French defending Olympic champion Julien Absalon is the strong favourite to win gold in the men's mountain bike race on Saturday though a muddy course may lead to upsets in both the men's and women's race.
The difficult Laoshan circuit is expected to test even the best mountain bikers and heavy rains on Thursday could make a mess of the course.
Fifty men and 30 women will race a series of laps on a 4.5km loop that includes banked curves, drops, rocks and climbing sections through heavy brush and woods. The women's cross-country final is on Friday and the men's on Saturday.
Absalon, winner of four consecutive world championships and 13 career World Cup rounds, is a powerful climber with strong descending skills that should serve him well in Beijing.
But Switzerland's Christoph Sauser, a strong climber and good technical rider, could present a tough challenge along with his teammate Florian Vogel.
Jose Antonio Hermida of Spain, the silver medallist in Athens, said changes to the course since last year's test event had made it much more difficult.
‘We were complaining last year that it wasn't hard enough, now we're finding ourselves in a situation that it might be too hard,’ Hermida said. ‘They've put some big stones in the wooded section ... It's a beautiful course, a hard course.’
Hermida's team mate, world champion Margarita Fullana, is one of the favourites on the women's side.
She will try to stop Norway's Gunn Rita Dahle Flesjaa from repeating her 2004 gold performance. Dahle Flesjaa struggled with health problems recently but appears to be returning to form.
