Nissan actually a technical service bulletin on this for the z-sports car.. I think it was the 370z. They talked about removing all the stones from the tread before balancing the tire, that mass could affect the balance. I thought I'd try that on my scion tc, and I actually got about 3oz of weight from the stones in the tread! That definitely could affect the balance. So nope it's not nuts when you're balancing a tire or if you suspect the balance is off, check for lots of stones.