I have had two 14 Silverado's and haven't really notice it. One 5.3L double cab built 9/13 (10,500 miles) and one 4.3L Crew cab built 11/13 (400 miles), both out of Mexico. The 5.3L had Continental CrossContact LX20 w/ EcoPlus Tech (nitro filled), the 4.3L has Goodyear Eagle LS-2. Both are on the 20" Texas edition wheels. Both ride very smooth on the highway. I thought I felt vibration on the 4.3L w/ Eagle LS-2's for about 5 seconds while going 73 mph around a highway curve. I read this and other forums for about a day and was freaking out! I've tried to replicate the vibration (which feels like a balance issue) again and have not felt it since. I've tried 4cyl and 8cyl mode and it still rides smooth. I know this doesn't help y'all's situation, just thought some addition info on other's wheels and truck my help ease (or further frustrate) someone mind. I think the continental tires feel like a smother ride even though I had the inflated to a higher pressure 35-38. The Eagle LS-2s are steady at 31-32 psi. Good luck to everyone with issues!