[Tito]

With modern radial tires flat spotting only occurs if the car has been sitting for a really really long time or if you have pretty soft high performance tires on your rig. This was a pretty common thing for bias ply in the good old days tho'. If you take your tires to the local tire dealer have him show you what it looks like when they spin balance them on the machine. Flat spots are pretty obvious. Also check your air pressure. On some low priced brands a little loss of air pressure with cause them to vibrate. If you have done all of this then the last step is to see if the wheels are true. The tires will have to be dismounted and then the wheels spun on a balancer to see if that is the problem. I hope that this helps. : )