mac,Questionable tires can be a huge factor , what are they? Say you have 'S' rated tires AND of an entry level pricepoint of a CRAPPY brand - I saw a video of such poor tire performance ,slow mo , and the wobbling and deformation whilst rotating highway speed was shocking water balloon-like.There was in 60's TV show "The Prisoner" , had a fictitious "Monster" security force of "controlled weather balloons" and SH!%TTY tires look & act just like the ROVERS in the show - all bellowing DISCOMBOBULATING. Now your crappy tire gets to RESONATE a BAD VIBE at your steady,gas-miserly-highway speed (those road repair patches every 10 ft MAGNIFY) , that is the "perfect storm" for bouncing ,causing cupped wear evenly and distributed in a "pattern" around said crappy tire. If NOT this THEN goto looking at a REAL suspension problem