Not in a long time lol. I guess a better way to ask the question would be if there is any tire growth at 40mph. Low pressure bias tires tend to grow with rpm. Probably not much at 40mph though.
The 27" Terrabites put the speedo within 0.5-1mph of my Garmin GPS. I sat down and did the math before I bought tires, figured if I was going as fast a the speedo said if be happy. It worked out great.