Ashley Giles rides a bike on a trail on Raccoon Mountain.

The dog days of summer have forced some changes to this weekend's mountain bike race, which is part of a race series run by the Chattanooga chapter of the Southern Off-Road Bicycle Association.

SORBA had planned to run a two-day event this weekend at Raccoon Mountain with an endurance time trial as well as the Super-D downhill race, but lower-than-expected registration numbers forced Team SORBA race director Michael Long to cut the race to one day for the Super D on Saturday.

Long said the low turnout was surprising after solid numbers of participants at the first two races of the series, including 133 racers in April for the Night Shift race at Enterprise South.

"We were getting really low registration numbers," he said. "Lower than we should have been, so we had to protect the club. The club could not afford to lose money, so we had to make a choice."

"We got a little bit of backlash, but I think moving forward it's going to encourage people to pre-register."

For anyone who still wants to participate in Saturday's Super-D, online registration remains open and riders can register until 11 p.m. Friday at teamsorbachattanooga.squarespace.com/raccoon-mountain.

Long said that despite the setback, Super-D registration has been fairly solid lately, with riders from across the region coming to race on the newest trail extensions at Raccoon Mountain on the 8 1/2-mile Live Wire extension. The 5 1/2-mile race will be the longest super-downhill race in the Southeast with a elevation drop of 1,200 feet.

Riders will leave the start at intervals of 30 seconds to a minute, depending on how many racers are participating, and Long said the course will be a challenge.

"It's going to be tough," he said. "You're not going to be able to show up with just a downhill bike and dominate. You've got to have some pedaling skills and you've got to have some bike-handling skills to win this race."

The SORBA Chattanooga race series will conclude Oct. 11 at the Lula Lake Land Trust 5-Points 50, a 50-mile race on Lookout Mountain that will be held the week of the RiverRocks outdoor sports festival.

Contact Jim Tanner at jtanner@timesfreepress.com or 423-757-6478. Follow him at twitter.com/JFTanner.