had excellent luck with Rugged Trails on my Tundra and wouldn't hesitate to purchase again. Yes, a set of chains would be a necessity up there in the winter.
When we went on long trips with the truck/trailer, I always had two spares for the truck and two spares for the trailer. That alone guaranteed me to never have a flat! :B
Ron
