Swapping his office garb for driving gear, businessman Vu Minh Hung readies for Vietnam's largest amateur off-road race, a mud-soaked adventure in the staid communist nation where professional auto sport is non-existent.

He was one of some 80 competitors at last weekend's race on a hilly track outside Hanoi, the ninth year of a competition that has ballooned in popularity among adrenalin junkies.

"There aren't many thrilling sports in Vietnam. We want to play thrilling sports but there are no opportunities for us. So this is exactly what I'm looking for," Hung told AFP, speaking after his leg of the race at the mud-slicked course. 

But the exhilaration comes with a steep price tag. 

Hung has spent $14,000 souping up his $32,000 Ford Ranger, now covered in colourful racing stickers, despite protests from his family. 

"My wife and relatives tried to stop me because they said it's a dangerous and costly hobby. But compared to other men's addictions I think my hobby is pretty nice," Hung said. 

The sport has taken off in Vietnam, where driving addicts like Hung say they can get a safe rush -- unlike drug users, alcoholics or gambling addicts.

But it's still far from mainstream in a country better known for its rowdy football fans than for gold-medal athletes.

Like all other road hobbies, off-road racing is not recognised as an official sport and therefore does not receive any government funding. 

Instead, drivers pay out of their own pockets to compete and bring their own 4x4s and SUVs to races. 

"We wish Vietnam could have an official sports car federation," said Khuat Viet Hung, deputy head of the national traffic safety committee.

Improving the sport's profile would help novice drivers to compete in neighbouring Malaysia or Thailand, where it is better established and receives more funding, according to race organiser Nguyen Manh Thang. 

He also hopes the race will sharpen car-driving skills in a country where motorbikes rule the roads, and where 30 people die daily in traffic accidents.

"Because traffic in Vietnam is chaotic, many people leave their homes and never return. We want safe driving in Vietnam," Thang said.

For competitor Pham Viet Thanh, competing for the second time, the race is about more than just skilful driving. 

"It's a passion. It's in my blood and brain. Anyone who wants to be manly should be involved in at least one sport and I consider this a sport," said the government employee, standing amid thousands of cheering fans at the race.

The secret to his success? An unlikely mistress. 

"This cute little girl is with me all the time," he says of his purple SUV. 

"When she's broken, I have to be gentle with her, fix her properly. I consider this car my second wife."