Tires: Tire Problem, inflation pressure, tire warranty

Question
I have a 2002 Tahoe that I just bought and I have noticed that it shakes at highway speeds, (from 65 on up) I have taken it to a tire dealer they have balanced the tires and it is still doing it so they said it was a tire in the back that was bad you can feel it more in the seats then in the steering wheel and below 65 it drive smooth as can be. Can you please help me firgure out what is going on since I just bought this truck and I hoping that it is just a bad tire and not something more! PLease Help!!
Thank You,
Justin J

Answer
Justin,

This is most likely irregular wear.  Run your hand over the tire and see if you can't feel high spots and low spots.  Balacing is not going to fix this problem - only replacing the tire will.

This is caused by misalignment and aggravated bu insufficient inflation pressure and insufficient rotation prartices.  This measn the tire warranty does not apply.

So there are 2 possibilities:  Replace the tire at your own expense - or - live with it until it is time to replace the tires.  It is possible that the tire will gradually wear evenly, since the misalignment was probably in the front end, but that may take many thousands of miles - if it happens at all.