Shaking issue at highway speeds

Hi guys, i've got a 1999 acura 3.2 TL with 172,000 miles. Just bought
it from a guy that has maintained it very well and im quite happy with
it.

The only issue that seems to be bothering me right now is that when im
driving above 50 or so, the steering wheel shakes a bit like its not
aligned or something is off balance. Occasionally it doesnt shake at
all... very smooth. I drove on the same road a couple times to make
sure its not a fluke and most of the time, it shakes, but once in a
while it doesnt, so its not road conditions. I have a pretty sensitive
feel when driving so I definately notice the difference, but people in
the passenger seat probably dont. What could be the possible cause,
where do I start to look first? (Cheapest to Most expensive options)
I'm a DIY guy and i've got alot of experience with auto body work, but
not with motors, electrical, and suspension.

Another issue is at above 40 miles the rear starts humming, a bit
louder than i'd like, is it okay to keep driving for a while? i'm not
sure if its the right side or the left but im pretty sure its the rear.
My friend told me its the rear wheel bearings/hub. How do I Test that?

Thanks everyone.

 

Does it hum and shake at the same time? Could be a bad tire doing both.

 

No, I changed the tires, I dont believe its a bad tire.

 

Be sure the tire is on the rim corectly and in balance. Check ball
joints and steering linkage for play. bob

 

As on my TL-S, I have directional tires. Are you sure you do not have a
left on the right or vice-versa? Does sound like a tire issue.

 

need to take each of the wheels off one by one and carefully inspect the
suspension. if you have a shock out, that'll do it. same for a bushing
or wheel bearing. make sure wheels are properly mounted, not bent or
dented, and torqued correctly.

 

what do you mean "shock out" ?

 

shock absorber not functioning correctly. like light out.