My approach to unlocking this achievement was to use the MV Augusta: Rivale 800cc
bike from the Naked Bikes: 700cc - 900cc
This bike lets you compete in the following Track Day Race:Naked Bikes: Middleweight GroupNaked Bikes: Over 700ccEvent 5
I was no-where with an un-upgraded bike, so be prepared to spend some credits on modifying your bike, but by doing so you will unlock:
The Personal touch achievement in RIDE worth 11 pointsBuy a new component for one of your bike
I didn't want to spend too much money as I was also after The Collector achievement, so decided to upgrade everything on the Engine and the Transmission, I also added a light set of wheels and upgraded tyres. I did not spend anything on brakes or suspension.
I also used the same bike with the same upgrades to unlock:
The Bite my dust! achievement in RIDE worth 27 pointsWin a gold medal in a Drag Race event of the World Tour
You may want to spend money on upgrading the brake and suspension elements as it will make things far easier as this event can be slightly tricky, it took me 3 attempts to pass 24 bikes and needed fairly perfect laps to do so,
I would suggest you need to be passing the 15th bike just after crossing the start finish line for the 2nd time in order to get to 24 in the time allowance.
(A couple of times I was passing 14th, by or just before the start finish line and that wasn't good enough)