at highway speeds, anything above 45-50 mph, I get noticeable chassis vibration, sometimes I can feel it through the wheel, sometimes not, but I can definitely feel it in the seat. I replaced the tires, no difference. I replaced the tires AND wheels, no difference. I reduced the tire pressure a bit, no difference. The car only has 60K miles on it, so I'd think the struts/bearings would be fine.

Is this a common problem with this model? I've not owned a Honda before, and I have to say I'm a bit disappointed with the ride quality, though it's ok around town.

Any thoughts? I'm genuinely stumped as to what might be causing it. Actually sort of thinking about trading it in, since I'm getting tired of having to fool with this problem. I spend 40-50 minutes a day on the interstate, and it's getting pretty old.