2006 Silverado Crew Cab Z71 Frame Beaming issue

[scottmoyer]

I have an issue that I can't seem to put a resolution to. When I bought my truck new in 2006, it rode very smooth on the the 265-70/17 Bridgestone tires. I got about 30k miles out of them and purchased the BFG AT KOs in 285-70/17 in 2008. My truck shook and bounced all over and I got two sets from the tire center before Michelin replaced them a third time with the 285-70/17 Michelin LT AT2. I got about 70k miles out of those tires with a smooth ride.

 

Being that I didn't like the look of those tires, I decided to try the BFG tires again in the oversized 285 series. These were great looking and great riding tires. I only got 30k out of these tires and replaced them again with the Michelin LT AT2 since I got so much better mileage out of them. I had these Michelins in the shop every weekend for a 5 weeks getting rebalanced due to shaking of the rear at 45mph and above. The tire shop suggested that I go back to the BFG tires thinking that I was looking for a reason to get rid of the ugly tires. I did put the BFG back on and love the look of the new style AT2 tires, but anything over 45 is a shake fest.

 

I moved the rear tires to the front to verify that the tires weren't out of balance and the issue continues.

 

Why am I experiencing the frame beaming issue with only certain tires? I could drive 80-85mph with the last set of BFG tires in a Cadillac like ride. What can I do to fix this problem without adding 200# to the rear end?