Modeling vehicle dynamics as a whole is a great subject, because there are so many parts where you have to explicitly decide on how much you wish to simulate. Brakes, tires, suspension, vibration transfer... On one hand you can have a simulated vehicle in 2 hours of coding, and on the other you can spend two months on tires alone.

One related story I like is how Assetto Corsa Competizione devs bumped into "weird" behavior emerging from their simulations which seemed like a bug - but then confronted with the actual manufacturers and found out that it happens in real life as well:

https://www.youtube.com/watch?v=PFxIZ-9Awj4

Highly recommended, video is titled "A traction control bug that was a realistic feature".

EDIT: And this is before you get to aerodynamics, which is a whole different can of worms. With todays GT3 cars, how you simulate the front splitter and rear diffuser can make or break the accuracy of the simulation. It's fantastic stuff. Wish I worked on this day-to-day. On the other hand I have trouble putting it down and going to bed when doing it as a hobby, so...