Bought a set of mich. 285x65x16 and after about 15k miles noticed that at about 50mph had vibrations in two of the tires.As you increase you'r speed the vibrations go away. The tire shop told me that the tire had a wobble and it took exessive weight to balance the tires.I have had the tires too long to get a replacement also they said that the narrow factory wheel was also a factor. Can't belive it, any one had this problem?

If you're running on the stock 16x6.5 rims that could very well be an issue. My 3500srw came with 265/75 on 16x7 rims so apparently they felt even the 265's needed a little wider rim.

Could be a broken cord in the sidewall.

I recently got new 285/75/16 Toyo Open Country AT's on my 16x8 wheels and picked up the exact vibration at 50 mph, but it was immediate. Before them I had 285 BFG AT's than never did it. I took the truck back to them after about 2 weeks and they radial force balanced all 4 tires and added quite a bit more weight to most, if not all, tires. Of course they drove the truck before and after and said "Yep, that fixed it" and handed me the keys. I felt the vibration again as soon as I hit 50 mph.....go figure. I never bothered taking it back again because they balanced the tires right there in front of me, checked for out of round and everything looked good so I've just chalked it up to the dreaded "frame beaming" that these trucks are famous for. I will be keeping an eye on this thread to see what other replies you may get.