DBoz, mate, there is something else going on with your Genesis. Here is why I do not think it is due to the tires: I cannot reproduce your issues with my car, and I have different wheels and tires. I have two sets of wheels (stock 18" for winter and staggered G80 Sport 19" for summer) and several sets of tires because I do a lot of mountain driving: Michelin Primacy MX5 (worst tires on the planet), Vredestein Quatrac 5 (amazing), Michelin X-Ice (amazing), and Continental ProContact TX (okay). In no case does the car vibrate at high speeds on any of those. In fact I once went 119 mph and only heard a dusting of wind against the car. I read your posts on the previous page that your car will vibrate at idle on a steep decline? Mate, I can barely
hear my car at idle, let alone feel it vibrate. The good news is that your issue is uncommon on a Genesis, the bad news is that you have to figure out what that issue is.
I can sympathize with you because I am experiencing the same intense frustration but with a different problem. I installed an
oil catch can on my Genesis and on my wife's Tucson. Whereas the Genesis has
little issue with the
catch can, the Tucson is having lots of problems with it. Spent oil/fuel vapour is somehow getting into the duct system and infiltrating the cabin, sickening her and I. I have gone back to the installer four times, I moved it, I changed the o-rings, have switched cans, have cleaned it, have used chemical sniffers, I have thrown a lot of money at it, have argued with the distributor over Email about it, have had to take her car when she needed it to others for a second and third opinion, had to be on the receiving end of her irritations and my own, have rifled through pages of internet forum comments about vapour getting into the cabin, and
like you I still cannot get a solution to the problem. The mechanic recently told me to just get rid of the can on the Tucson. So, I
know right now
what you are going through.
I don't know the extent to which you have been meticulous about this, but yes, I would agree with others -- you need to get two or more other opinions with professionals, get in touch with a Hyundai engineer somehow, and if they do not have a solution, get rid of it. If you like the Genesis, the chances are very small you will have the same problem ever again when you buy another Genesis. If you are too frustrated at Genesis and want out for good, buy another brand like a Lexus.
Oh, and by the way, my degrees are in physics and I work in applied physics. When these so called service "managers" say gravity pulls harder on the car than others, they just mean that the car weighs more. They are not being profound. You can just say that the Genesis is pulling the earth towards its center with exactly the same force by Newton's third law. Still not profound.