The countdown to Australia's most prestigious annual race for standard passenger cars begins today when 59 entrants in the Super Cheap Auto 3-Hour Showroom Showdown take to the track for the first time at Mount Panorama, Bathurst.

Drivers of 23 different models representing 14 brands will take part in two pre-qualifying sessions that should provide a form guide for Saturday's enduro.

Rain yesterday over the 6.3 km mountain circuit and a forecast of more have cast doubt over early predictions that Holden's 400 horsepower Commodore GTS V8 sedans would be the cars to beat.

"I'll be happy if it rains - it will even up the David and Goliath contest with the Commodores," said ironman champion Grant Kenny, who has switched from surf to a Subaru for his crack at the mountain.

Kenny and teammate Scott Jacob are one of 12 combinations driving either Subaru Impreza WRXs or Mitsubishi Lancer Evo Vs which will enjoy the advantage of four-wheel drive if the track is wet.

While the Holden GTS Commodores of Ed Aitken/John Faulkner and Ross Dillon/Tony Scott chase outright victory, the driver pairing with the best recent Bathurst record will be battling at the other end of the field.

Steven Richards and Greg Murphy, who teamed last year to win the V8 Supercar Bathurst 1000, will contest the Showroom Showdown in a modest Holden Astra. The Astra is entered in the Bartercard Four-cylinder Touring class, one of five classes grouping cars in the GT Production category according to their similarity in the new-car market.

CAT Racing's John Bowe will swap his Ford Falcon V8 Supercar for a standard XR6 sedan, shared with class champion Daryl Coon. "It will be a challenge - it's a long time since I raced a car like this," Bowe said.

TIMETABLE: Thursday 10.30 am - Pre-qualifying, High Performance, Sports Touring classes (40 min.), 4.25 pm - Pre-qualifying, V8 Touring, Six-cylinder Touring, Bartercard Four-cylinder Touring (40 min.). Friday 3.40 pm - Qualifying (50 min.). Saturday 7.45 am - Warm-up (20 min.), 12.48 pm - Super Cheap Auto 3-Hour Showroom Showdown (180 min.).