Depends on tires also, but that is more of a constant due to rolling friction, not a function of dynamic pressure. Rivian has indicated a 10%-15% reduction in range for the 20 inch A/T tires. I assume Hummer 350 miles will be with the standard A/T tires. Rivian did come in a 6949 lb curb weight, which I believe was higher than originally predicted.
Highway range for R1T with 21 inch tires is 293, with A/Ts would be 250-264 with the 20 inch A/T tires.
Highway range for R1T with 21 inch tires is 293, with A/Ts would be 250-264 with the 20 inch A/T tires.