Hamilton triathlete Scott Thorne has dominated the short history of the Big One - the Whaka 100 mountain-bike race - but this year there will be a new champion.

Thorne has won the first three years of the race in the Whakarewarewa Forest in Rotorua, which includes 100km of riding on a course that is mainly single track.

But he injured his knee in training in April and his recovery since surgery has been slow going.

"It is disappointing because I wanted to stack my name on the trophy year after year and carry on my dominance at that event," said Thorne, this year's Xterra New Zealand Champion.

"Winning that event means a lot to me and I will be hungrier for next year and back with a vengeance."

Thorne, a builder and a new father, had some good momentum from last year, when he won the Karapiro half-ironman, came second in the Rotorua half-ironman, second at the Xterra event in Malaysia and 13th in the Xterra world championships.

He holds the record at Whaka 100 4:43:42 set in 2008 - an average of about 22km/h.

"That was a good year, the pace was on right from the start and I will be gutted if someone breaks that record this year. But if they do it will give me something to aim for next year."

After living in Thorne's shadow for three years with two second places in the event Mark Leishman is hoping he can finally claim the title.

"Scott and I are good mates but I am tired of finishing second to him," said Leishman, 32, who also finished runner up to Thorne at the Xterra NZ Championship by 1m 1s.

"We feed off each other and that rivalry has taken us to a new level in our sports, but his absence this week has opened the door for me."

Leishman said his finest athletic achievements included "coming second in almost everything I have entered" and winning New Zealand's longest-running mountain bike event, the Karapoti Classic, last year.

"I have certainly got the capability, it is just a matter of getting it right on the day because small mistakes have big consequences in this race."

In previous years Leishman, who works for Bike New Zealand in Rotorua as the regional cycling development manager, and Thorne have raced The Big One as preparation for the Xterra World Championship.

But they are not going this year so Leishman admitted he was not as fit as he had been.

The leading riders reach serious speeds on the downhill sections, hitting about 40km/h on the single tracks and 70-80km/h on the open gravel road.

About 150 riders will contest the event, most of them from Australia.

Marcus Diprose of NDuro Event Ltd said the Australian market had been a focus in preparation for the fourth year of the event.

"We have deliberately targeted the Aussie market and built some good relationships with some event promoters over there and the numbers have increased markedly."

There is no other event like it in New Zealand. This year it has been modified to offer three courses, the 25km, 50km and 100km.

There are seven categories: sprockets (under 16) designed for young male and female riders (25km/50km only), junior (under 19), open (19-99), masters (35-44), vets (45-54), classics (55+) and single-speed.

"There are two races on," said Diprose. "There is the one against all the other competitors and also against yourself.

"For many doing the 100km race there is a huge amount of relief when it's all over as it is a long time to test your endurance on a bike."

The Whakarewarewa Forest race is particularly demanding because 75 per cent of it is single-track riding.

"It is up there with the most technical tracks in the country which makes it taxing," said Diprose.

"There are plenty of beautiful views along the way - whether or not you can enjoy them is another story as the views always involve big climbs."

Tomorrow a bunch of Aussies will find out what they are made of - and Leishman hopes to finally record a Whaka 100 win.

And, he says: "I look forward to when Scott is fit and healthy ... I'd love to beat him fair and square and enjoy that moment."

The Big One
* 100km of riding over a course that is predominantly single track

* Now in its third year the event has been slightly reformatted. Three courses are offered: 25km, 50km and 100km. A team's event has a 60km/40km split.