Speedometer Check -Trail Tech Endurance II

The last of five 4 mile loops to check calibration of the speedometer. Over a 20 mile run around a 1 mile square block. It was 58 yards off in 20 miles but I cut the corners a bit. That could have amounted to 12 yards per mile. 8.7 Ft. per corner, that works out to a 5.5 Ft. Radius at the corners though I didn't really try to square it off. Sounds about right. I'm going to say the speedometer is pretty dang accurate.
The magic number I'm using is 2122 for an 80/100-21 tire.