Buchanan will compete in the final of the downhill event at the mountain bike national series at Mt Buller on Sunday in her first race in her new discipline.

She is seeded third for the final behind Lisa Mathison and Claire Buchar.

The change of events comes five months after her BMX gold medal hopes were left in tatters at the London Olympics.

But Buchanan is determined to start fresh and wants to use her stint in mountain biking to make her fitter for her BMX hopes at the Rio Olympics in 2014.

While the BMX is a mad 30-second dash with seven other riders fighting to the finish line, the downhill is a solo race on a three-minute course.

Buchanan admits the increased speed, bigger jumps and added danger makes her nervous.

But the adrenaline junkie is excited by her new challenge.

''I've been off the downhill bike for four years now, but I know I've done the training work to get back up there,'' Buchanan said.

''I always set my goals pretty high and this is no different.

''In downhill you're on the track by yourself and racing against a time, which is what I like to do.

''But there's a bigger fear factor as well, the track is rougher and it takes more of a toll on your body so it's going to be interesting.''

Buchanan won a mountain bike world championship title in the four-cross event in 2009.

She was crowned BMX time trial world champion last year and was the fastest qualifier at the Olympics before disaster struck in the final.

The 22-year-old was devastated after failing to claim a medal, eventually finishing fifth after missing the start.

Her switch to mountain biking is designed to get rid of the pressure and refresh her mind before she begins to focus on Rio.

But after spending so long at the top of BMX, Buchanan will start at the bottom of the rankings in downhill as she attempts to win a spot at the world championships.

''I'm saying I want to go out and have fun, but I want to win as well. I'm not going out for a roll around,'' Buchanan said.

''It's been a bit hard to go back to the bottom after coming off the high of the Olympics … but it's a new goal, a new plan, a new discipline and new bikes.

''These first few rounds are about building my UCI points and ranking up and the top two from the national championships qualify for the world championships.

''That's my goal and I'd love to be on the downhill world championship team and then I'd love to win the world title.''

Buchanan's year got off to a perfect start when she became the first female in more than a decade to sign a sponsorship deal with cycling giants DK Bicycles.

She hopes to be in top form in time to perform at home when the national championships are held at Mt Stromlo from February 20-24.

The Erindale College graduate is not fazed by the extra pressure of racing in front of a home crowd and is confident she can capture another title.