Any terrain is a big stretch. If you're going to be doing offroad/offtrail at all, consider the fat tires. I'm currently running the fattest tires I've ever run on my xc bike. Even unencumbered you're not making any type of progress through sand or snow, even on 2.5s. You can air up the fat tires if you want to ride on trails or roads, and you can air down to almost flat especially with runflat inserts. That being said, if you're in the hills, sand, snow etc you're probably better off to just walk the bike. Even on moderate terrain with 100 pounds you're much more likely to break and wear parts, wipe out, or just exhaust yourself trying to ride up hills. I don't own a fat tire bike, I just don't find them as fun and I walk my bike when I run into deep soft sand, but they would be what I recommend for a bug out bike.