I thought I might throw out some of the reasons dual tires wear down unevenly/ get chewed up-- and maybe some of the mechanics could elaborate:

1) Over- Inflation
2) Under- Inflation
3) mis-matched inflation pressures
4) poor axle alignment
5) warped/bent rim
6) unbalanced tire/rim
7) loose lug-nuts
8) worn wheel bearings

9) Driver Abuse-- shifting in a turn
10) Driver abuse--braking/accelerating in a tight turn
11) Driver abuse--driving with air bags deflated
12)Driver abuse-- disconnecting- pulling out from under loaded trailer- without dumping air bags.
13) Driver abuse-- rough driving--bouncing trailer- rubbing on tires
14) mis-matched tire tread remaining
15) mis-matched tire tread type
17) mis-matched rolling resistance

torque arm bushings worn will do the same thing as well as faulty shocks

18- worn torque arm bushings - per ppc25
19) faulty shocks- per ppc25

ok, what would that look like- is there any special pattern of uneven wear that might indicate- point to the torque arm bushings? faulty shocks?

Like Over-inflated tires-- wear out the center and "cup" the tire
and under-inflated tires--wear out the edges more, right?

tourque arm bushing wear on the tire would cause the outer tire to wear out, also the way to tell is if the left bushings have gone it will cause the right tires to wear out at an incredibaly fast rate, and if its the right bushings then the outer left tire will wear out,
the bad news is that to change the bushings you need at leaest a 10 ton press to get those buggers out of the arm so its not a job you can do yourself like most, hope this is of some help to you guys out there.

actually you can burn/cut the bushings out with an acetylene torch; i just did my trailer a few weeks ago, old reyco 21b. i had to buy all the bushings and two equalizers, ran around 700 dollars. definitely worth it, though and i'm glad i did it myself. best labor estimate i found was 13 hours, at 65 an hour.

tankyanker i admire you for taking on such a task, how on earth did you get the new bushings back in? anyways 13 hrs labour is a good time and $65 an hour is pretty cheap, up here in Saskatoon Canada shop rate is always above the $100 per hour mark, still the main thing is you saved yourself a whole bunch a cash.

I myself came over from Great Britian a few years back and emigrated here did driving for a short while and decided to continue my apprentaship to gain my journymans certificate in truck and trailer mechanics.
Drive safe out there.

i actually dropped everything off with a friend who works at an auto body shop, so he could press all the new bushings into the new equalizers and torque arms while i was working ... and he couldn't get the bushings to stay in, even with a press, so when we were putting everything in, we just greased the bushings a little and drew everything up tight together with the impact. everything came together really well and i was even able to re-use all of my old torque rods. i put in the rubber/oem bushings ... i don't know if you would need a press for the polyurethane bushings, i really couldn't afford them.