I had a road force test done at my Lexus Dealer due to random vibration and had 2 tires that where out of round I got 4 continentals from Discount some time ago and put 23,000 miles on them but were noisy and a bit harsh.

Boy am I so dumb, I never though tires could cause such random vibration even with little damage to the structure deep inside the tire that were so small even if they are properly in balance. I kept thinking that there was something wrong with the car suspension or ball joint, etc, since the problem popped up 3 months ago all of a sudden and I even rotated the tires with almost 50% thread left.

Discount gave me 4 brand new Bridgestone Potenza RE960 AS Pole Position the number 1 tire rating on Tirerack for 400 dollars!!! Amazing deal! Got rid of the continental contipro contacts! I fought for those tires since they were not honoring the 4 replacement cercificates for all 4 tires since only 2 were defective and the remaining 2 where given half credit for. Since its an AWD, you have to replace all 4 tires at same time.

No more of that odd vibration on certain roads. The last 3 months were hell for me.

 

Tires are mass produced and do have some quality defects from time to time. Glad your vibration problem is now gone. Now you can enjoy the comfort of your 3GS as you should.