I've recently made one modification that seems to be helping. Tuesday of this week I went on a 250 mile trip. When I left home, driving about 65 mph, the vibration was bad, and I was dreading the trip. I started adjusting the air pressure in the tires, to see what effect that had. When I lowered the pressure, the vibration got really bad, so I started raising it. Since then, I've played with a lot of pressures.
I'm currently running about 38 in the front, and about 44 in the rears, and my vibration is minimal. It's still noticeable, but not very much. However, my tires (185-70-14) are supposed to carry a maximum of 35 psi. Also, I'm getting a rough ride from the over-inflated tires. I plan to drive it like I now have it for a few days, and see if the vibration remains minimal, or if it gets worse again. If the vibration remains minimal, I'm going to assume that my problem is somewhere in the tires, perhaps a defective sidewall that is not flexing uniformly.
