Okay, this is what the mechanic said when I emailed him,
"Both of your rear wheels were bent, one was not bad, the other was more
noticeable (cant remember off hand which side was worse), they both balanced
out. Like we talked about, as you are driving... the tire is not round, it
takes the shape of the wheel, and over time becomes more pronounced, which
means they will require more balancing to keep the vibrations down. Also the
lower end tires seem to be more prone to this kind of sensation (road noise,
balance, flatspots, etc.), regardless of straight wheels or not. Slight
vibrations seem to develop at highway speeds. Another thing is with our
roads here, and hazards it is easy to bend wheels, driving through pot
holes, obstacles, etc. One last thing, with ambient temps as hot as they are
if cars sit on hot pavement all day in the blazing sun, or even for a few
days (such as an airport stay) you can develop flat spots, usually after a
few minutes of driving this becomes better. Hope this info helps, and see
you soon."
The vibration was present on the old tires and was very bad, and now on the new tires but is very slight. This makes me think that the problem it is not so much the tires but the wheels.
For clarifications is had Pirelli PZeros on before and switched to the Kumho all weathers. The wheels are 18" as well.
Randall - I would have no problem with changing the tires but I just had them put on. They have like 300 miles on them.
Harmonic Vibration
Hybrid Mode
