Go to the interstate service station and prepare for the race. Duing the race itself, take note that avoiding collisions is much more important than getting a lead. Activate Franklin's special ability to be able to catch up with the fast cars.
Once you've switched to Michael riding a bike, move closer behind the righ-hand car and keep up on his tail for a few miles.
Finally, you will take the wheel behind the car again. Swap to Franklin for the finish back home. Use his ability to gain a considerable amount of lead to both Trevor and Michael.