It could also be what they call 'run-out'. That's when a tyre is not perfectly round. I had a big problem with wheel vibrations on a Commodore. I got the tyres balanced and it still did not fix the prolem. Eventually I asked them to check if the tyre was round, and sure enough, as it was spinning on the balancing machine you could see that the shoulder was vibrating in and out as it was spinning.
This tyre looked OK in every way - plenty of tread and no obvious wear marks.
You could probably pick it yourself, if that was the problem, just by spinning the wheel on your car before you loosen any of the wheel nuts!