No calibration. But, it does re-read the trailer length the first time you make a significant turn after start or selecting a trailer. Since the truck doesn’t really know the angle the trailer is at, it will come out differently depending on the turn, etc.
My TT is 29’ +\~ and comes up 30’ most of the time, a few times Max or 20’ (which i think is really 20-29).
My 16’ cargo trailer (21’ long) has a 2’ deep v-nose, and the truck gets it right 2/3 of the time; the rest of the time, it it doesn’t even register. If I stop, disable and the enable the system, and then make a tight 360’, it gets it right.
