Just as much as I need. So I can feel the joy of accomplishment and play your game again. ;)
You can calculate if the player will be able to reach the finish line on time. You can customize difficulty for the player. It’s no use playing more if I lose one or two tires in the beginning.
That's a good point, I should have put more tires in the beginning so the player can get closer to the finish line each time. Great feedback, thank you!