Super farm tractors are the closest to "on the farm" tractors in competition. Originally they had to retain the original gearbox and rear axle, however now component (tractors with rear axle and gearbox from a truck, stronger and lighter) machines are allowed. Superfarms are limited to a maximum engine size of 405 cubic inches (6.6litre). They can only run a single turbocharger, albeit of any size, and must use diesel fuel only. Tractors with an engine size of less than 6 litres are allowed to run at 3200rpm, whereas engines larger than 6litre up to the maximum size can only rev to 3000rpm. They compete at 3500kg. Power estimates to be in the region of 500hp-800hp. The super farm class is generally considered the introductory class to the sport.
Supersport tractors follow the same rules as the superfarm class, however performance rules allow a maximum engine size of 549 cubic inches (9 litre) at 2700rpm, or at 510 cubic inches (8.3 litre) where they can run up to 3200rpm. They can only run a single turbocharger, albeit of any size, and must use diesel fuel only. These tractors compete at 4500kg. Power is estimated to be up to 1800hp, but with relatively low RPM torque is extremely high!
Limited Prostock tractors follow the exact same rules as Superfarm tractors, however there is no RPM limit. These tractors compete at 3500kg. Power is estimated to be up to 1500hp.
Prostock tractors are limited to a maximum engine size of 510 cubic inches (8.3litre). They can only run a single turbocharger, albeit of any size, and must use diesel fuel only. There is no RPM limit. These tractors compete at 3500kg. It is not uncommon to see these tractors generate 2500hp.
Limited Superstock tractors are limited to a maximum engine size of 466 cubic inches (7.6litre). These machines are basically Prostock tractors, however they rely on spark ignition as they run on Methanol fuel. There is no RPM limit. These tractors compete at 3500kg. RPM can be in 7000+ range with power estimates anything from 1500hp to 2500hp.
Superstock tractors are limited to a maximum engine size of 650 cubic inches (10.65litre). They can only run up to four turbochargers of any size with a maximum of three pressure stages. Tractors can use either diesel fuel or methanol fuel. There is no RPM limit. These tractors compete at 3500kg. Diesel Superstocks generate in the region of 150psi boost pressure at 5000rpm. Methanol Superstocks tend to run lower boost (70-80psi) but higher rpm (7000+) Power estimates anything from 1800hp to 4500hp.
Modified tractors can use any gearbox and any rear axle. There is generally no engine, turbocharger, fuel or RPM limit. Modifieds may add or remove engines to compete in different classes as they can compete in Light Modified (2500-2700kg), Modified (3500-3700kg) and Heavy Modified (4000kg). Modifed tractors are the most spectacular in all Tractor Pulling, where some heavy modified tractors can generate over 10000hp.
