I have a mph app that I occasionally turn on and let it display speed while I'm driving on the highway. 70 on the dash display is really 75, 80 is about 86. I have to set my cruise around 75 to mostly keep up with traffic, which is really 80/81 mph.I’m curious for those who have bigger tire diameters than stock how do you monitor your speed? I have been using Waze/iPhone speedometer app but I’m not sure how accurate those are.