Mountain bikers and marathon runners will be crawling over the sharp volcanic rock of Rangitoto this month.

It is the first time bikers have been allowed to race on the Auckland landmark.

Organisers hope the new event, called "The Dual", will be embraced as part of the Auckland sporting calendar in the same way the Coast to Coast multisport race is in South Island sporting culture.

And like the Coast to Coast, The Dual's founders hope to bring together a unique landscape, concern for the environment and tough sporting challenges.

The Dual name refers to the two islands the event will be raced on - Rangitoto and its lesser known twin, Motutapu.

Three races are being run as part of the first Dual on March 28 - a 50km mountain bike ride, a full marathon (42.2km) and a half marathon. Teams of two can also run the marathon.

Total Sport is the force behind The Dual. The sports management company has contracts to run events such as the Auckland Marathon, but also puts on its own races, such as the North Shore Coastal Challenge, in which competitors run the length of the North Shore's beaches, from Whangaparaoa to Devonport.

Company founder Aaron Carter said it had taken nearly two years of negotiations with Department of Conservation and the Motutapu Restoration Trust to gain approval for the event.

By happy coincidence, the Motutapu trust was also looking for ways to get more people to the island and raise money for its work there.

Motutapu is being transformed by the trust, which hopes The Dual will introduce the island to thousands of people who have never thought of visiting it.

It has been planting native trees, killing weeds and restoring historic sites on the island for 15 years.

The fear of coming into sudden contact with the sharp volcanic rock hasn't put people off - more than 1320 entrants will head to the island on March 28.