You don't have any scalloping on those tires by any chance?
Scalloping? 
That rear one looks like it is from the picture. The front one looks a little squarish, which can come from overinflation for a long time (like +3-4 PSI over nornal), but hard to tell from the pix angle.
Either one can cause this problem: most of the time I've seen it, it came from a squared-off rear tire (from long touring, straight-up riding), or bad bearings, either at the steering head or the swingarm pivot.
To test the steering head bearings: sit on the bike, both tires on the ground, pull the bars fully to one stop and hold the brake tight. Then, using your butt, shift the bike forward and back while "feeling" for a little "thump" in the front forks or handlebars that might indicate some looseness. There will be a very small amount of losseness coming from the front forks (unless they have 100,000 miles like mine, then it's a LOT), because the insides of the fork tubes wear. But, you are looking for it right by the big nuts on the upper steering crown. You might be able to touch the crown during the shifting back & forth to feel it there.
To test the swingarm bushings, have someone hold the bike vertical for you while it is on both tires, then grab the rear wheel all the way at the back at try to pull it toward and away from you, in the same direction as the axles (left and right, if you will). There might be a visible tightening and loosening of the chain with this act, if there is lots of play.
Sometimes, if the bearings and bushings are both bad, new tires won't help. It also can come from an unevenly-worn chain or worn sprockets: test for this on the centerstand. Make a pointer out of wire (coat hangers work good) and point to the bottom edge of the chain as it sits still. Then slowly rotate the rear wheel and watch the chain to see how far up & down it moves from this point. More than 1/4" will cause some input to the bike's handling, especially while decelerating, and especially when decelerating down a steep hill.
