During each of the years that the New Zealand Grand Prix had previously been held, 1954-1963, there were accompanying meetings held at various other New Zealand circuits. Wigram was used for the Lady Wigram Memorial Trophy race. Ohakea, on the outskirts of Palmerston North, was used in the early years for the Molesworth Trophy, along with Mairehau for the Hamilton Trophy race. A road race was also held in Dunedin, while in 1956 came Levin, also not far from Palmerston North, used for the first time, as was another road race held at Ryal Bush. In 1957 Invercargill hosted its first meeting at the newly finished Teretonga Park circuit and 1959 saw the introduction of the Waimate "round the houses" race.
All these races hinged around the NZ Grand Prix, and many saw the involvement of overseas drivers, who had come to NZ for the grand prix.
After the end of the 1962-3 New Zealand motor racing season, a great deal had been going on behind the scenes. This was preparation for the coming season, where, for the first time, the adoption of a restrictive formula was introduced. At the end of the previous season it was decided that the time had come when the controlling body of New Zealand motor sport, the Association of New Zealand Car Clubs, could introduce a measure of uniformity into the international race fields.
The result of the discussions between the association and international race promoters was the introduction of regulations limiting engine capacities of competing cars to a maximum of 2.5 litres, the banning of superchargers, and a requirement that all competing cars should run on 93 octane motor spirit, exactly the same as that offered motorists at their service stations. Previously international races had been conducted under Formula Libre conditions. In other words, drivers were able to bring to the starting grids cars of any engine capacity, supercharged or otherwise, and with absolute freedom of choice of fuel. Generally speaking, competitors with serious intentions favoured a Coventry Climax engine ranging in capacity from about 2.5 to 2.75 litres and operating on alcohol blended fuels.
The introduction of what was to become known as the Tasman Formula was greeted with some misgivings. In the first place it precluded the use of the lightweight American V8 engines which, in recent times, had proven extremely raceworthy when properly prepared. Thus a number of highly skilled American drivers had been excluded from the New Zealand racing scene. But, in New Zealand, those most concerned were the owners of the small Formula Junior cars into which had been fitted engines closely approaching 1.5 litres. Such cars could only produce a reasonably competitive power output when they are run on alcohol blended fuels. The force of the arguments of this group ultimately led to a compromise. The fuel regulation was amended to permit the use of aviation gasoline with a 100-130 octane range in place of 93 octane motor spirit.
Those who opposed the formula believed it would lead to a drop in lap and race average speeds. But the first few seasons proved that power output was not everything. Chassis design, weight, brakes and, perhaps most important of all, tyres, all play a part in paring down lap times and boosting speed averages. Comparing lap times from the 1963 Grand Prix, where 2.7 litre engines were used, to the 1964 Grand Prix, show that 1964 was faster, because cars had been specially built for the Tasman Series.
While the question of the Tasman Formula was being ironed out, negotiations which had been going on in rather nebulous fashion between the Association of New Zealand Car Clubs, the Confederation of Australian Motor Sport and representatives of the international promoters in both countries materialised into what became known as the Tasman Cup series of races. This was, in effect, a "minor league" World Racing Drivers' Championship. It had the effect of enhancing the prestige of motor racing in New Zealand and Australia and also stimulated keener competition between New Zealand and Australian drivers in races on both sides of the Tasman Sea.
The Australians had, in the past, tended to support only the New Zealand Grand Prix. Few of them had traveled further south for the Levin, Wigram and Teretonga meetings. On the other hand, a number of New Zealanders had campaigned actively and often to good effect in Australia. With the introduction of the Tasman Cup series, more Australian drivers were seen on New Zealand circuits.
For the Tasman Cup the points scoring system was similar to the then current system used for the world title. There were eight races, four in each country, although some years Australia only held three, and drivers counted points for three of the four races in each country but, in each case, one of those three races had to be the New Zealand Grand Prix at Pukekohe and the Australian Grand Prix at Sandown Park, Melbourne. Points were awarded on the basis of 9 for first, 6 for second, 4 for third, 3 for fourth, 2 for fifth and one for sixth place. To be sure of making the best score, drivers had to try and contest all races.
This eight-round series created greater public interest in motor racing in this part of the world, particularly as it was conducted during the European off-season.