Here are the weights of the A/T3 for 17" wheels as provided to me directly from Cooper last week in case anyone is interested:
The Lt275/70R17 (E), (C), and Lt285/70R17 (E) Cooper Discoverer A/T3 tires should weigh the following listed weights:
LT275/70R17 E A/T3 spec 5875 weighs 51.88 pounds
LT285/70R17 E A/T3 spec 5850 weighs 55.17 pounds
LT275/70R17 C A/T3 spec 5871 weighs 50.70 pounds
Interesting that the E only adds a pound over the C in the 275. FYI, I also checked the bad ass S/T Maxx in a 285 E, and was told it weighs a whopping 60 pounds. With its sidewall reinforcement I would have a lot more confidence in it over the 285 DuraTrac off road, but it is 7lbs. heavier.