Remember this one piece of info ... and you will understand why customers get angry, tech's get frustrated and shop owners pull their hair out with repeat vibration issues !
" Balanced ... " does not always equal "smooth ... " And a vibration is not always a symptom of an out of balance condition.
Road force variation causes most vibration issues, not poor balancing. Road force variation is like a mattress with a lump in it ... every time you roll over the lump, you feel it. Your tire, when it is manufactured, has a very small lump as a by-product of the way it is put together. And every time the tire rolls over that "lump ... " , there is the possibility that it can be felt in the car. And, unless a shop has an extremely expensive road force balancing machine, and the time, patience and training to use it properly ( it takes roughly 4X as long to properly road force balance a tire, and even shops that have the machine typically only road force balance on come-backs ... ), then they have NO IDEA !!! if a vibration is balance or road force generated. All they know is that you the customer are not happy, and they get to try again, for free. And they hate that ... !
You can balance a severely bent wheel / tire, with enough weight. It will spin out to 0.0's , and be perfectly balanced ... but it will definitely not drive smooth. And you can take it back a second, or third or whatever time, and it will again be balanced, but not run smooth ... EVER.
Your wheel / tire assembly is like that bent wheel ... every wheel, if measured precisely enough, is out of round. And every tire, again, if precisely measured, has a low/high, or more likely, a stiff spot (that "lump " we mentioned earlier ... ) What you want to avoid is putting the high/stiff spot on the tire at the high point on the wheel. You want to put the high/stiff part of the tire at the low point of the wheel to cancel out the two imperfections to the greatest degree possible. How do you do that ?
Well, car makers want their new car to be as smooth as possible. So they measure every wheel, discard / return those that don't meet their specs, and, very importantly, mark the low spot on the wheel before ever mounting a tire. The low spot is marked with a sticker, a paint mark or even a dimple in the wheel. Same with tires. All are measured, and those that meet the oem specs (usually much stricter than aftermarket tires ) are again marked, typically with a red dot showing the high / stiff spot on the tire. When the tires are mounted on the wheels, they match the high / stiff spot of the tire to the low spot marked on the wheel, and often re-test the wheel / tire assembly to triple check for smooth operation.
And that is the problem when you dismount your factory tires, and get new tires mounted. You don't get that absolute focus on smoothness that the car maker obsessed about, for a number of reasons. First, if your wheels are not permanently marked at the low spot, then you have lost this key piece of info going forward. There is no way to optimize the wheel / tire placement. Second, your replacement tires may not be as round / uniform as the original equipment tires, and may not be marked the same way. Third, the tech mounting and balancing the tires may not understand / not been trained / not care about any of this info. So random luck can play a factor.
My simple advice for a vibration ( note I didn't say "balance ... " ) issue is this. First, see if you can isolate the problem wheel / tire assembly by moving wheels from front to back one side at a time, if your wheels tires are all the same size. Assuming you have figured out which wheel it is, do the following: Leave all weights on the wheel, and spin it on balance machine ... if it shows as balanced, or fairly close (put a wheel on 3 different balance machines, and they will probably all read slightly different ... ), then chances are it is not a balance issue. Most shops, if you ask them to re-balance the wheel, will remove the weights, then balance the wheel again. If balance looks ok, then break the bead of the tire and rotate tire 180 degrees (half-way) around the wheel. Re-balance and road test. This more often than not cures a road force vibration issue by moving the stiff spot of the tire away from the high spot on the wheel ... which thru simple random luck ended up poorly aligned.