[cam2Xrunner]

Bring it to a tire shop and have them balance the tires. If balancing doesn't help you might have a seperation or they need to be "road force" mounted and balanced. It shouldn't cost more than 25 bucks to balance all 4 wheels. Road force balancing will have a higher charge.

 

[cam2Xrunner]

And it is harder to balance larger wheels-17" and up correctly. Make sure that the shop does a "Dynamic" balance in which they set wheel weights on the inside edge and as close as possible to the outside edge of the wheel. And make sure they have an electronic balancing machine and not the old fashioned bubble type(I don't think anyone still uses them). If that doesnt fix it check for other things like what bdeuce said.