a lot of times the cupping is caused by bad or worn shocks
and the tire is just bouncing off the pavement. I also agree with Wild Bill. I had a problem with a left front tire (Michelin) where it was wearing diagonaly all around the tire. took the truck in to have it aligned and the mechanic said it looked like the belts separated.
said the front end wasn't that much out of alignment,but i also had him do a rear thrust alignment. the tire only had about 30,000 on it took it back to the tire dealer,and had it replaced.of course he was saying it wasn't belts separating. said he would have the michelin rep. look at it. well guess he decided they still wanted our business because we were never charged for the new replacement. i myself like the michelin tires have new all the way around and with the new thrust alignment haven't seen any signs of abnormal wear.
as far as trucks go my FL-70 ridin like a cadillac.
Good Luck,
Fr8 Shaker