Tractor tires do the same thing.  Unless the tire is purely symetrical
there is always uneven wear as one section of the tread is just a teeny
bit less surface area than the other.  Once one lug is a bit worn the
tire then hops to the next one, etc.

This is cut and paste from an old article on http://www.truckinginfo.com/
Google cache has it still.

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Irregular wear patterns are caused by abrasion that is concentrated in one area of the tire tread instead of across the entire
footprint. Side forces created by turning, off tracking, incorrect toe, etc. can drag or slip the tire across the pavement and
concentrate wear on one side of the tire or one side of the ribs. Out-of-balance conditions and brake skids can make the tire bounce
or skip down the road rather than run smoothly and in contact with the road surface. Naturally, every time the tire lands in a
certain spot, it wears faster there. Tread pattern design and tire construction determine where the pressure on the footprint is
concentrated. If it is not spread fairly evenly across the tire’s footprint, irregular wear patterns will result.
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Nate, I can't figure the dynamics of it, but every time I've seen the
alternate wear (cupping) pattern the cure was a GOOD alignment and some
combination of shocks, ball joints, and/or tie rod ends.  I can see where
the ball joints or tie rod ends could give that pattern. I'll be damned if
I can see how shocks on a solid axle could do it - but experience says it
will. Frequent rotation and balance also seems to help a lot.

I worked in tire shops for years way back when and the scalloping is
usually either caused by bad shocks or a bad wheel balance allowing a
harmonic vibration to set up in the tire.  It is an inside outside
balance thing if I remember correctly.

Those MTR's also wear out really fast compared to say a BFG.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08.  Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com