Model X uses different size tires on the front and rear and the tires are directional, so the tires cannot be rotated.
The vehicle ride quality and handling are maximized when all 4 tires are the same age, model, and tread depth. Tesla recommends replacing a tire if any of the tread depths are 4/32 in. (3 mm) or less.
If only 2 new tires are installed, the new tires must be installed on the rear of the vehicle. In wet conditions, the tires that have less tread have less traction than the new tires. Reduced traction at the front of the vehicle leads to understeer, which most drivers are better able to react to than the oversteer that would result if the worn tires were on the rear of the vehicle.