You don't actually have to beat the rival, just play rivals in a 2017 car.
What I did was I pressed the menu button, went to 'RIVALS', then chose 'MY RIVALS'. Only one race available for me so I chose that. It was an S1 class race on a dirt track. I selected the 2017 Ford F150 Raptor HE to race with. After two laps it was clear that I wouldn't get near the time of my rival, so I went to the menu and selected 'QUIT EVENT'. The achievement popped.