I have seen several posts concerning stock Model X tires. Here is what I did to increase range and provide peace of mind when traveling while maintaining the stock appearance of the car.
I am using 5 245x55x19 Michelin Premier LTX tires mounted on 19 ' Model S slipstream wheels. I have used 1/4" spacers behind the wheels to bring the wheels out somewhat for looks, but they worked fine before I installed them. I own a 5 passenger 100D Model X. I rotate all 5 tires. The spare is stored in the compartment behind the back seats. The spare makes the cover sit higher and required some minor modifications to make it stable etc. I have 13,000 miles on the car and have averaged 318 wh/mi, which means my range is over 300 miles. According to the records from my first year service at 12,600 miles, the 4 tires on the car have 6/32'' tread on the front two and 7/32' on the rear tires. They measured 8/32 " when new. I have rotated them twice so far. I am driving 50% of the time 70 MPH plus on the freeway. I carry a small "bottle jack" and lug wrench. I picked up a nail 600 miles from home in one tire and was able to change it and be back on the road in under 20 minutes. It was repaired where I had the tires mounted for free when I got home. These may not be for everyone, but work fine for me. They are "only" rated for 130PMH and have a sightly lower weight carrying capacity then the stock tires. I find the higher profile makes these a good choice if the roads you travel are not in the best shape and you want greater range. If you are towing a lot and/or own the heavier 6 or 7 passenger X these might not be for you.