McCombie (16), a pupil at King's High School, will compete in the under-19 downhill in Pietemaritzburg on August 30. The other Dunedin rider in the team is Raphael Kammlein-Cutler (18).
McCombie's brother, Dan (18), competed in the same event at the championships in Austria last year.
''My brother went last year and it's like a dream come true for me to go this year,'' he said.
''The experience of going overseas and competing with all the elite riders is awesome.''
Cycling has always been fun for McCombie who started competing in BMX aged 8.
He followed Dan into downhill mountain biking four years ago and has never looked back.
He admitted occasionally being scared when he started a downhill run.
''It gets the adrenaline flowing and it makes me go faster,'' he said.
The most dangerous part of a downhill course are the jumps. When a rider miscalculates, injuries occur.
But it does not worry McCombie - it is the part of the course he likes best.
He is totally focused on the job and is not thinking about falling off when he hurtles down the slopes.
''I'm completely focused on what lines are coming up and where I am going next. I like the feeling of adrenaline I get by going so quick.''
Most downhill mountain bikers get injuries and McCombie has had his share of mishaps.
His most serious injury was to break his left leg when he fell at the finish when winning the New Zealand under-15 title in 2010.
It was his first national title and the one he remembers the most.
''It was a good year for me,'' McCombie said.
''I won every race but one when I came in second.'McCombie won the under-17 title last year and was runner-up in the under-19 event this year.
A down side of his trip to the world championships in South Africa is that he has had to withdraw from the King's High School First XV.
He was on the wing last year and was named in the team again.
''But when I was named for the world championships I had to withdraw because I wanted to avoid injury,'' he said.
Another drawback of the trip to South Africa is the $6000 cost for airfares.
It will be the second trip overseas for Kammlein-Cutler who competed in Switzerland last year.
He is spending time in Europe preparing for the world championships and has competed in three races in Switzerland.
Kammlein-Cutler was the fourth junior home in the Swiss Cup, was 12th in the European Cup and was 38th in a world cup event.
He has been competing seriously in mountain biking for the past four years and finished fifth in the Southern series in New Zealand last summer.
He broke his hand in a training accident and missed the New Zealand series.
Kammlein-Cutler is coached by former women's world downhill champion Scarlett Hagen.
World championships
At a glance
Venue: Pietemaritzburg, South Africa.
Date: August 29-September 1.
Otago team members: Josh McCombie, Raphael Kammlein-Cutler (Dunedin), Alanna Columb, Kate Fluker (Queenstown).
