Class 1

The cars used in Autograss racing are small hatchbacks, which undergo certain modifications. As per Autograss regulations, these cars have their trim, dashboard and seats removed. The engine is typically kept standard with limited modifications allowed, such as a reboring of up to +60. The engine capacity is restricted to 998 cc, except for Mini's engine which can be modified up to 1058 cc.

In separate races, junior drivers aged 10–16 are permitted to drive class 1 cars. Initially limited to Mini's standard 1000cc, the eligibility of this class has expanded to include cars like the Peugeot 106,^[2] Nissan Micra,^[3] Toyota Yaris,^[4] and Citroën AX^[5] since 2006. To accommodate the rising costs and scarcity of classic Minis, other experimental cars are being added to the list. The purpose of class 1 racing is to maintain an entry-level class with affordable construction costs. Ideally, the initial investment should be under £500, and the running costs should be minimal at the club level. However, cars that are competitive at the national level and capable of winning races often cost around ten times the aforementioned figure or even more.

Class 2

Class 2 in Autograss racing encompasses Front-wheel-drive or Rear-wheel-drive vehicles equipped with a 1300 cc engine. These vehicles can have their engines placed either at the front or the back. The commonly observed models in this class are Vauxhall Nova, Nissan Micra, and Ford Fiesta. The inclusion of front-wheel-drive vehicles in class 2 has made the Vauxhall Nova particularly popular among drivers. However, the use of 1275 cc Mini and Geo Metros are not allowed due to a minimum length requirement and the restriction to two-valve per cylinder cars. To ensure fair competition among the diverse range of vehicles used, a restrictor is fitted in the inlet manifold to balance their performance.

Class 3

This class represents the initial category with unlimited capacity in Autograss racing. The cars in this class are required to have front-mounted engine and rear-wheel-drive. It allows for the conversion of front-wheel-drive vehicles to rear-wheel-drive and permits the use of 16-valve engines with a maximum capacity of 2065 cc, while engines with two valves per cylinder have no displacement limitations. As a result, this class features lightweight and high-speed cars with considerable power. Among the vehicles commonly found in this class are Toyota Starlet, MKII Ford Escort, and Ford Anglia.

Class 4

Class 4 is a modified category in Autograss racing, permitting engine capacities up to 1130 cc. While various engine modifications are permitted, turbocharging and supercharging are not allowed. The rules require that the original engine and its position should remain unchanged, but extensive modifications are made to enhance competitiveness. Cars commonly found in this class include Mini, Hillman Imp, Citroen Saxo, Nissan Micras, and Peugeot 106.

Class 5

This category serves as a popular entry point for individuals interested in driving modified saloon cars. It permits engine capacities ranging from 1131 to 1420 cc, without requiring the use of the original engine or its original position. Many cars in this class use rear engines to enhance traction and grip.

Class 6

Class 6 is designated for vehicles with unrestricted engine capacity and modifications, specifically for front engine and front wheel drive configurations. The cost range for participating in this class typically falls between £1500 to £40000

Class 7

Class 7 is exclusively designated for rear-wheel-drive vehicles. The engine capacities in this class are unrestricted, but they must exceed 1421 cc, unless a motorcycle engine is used, in which case a 1000 cc engine is permissible. A considerable number of class 7 cars utilize motorcycle engines and in such cases, two engines may be employed to propel the vehicle. The engines used in these cars often come at a substantial cost, and examples include Cosworth turbo-engines, large-block American V8 engines, and various highly tuned V6 engines.

Class 8

This class is recognized for its high level of competitiveness and imposes the strictest limit on engine capacity, allowing a maximum of 1420 cc for car engines specials and 1350 cc for bike engines. Engine tuning is permitted, turbocharging or supercharging are not allowed. While the majority of cars in this class are designed with rear engines, this configuration is not explicitly mandated by the regulations; however, it is considered the most effective approach for maximizing weight distribution over the wheels.

Class 9

This class has a strong track record of success in open-class races. It combines the powerful performance of modern 2.0 L engines with the advantage of being lighter, resulting in superior handling compared to the heavier class 10 vehicles. The allowed capacity ranges from 1421 cc to 2070 cc, and extensive modifications are permitted, with the standard exclusions of turbocharging and supercharging. All cars in this class are equipped with mid-engines, and the majority of them utilize a transverse gearbox layout combined with rear-wheel drive.

Class 10

Class 10 is recognized as one of the high-performance categories in Autograss racing. It is another purpose-built class that sets a minimum engine capacity of 2071 cc without an upper limit, allowing extensive modifications to the engine (with the exception of forced induction for motorcycle engines). Twin bike engines within the capacity range of 1550 cc to 4000 cc, as well as V8 engines, are popular choices in this class. Class 10 offers an opportunity for racers on a budget to obtain significant power for a relatively modest investment, although some car builds can exceed £50,000 in budget.

Junior Specials

This class comprises single-seater vehicles equipped with nearly standard 1.2 L Vauxhall Corsa engines. Similar to the junior class one saloons, class one single-seaters are designated for drivers aged 10 to 16 years.

Other classes

Some specific clubs feature additional classes, such as the F600, which were introduced as a more affordable and less powerful alternative to provide easier entry into the special classes. These vehicles are equipped with single 600 cc engines positioned at the rear, transmitting power to the rear wheels. While predominantly utilized by smaller clubs, F600s can be found in various locations.

Another class is the stock hatchbacks, where nearly standard saloons with a maximum capacity of 1600 cc are used.

However, these classes are not officially recognized as stand-alone categories by the governing body (NASA). When participating in races, they are required to compete in Class 8 or 9 for F600s and Class 6 for stock hatchbacks.