I discovered Shelby, my '17 is also afflicted with a speedo that is optimistic according to 2 gpses I own.
Zer0, my '14 was 5-6kmh fast mostly over the entire the range, dropping to about 3-4kmh fast @130+ kmh when compared to 3 gps units I own. Zer0 had alloys, Shelby has steel wheels. Both were 5mt.
Has anyone else noticed this or have a speedo that's off?