What is the approximate rolling diameter of a 26x11.5/16 ET Street with about 18 psi in it and typical F-body weight on it? Diameter is listed as 26.2", but that's without any weight on it.

TIA for any help

Static weight means nothing. Once the wheel is turning at speed it will expand to overcome the weight pushing down on it. The total circumference is the same if it's on or off the car.

Pull the wheel off and wrap a measuring tape around it.

Okay, what kind of "speed" are you talking about to overcome the weight of the vehicle? You can look at a car driving along the interstate at 80 mph and see the "flat" spot of the tire on the road is similar to if the car were sitting still. My guess would be well over 100 mph for the tire to even start to grow and overcome static weight. We're talking about a 12 second street car here with radial or bias ply tires, not a top fuel car with wrinkle wall slicks.

Why pull a wheel off to measure it? Seems a lot easier to just roll the car a few feet, use a couple chalk marks on the floor, measure and divide by pi. Of course that method only gives you the actual rolling diameter with static weight on the tire, not "advertised" diameter, so maybe I'm missing something.