I know they have to read higher than you are doing but at 100 road angel reading the speedo says 115 ,this seems to far out to me ,plus when my father in law follows his reading is only just out compared to the road angel unlike mine what is miles out .same with my van when i use it in that 80mph in my van gives a road angel reading of 78 ,would try it at higher speeds but there are no hills steep enough for long enough :P