Tractor pulling is unfamiliar territory for some—a motorsport competition in which vintage and modified tractors pull a heavy drag or sledge along an 11m-wide, 100m-long track. The winner is the tractor that pulls the drag the farthest.
Noted as the world’s most powerful motorsport, Scotland certainly holds its own among larger countries, including the United States, Germany, Switzerland, the Netherlands, and Belgium, to name but a few.
The Scottish Farmer spoke to Graeme Simpson, director of the Scottish Tractor Pullers Club (STPC), and Richard Cross, vice chairman of the British Tractor Pullers Association (BTPA), to learn from their wealth of tractor-pulling knowledge.
Richard, from Hull in East Yorkshire, first participated in tractor pulling in 2017 after a Scottish friend introduced him to the sport. He is now a familiar face within the DieselRoss pulling team and director of Performance Sledging. Richard is a key asset to the team, bringing over 30 years of experience in farm machinery, following the sale of his own dealership, Northfields Agri, in 2018.
Q. What is the STPC?
A. Founded in 1985 by David Clarihew from Elgin, the Scottish Tractor Pullers Club (STPC) began after Clarihew witnessed tractor pulling at the Royal Show. He built his own tractor, called Nessie, and took it to agricultural shows across the country, including Keith Show, to gather interest.
Initially, the motorsport often ran in conjunction with these local shows, but it has since evolved into a standalone event. This shift has been beneficial in terms of health and safety, and track suitability at events. With over 40 members, the STPC has helped elevate tractor pulling to an international sport.
Despite being smaller in scale, the STPC doesn’t hold back in claiming its place on the podium, with many Scottish tractors reaching BTPA championships. These winners are then offered the opportunity to travel to the ETPC’s European championships, where two-day events rotate to different countries each year, with each competitor striving to become the European Champion.
Q. How are the tractors categorised into different groups?
A. Richard underlines: “Prior to each tractor competing, they are weighed according to their class, including the weight of the tractor, fluids such as coolant, oil, and fuel, plus the weight of the driver, all ensuring there are no breaches of rules.”
Super Farm
The Super Farm class is generally recognised as the entry-level category for participants, with the closest resemblance to a typical ‘farm’ model. Initially, these tractors were required to maintain their original gearbox and rear axle. However, current regulations now permit the use of component tractors—those equipped with a rear axle and gearbox sourced from trucks, which are both stronger and lighter.
Super Farm tractors are restricted to a maximum engine size of 6.6l. They are allowed to run only a single turbocharger of any size and must exclusively use diesel fuel. Engines under six litres have a maximum allowable RPM of 3200, while engines between six litres and the maximum size are capped at 3000 RPM. These tractors compete at a weight of 3500kg, with power outputs typically ranging between 500hp and 800hp.
Supersport
Supersport tractors adhere to the same regulations as the Super Farm class but with modifications to enhance performance. These tractors can have a maximum engine size of nine litres operating at 2700RPM, or 8.3l with an allowable RPM limit of 3200. They are approved to use only one turbocharger, regardless of size, and must run exclusively on diesel fuel. Competing at a weight of 4500kg,these tractors are estimated to produce up to 1800hp. Despite the relatively low RPM, they generate exceptionally high torque.
Limited Prostock
Limited Prostock tractors follow the same regulations as Super Farm tractors but with one key difference: there is no RPM limit. These tractors compete at a weight of 3500kg and are estimated to produce up to 1500hp.
Prostock tractors are limited to a maximum engine size of 8.3l. They are allowed to use a single turbocharger of any size and must run on diesel fuel only. There is no RPM limit in this class. These tractors, competing at 3500kg, are known to generate up to 2500hp.
Limited Superstock
Limited Superstock tractors are capped at a maximum engine displacement of 7.6l. While they share similarities with Prostock tractors, Limited Superstocks utilise spark ignition due to their use of methanol as fuel. There is no restriction on RPM, allowing these machines to reach engine speeds of over 7000 RPM. Competing at a weight of 3500kg, these tractors can generate power outputs ranging from 1500 to 2500hp.
Superstock
Superstock tractors are restricted to a maximum engine size of 10.65l. They are allowed to use up to four turbochargers, with a maximum of three pressure stages. These tractors can run on either diesel or methanol fuel, with no RPM limit. Competing at a weight of 3500kg, Diesel Superstocks typically generate around 150psi of boost pressure at 5000 RPM, while Methanol Superstocks generally operate with lower boost of 70-80 psi but at higher RPMs of over 7000. Power output for these machines ranges from approximately 1800 to 4500hp.
Modified
Modified tractors have the freedom to use any type of gearbox and rear axle. Generally, there are no restrictions on engine size, turbochargers, fuel type, or RPM limits. These tractors are versatile, allowing for engines to be added or removed to compete across different classes: Light Modified (2500-2700kg), Modified (3500-3700kg), and Heavy Modified (4000kg). Known for being the most spectacular in all of tractor pulling, some heavy modified tractors are capable of producing over 10,000hp.
A. Once a tractor has completed the 100m track, this is referred to as a ‘full pull.’ If more than one tractor completes the course, more weight is added to the drag. Competitors who move past 100m will compete in a pull-off, with the winner being the one who pulls the drag the farthest.
Q. Tell us a little more about the drag?
A. Without this, there would be no competition. The drag, known as a weight transfer drag and often referred to as the sledge, means that as it is pulled down the track, the weight is transferred (linked with gears to the drag’s wheels) from over the rear axles toward the front of the drag.
“In front of the rear wheels, instead of front wheels, there is a metal ‘skid’. The weight is ground-driven and moves forward via a gearbox and chains, increasing the resistance between the pan and the ground. The farther the tractor pulls the drag, the more difficult it gets. Initially, the rolling weight can vary from 14 to 24t, but once this weight is fully transferred off the wheels, it can achieve the equivalent of 100t.” said Graeme.
Q. What is the track made from?
A. “Typically topsoil, although we prefer to use clay as we find this gives a bit more grip. The rear tyres on some machines can end up turning at 90-100mph, so you want all the traction you can get.” explained Graeme.
Richard noted: “Most of Europe works on a sand track, although the Netherlands in particular use clay. You can also compete on topsoil, but this is less favoured than clay. The top events in the world all use a clay track.” The surface is very important as the tractors don’t utilise a lot of tyre tread; instead, it’s about a fine balance of torque, weight distribution, split brake compression, and tyre pressure.
Q. How is the sport funded?
A. Graeme describes: “A lot of them are a team of a few family members. My grandfather brought my family into the sport in the mid-80s, and my cousin Ross Forrest and I have since taken it on. Within the team, you’ll have your mechanics, two or three drivers, and everyone works together to get the tractor prepared.”
Tractors are transported to various events, typically loaded into an articulated lorry. Components such as roll cages and wheelie bars can be removed for transit. While many components were once manufactured in America, increasing interest in the sport has led to more production of these specialist parts in Europe.
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