High speed vibration, 22 inch wheels

[Soulshine10]

Back in march of this year I bought a 2015 SLE 5.3 Liter with 39K miles on it. Overall a beautiful truck and am real happy with it. The truck came with 22 inch wheels and brand new 285/45 R22 Goodyears. I made the dealer put on new rubber as part of the deal. I recently noticed at roughly 70 to 75 MPH I'm feeling a shimmy/vibration in the truck. I took it to my dealer, as I have a 12K/12Mo bumper to bumper warranty, thinking I have a wheel balance issue. To my surprise, the dealer tells me I have a bent rim on the left rear and 2 "bent" tires. Still unclear as to what a bent tire means but never-the-less I was not pleased and extremely skeptical as I have not hit anything substantial. I told the dealer, who I have done business with for quite some time that I have only had the truck for a short 4 months and I have not hit anything that could or should not bend the rim. Since its a small dealership I went right to the general manager and he tells me since I didn't purchase wheel insurance the repair is on my dime. I got him to quote it at his cost and no labor for a total of $612 to replace. Though he wouldn't guarantee the new rim would solve the vibration issue as his technician said the tires were damaged. I've only put 3K on the truck and tires. I looked at the wheel and cant see any damage Wondering if anybody has experienced something similar? I'm going for a 2nd opinion so I contacted a high end wheel and custom shop to try and balance it out. any thoughts/advice is appreciated. the cost to balance all 4 tires is $110.  photo of the wheel shown below

[Steveo_supremo]

These situations can be a real nightmare for the shop and for the vehicle owner. How did they determine that you have a bent rim and 2 bad tires? I'm assuming they have the latest and greatest road force balancer and a guy that knows how to use it? Were the wheels brand new when you bought the truck? Is it possible that one was already bent when you drove it off the lot? Also, if the tires were new, your dealer should be able to get them warrantied by Goodyear although it may be a huge hassle for them that they'd rather not deal with. 

[zmnypit]

FWIW this is the 2500 section. Theres a thread in the 1500 section as the vibration is known issue with 1500's. No one know the cause but several have claimed to remedy it. 

 

https://www.gm-trucks.com/forums/topic/153186-shake-or-vibration-issues/?page=802