The cause of the crash in the Classic Adelaide rally which killed 60-year-old Gary Tierney and his co-driver David Carra, 43, remains under investigation.

But Classic Adelaide chairman David Edwards believes the fatal crash yesterday in the Adelaide Hills was a case of driver error.

Mr Tierney and Mr Carra, both from Melbourne, were killed when their 1974 Porsche 911RS skidded off a right-hand corner and struck a tree at Forreston, about 40 kilometres north-east of Adelaide.

Rally drivers and officials today held one minute's silence in honour of the duo, both experienced motor sport enthusiasts.

The corner where they died was "not anything tricky", Mr Edwards said.

"The road was clear and he lost his control of the car and couldn't get it back under control and hit a tree," Mr Edwards said on Friday.

"Something just went wrong.

"He was a very experienced driver and it wasn't any navigational problem, it was just a miscalculation I suppose.

"What happened was something in the car getting, as they say in driving, loose."

Mr Tierney had competed in five Classic Adelaide rallies and knew the dangers of motor sport, Mr Edwards said.

"It happens with all motor sport around the world, they know when they go in it," Mr Edwards said.

"They're competing, they're sportsmen and they like to achieve a win and therefore you can never predict it will never happen again."

Classic Adelaide media manager Chris Nixon said the fatal crash happened three kilometres into yesterday's 7.4km-long stage.

"It was over a crest and into a right-hand bend," he said.

"But there were no particular cautions on the drivers' charts for that (corner), a routine corner and many competitors would have taken it many times."

Mr Tierney had competed in rallies for more than a decade and was "a very experienced driver, well regarded by his colleagues and friends and rivals in motor sport," Mr Nixon said.

The rally continued as scheduled today.