Page "Touring car racing" Paragraph 4

While rules vary from country to country, most series require that the competitors start with a standard body shell, but virtually every other component may be allowed to be heavily modified for racing, including engines, suspension, brakes, wheels and tires.

Aerodynamic aids are sometimes added to the front and rear of the cars.

Regulations are usually designed to limit costs by banning some of the more exotic technologies available ( for instance, many series insist on a " control tyre " that all competitors must use ) and keep the racing close ( sometimes by ballast weight where winning a race requires the winner's car to be heavier for subsequent races ).