The series is open to four door family saloon cars that have an overall length of no less than 4.2m. This removes the eligibility of small hot hatches or sports coupes, which could have an unfair advantage.
There is a required production run of at least 25,000 identical cars before any car can be homologated with the FIA, which was increased from the initial 2,500 units in 1995 in an attempt to remove the new breed of ‘homologation specials’ that were appearing, such as the Alfa Romeo 155 Silverstone.
All racecars must be built from a production body shell, with all panels being of the same shape and material as the homologated car. The shell must not have a sunroof (or it must have the opening sealed) and can be stripped of all unnecessary items such as soundproofing, non-essential brackets and external items such as mud flaps and number plate holders. The cars external lighting must still function correctly, and all must have at least one windscreen wiper.
Teams are allowed to strengthen the shell using seam welding to replace any existing spot welds and by adding a full roll-cage. This is designed not only to provide driver safety in the event of an accident, but it also helps stiffen the body to allow it to handle the extreme forces generated by the tyres and suspension.
Additional wheel clearance can be provided, by either changing the inner wheel arches to accommodate the wheels and tyres, or by cutting away a certain proportion of the wheel arch itself.
To equalise performance between the front, rear and four-wheel drive cars a series of minimum weights are imposed. These weights can be adjusted if one car is seen to be too dominant in the series. The technical scrutineers check these weights frequently and, since this is often done with the driver on board, an allowance of at least 80kg is made for the driver and his kit. This means additional ballast is required in cars with lightweight drivers to bring the weight up to the allowable limit.
These are the weight limits imposed from 1991 – 2000:
03-1991 – FWD 950kg RWD 1050kg 4X4 1050kg
07-1992 – FWD 950kg RWD 1025kg 4X4 1050kg
03-1993 – FWD 950kg RWD 1050kg 4X4 1050kg
03-1994 – FWD 975kg RWD 1025kg 4X4 1040kg
07-1995 – FWD 975kg RWD 1000kg 4X4 1040kg
05-1996 – FWD 975kg RWD 1000kg 4X4 1070kg
05-1997 – FWD 975kg RWD 1000kg 4X4 1040kg
03-1998 – FWD 975kg RWD 1000kg 4X4 Banned
For the 2000 championship, ‘success ballast’ was introduced which meant any driver achieving a podium finish was given an additional weight penalty. The top three finishers in each race would receive an additional 40kg, 30kg and 20kg, which had to be carried in the car at the following race meeting. A maximum of 40kg was given to any driver achieving a podium finish in both races.
A Super Touring racecar must be equipped with a normally aspirated two-litre engine with no more than 6 cylinders. Manufacturers are allowed to select any engine from its range, not necessarily from the homologated car, as long as over 2500 units have been produced in a 12-month period. The engine bore and stroke can be adjusted to meet the 2000cc limit if required, meaning a smaller or larger engine can be selected as a starting point. When fitted to the car, the engine must be located in the same relative position as in the production model (i.e. transverse or longitudinal) however it can be moved within the engine bay as long as no modifications to the engine bay are made.
To limit engine performance and development costs all engines are limited to 8500rpm, which until 1997 was controlled via a mandatory FIA approved electronic rev-limiter. From 1997, the rev-limiter became optional and a newly introduced ‘black-box’ data recorder became mandatory. The recorder enabled the scrutineers to record the engine revs over a longer period of time and thus check for any anomalies which a simple re-limiter would not pick-up.
In a similar way to F1 teams, the BTCC teams must also submit any Engine Control Units (ECU) to allow the scrutineers (or electronics specialists on behalf of the scrutineers) to check for illegal driver aids. This process was introduced in 1995 following rumours that some teams had introduced ‘software driven’ traction control within these units thus gaining an advantage.
Other restrictions on engine tuning and components are few, with the exception that the original cylinder block and head must be used, the number and position of cam-shafts must remain the same, and that the crankshaft and con-rods must be made of a ferrous material (i.e. no exotic titanium).
Each car can run a custom made exhaust, but the exit point must be at the rear of the car and the exhaust note must not exceed 110db at 6300rpm. All cars must run on a specific TOCA ‘control’ unleaded fuel and therefore must also be fitted with an FIA approved catalytic converter.
The rules allow for both front or rear wheel drive, with the racecar having to retain the same drive-train layout as the production car. Four-wheel drive cars were also permitted, but a rule change at the end of 1997 banned them from competing.
All cars can use purpose built racing gearboxes, which must have a maximum of 6 forward gears plus a mandatory reverse gear. No electronically assisted control of the clutch or gearboxes is allowed and the driver, via a mechanical linkage, must make all gear selections.
Sequential gearboxes are allowed, which are smaller and lighter than traditional H pattern units, and also have the added advantage of allowing the engine to be mounted lower in the car.
A mechanical limited slip differential can be situated between the two driven wheels, but no electronic anti slip devices are allowed.
As with the other significant components on the racecar, the suspension type and configuration must remain true to the original specification found on the production vehicle. This being said, the teams have a lot of scope to enhance the suspension and improve the handing of the car via the use of pure racing components.
Although the suspension type must remain the same, the positioning of the components is variable within certain tolerances specified within the rules. Items such as springs must also remain the same type, but additional springs can be added so long as they can be fitted without significant modification to the suspension configuration. The same applies to shock absorbers, with the rules requiring that the same number of dampers are fitted, but can be replaced by combination spring/damper units if desired.
No ‘active’ suspension mechanisms were allowed, but the drivers are allowed the ability to adjust the front and rear anti-roll bars from within the cockpit during the race.
The only other restriction on the suspension wa that no composite material could be used within any of the suspension components.
Wheels and Tyres
This is another area where the rules have been designed to try and equalise performance between the various cars participating. This is achieved by restricting the tyre width to 9 inches and the overall diameter to 650mm, thus limiting the level of grip available to all cars.
Another restriction is in the number of tyres available to each car for qualifying and racing. When the rules were initially written, a maximum of six slick un-treaded tyres per car were allowed for each race event (or wet tyres if it was declared a wet race). This meant that two of the tyres used for qualifying would have to be used (and last) the race itself, thus limiting the use of sticky qualifying tyres. At the newly introduced ‘double’ and ‘twin’ race meetings, the teams were allowed to use a completely new set of tyres for the second race.
In 1995, all rounds (excluding the British GP support race) became two race events, with a qualifying session for each race. Tyres were now restricted to 6 slicks per qualifying session and associated race.
Then in 1998, the two races became a short ‘sprint’ race followed by a longer ‘feature’ race. Although the six-tyre rule continued to apply to the sprint race, the qualifying was now reduced to a one-shot lap per driver to decide grid position. The longer feature race now required a mandatory pit stop and tyre change; however only two tyres could be changed per car, and these could be new tyres.
The physical wheel diameter is only restricted in so far as the complete wheel and tyre unit must fit within the proscribed tyre size rules, and that the wheel itself must not be made of a composite material.
Initially, the use of tyre warmers was not permitted, but this rule also changed in 1998 to allow the teams to use them in the pits but not on the grid before the race.
The use of aerodynamics is one area where the rules have changed significantly since their first drafting in 1989. Following attempts by some manufacturers to use loopholes in the rules to gain an unfair advantage over the remainder of the field, the FIA changed the rules in attempt to re-introduce a level playing field.
The original rules kept the racecars silhouette identical to that of the production model by stipulating that any aerodynamic device used on the racecar must also appear on the homologated car. This not only gave the cars an easily recognisable ‘showroom’ look, but also limited the aerodynamics of the cars to produce closer racing. However, in 1995 the rules were changed and all teams were allowed to develop and use non-production aerodynamic kits on their racecars. Each aerodynamic package can consist of a front spoiler and splitter plus a rear wing.
The front dam must not project further forward than the original bodywork and must also be at least 45mm off the ground. Also, no part of the car should touch the ground when both tyres on one side of the car are deflated.
The rear wing must fit within an imaginary box with a cross-section of 150mm x 150mm and must not be adjustable. It must be fitted no nearer than 100mm from the rear of the car and should be no wider that the car itself, to the extent that it must not be visible when viewed from the front of the car.
All aerodynamic packages must be registered with the FIA before the beginning of the season and then cannot be changed during that season.
The limitations on brakes are few, and mainly concern the use of composite materials within the disk and calliper mechanism. All disks must be made of a ferrous material but there is no restriction on their size other than the limits imposed by the size of the wheel within which they must fit. The callipers must be made from aluminium materials, but the number of callipers per wheel is not restricted neither is the number of pads per calliper.
The brake pads themselves can be made of any material and can only be cooled by air ducted from the front spoiler or from the rear of the car. The callipers can be cooled via a closed loop liquid system with the fluid reservoir being carried on-board the car.
Although seen initially on a number of cars in 1992, anti-lock brakes were quickly banned and no form of pneumatic, electric or electronic brake adjustment is allowed. The exception is the cockpit mounted brake balance mechanism, which can be adjusted manually by the driver during the race.
Driver safety is one of the most crucial features of a Super Touring car. Since their introduction, the rules have changed often to ensure that the drivers are not take unnecessary risks when racing.
The most obvious safety device is the roll-cage, which also acts as a second chassis for the cars. The design of these cages has improved quite dramatically over recent times with more focus being given to the area containing the driver. The drivers seat has been moved more towards the centre of the car and is surrounded by the roll cage and new door bars. Additional energy-absorbing carbon fibre composite panelling must be fitted to the doors and the roll cage and the seating must provide lateral protection for the drivers’ head in the event of a side impact. The usual 6-point safety harness is required to keep the driver safely in his seat.
Window glass must be exchanged for lightweight polycarbonate shatterproof plastic, with the drivers widow having to be fitted with a safety net. New rules regarding the drivers’ ability to exit the car quickly have also seen the introduction of Formula 1 style removable steering wheels.
All cars must be fitted with a fire extinguisher that can be operated by the driver or by a marshal from outside the car. Engine cutout switches are also required inside and outside the car.
All drivers must wear FIA approved crash helmets and suits made from flame-resistant material, with underwear, socks, gloves and a balaclava-type helmet lining of a similar material.