Sorry if someone else has already shared, but as anyone that has ever changed the rear tire on an 800XC knows, the bead is something terrible to get knocked down without a tire machine. Major fear of having to do it along the road and I would consider myself very proficient and changing tires. I had one of those chisel shaped bead poppers in my bag but had tried using it at home for tire changes and it really didn't help much. The bead area is really wide on that rear rim.
I saw the Motion Pro Bead Pro reviewed in a magazine and got one immediately.
It's pricey, I think it was around $75 at my local dealer but it works. It takes about one trip around the bead to get it pushed down a little, but then as you start your second pass, it'll knock it all the way down. The other lever in the pictures is the third one I carry with me. I've had it forever since it works on lots of bikes. Also a Motion Pro item. Has a 27mm on one end. Crazy light weight and works very good as a tire lever.