my 2000 rl has only 44k on the clock and the stock bichelins

i just had the tires rebalanced and the alignment done, and it still vibrates a bit.
now they told me that the tread depths are a little diff. ont he front. could tht cause a vibration like i am getting.

it happens generally at highwqay speeds. sometimes it is so smooth but sometimes you can really feel it in the wheel.
any suggestions.
i also asked the garage to make sur3e nothing is bent, and they said everything was fine, cept the tread depth

 

sometimes the tires could be the problem. i know this guy with a GX470 had the same problem until he swapped out the tires

 

i was thinking about getting kuhmos and just replacing the bichelins.
everywhere i call, they don't give me much info, since everything else checks out. i may have to do that