Forza 3 racing classes

Each car is ranked by classes, from F to X and R classes from R4 to R1. R classes are real race cars that you can use and do few mods to it. R4 class would be like a racing Porsche and R1 class is close to formulas. There whole body is modified for weight and big down force to keep the car on the track when you try to get around a corner around 100 MPH. When it comes to Stock car like Nisan 370z the car is in D class for its rank, but if you start adding parts to it the rank goes up. D class goes up to 250 and if you would add something like different tires and they add 25 points then that car moves up to a class C. Then it would be 275 C but C goes up to 400 so if you would to race that car in C you wouldn't have chance of winning a race. So to be competitive you have to make your car the best you can. Play with is and tune it. It depends what you want, to use to stack up those points up to 400 C class. Do you want to add horse power or down force. You need horse power, but having a grip is really important. What I do and a lot of people when they create there car is add so much horse power to be competitive but also have that grip and down force i need to handle that certain car in corners. So if I use Nisan 370z, i dont want to add additional 400 horse to the car and then all be having trouble staying on track. Only good thing would be in straight away. I like to put sticky tires, change the suspension so i don't get much body roll and bit more in depth like if its rwd (real wheel drive) add spoiler and add down force and change front bumper for down force in corners to keep pressure on front tires so i can turn and not slip of the track. Other is weight reduction, and when i have the grip and down force i want i put up the horse power as much as i can. People have to choose power over control of the car. I like to have horsepower but i also like to keep my car on the track. Here are some pictures of cars that are stock from the game and that are modified.