Earlier this month, I took my Explorer to Discount Tire for a tire rotation / consultation for new tires. The stock Hankooks are known for wearing quickly and the manufacturer prorates for it. Anyhow, I go out with the advisor as he checked my tires and he noticed that my passenger side tires were 4/32nd while the drive side tires were 5/32nd. I always rotate between 5k-10k, front to back at DT. When I asked him why they didn't wear the same, he responded that the axle lengths were different and that causes uneven wear, left to right. Not sure if this is true but he said it like he had been asked that question before without hesitation.