These guys seem more than a little nuts to pass on the shoulder at over 185mph (299kph) on public roads. I think for "safeties sake" the manufacturer limited speedo to 299kph but tac kept climbing once speedo was pegged at 299kph. With the right equipment in my youth I might have tried it once while knowing all along it was a very foolish thing to do. Not today. TW @ 55mph suits me fine.