RE: lining up painted stud?
Dave...if the tires are worn close to the wear bars, then the vibration is most likely due to OOR condition.....they are no longer "round", believe it or not.
Like Brad said, typically, the rear wheels can either rotate on the rim slightly, since they are the drive wheels, or since they rode out back, they may have been out of balance for a while, but since they were "back there", you didnt notice any vibration....then if they were in fact out of balance back there, that can/will cause uneven wear patterns on the tread cap.
Rotate the rears to the front, and you will now feel the vibration, and most likely it wont go away until they get replaced.
when a new set of tires is first installed, typically, the wheel/tire package that required the least amount of weight to off-set the difference in balance, will get mounted at the driver's front. This is because that tire/wheel position is closest to the driver. We would mount/balance all 4, and then work our way back/away from the driver according to the amount of weight needed to balance the combination.
LF
RF
LR
RR
...with the RR being farthest away from the driver.
also remember, when balancing a wheel/tire package, your balancing the rubber that is on the tire. As you drive, the rubber wears away, and this can ultimately change the balance. 90% of the time if you put a wheel/tire combo on a wheel balancer, you will find that they are out of balance. This is because of what I wrote above...the rubber wears away, thus changing the amount of weight required to balance the wheel, and the location of the wheel weight.
I hate to tell you but, the ride wont be perfect until you get new tires. Also remember, tires are balanced in OUNCE increments. On a truck/SUV, you can actually pick up a stone/pebble between the tread blocks that can weigh more than the wheel weights on that wheel...this too can affect ride quality.
Lastly, I would check to make sure they were re-balanced correctly. many shops dont remove the old weights when they re-balance tires...they will simply hammer on a new weight in a different location to compensate, as the machine is only trying to balance the rotating assembly. This is known as 'counter balancing", and is a common no-no amoung lazy tire shops.
This discussion is something that many tire companies take in to consideration when they build a tire...often, the molding process can help promote better tire wear to elleviate a future balancing problem. Segmented mold tires are known for better future balancing as tires wear. Segmented meaning the tire was molded together like a pie...piece by piece, as opposed to two halves being molded together at the center tread seam. Most truck tires or larger passenger tires are non-segmented mold, and can often wear uneven over their tread life, thus changing the balance constantly.
