As Andrew Farmer explained why he came to Sunday’s Tour of Lawrence bicycle race downtown, the sound of scraping metal suddenly arose from the corner of Eighth and Massachusetts streets.

About eight riders had just crashed, and it was only the first lap of this race.

Just another part of the excitement that is criterium racing.

A criterium is a high-speed road bike race that occurs on a short, closed course. The Lawrence course covered a mile and took racers along Massachusetts, New Hampshire and Vermont streets. The length of the race increases with the skill level of the racers — the novice categories raced for 25 minutes while Sunday night’s professional race lasted 75 minutes.

Farmer said he was impressed with the racers’ skills.

“It’s fun to see them come around the corner at insane speeds,” he said.

Jose Alcala, whose SRAM Neutral Support team helps racers with equipment problems, said criteriums are a great spectator sport. The racing is exciting, and riders pass by every few minutes, he said.

Alcala said the racers need great bike-handling abilities to navigate the technical courses. He said efficiency is key because riders need as much energy as possible for the final laps of the race, which generally end in a mass sprint.

However, riders do manage to break away from the main group, also known as the peloton. Several times during the race, organizers will announce “primes laps,” which offer a prize to the first rider across the line. Racing intensifies during these laps and gives racers a chance to escape.

Alcala, who travels to bike races across the country, said Lawrence’s eight-turn course is one of the best he’s seen.

Tour of Lawrence activities began Sunday morning with the Mass Street Mile run and the children’s bike race.

Heather Harper, of Olathe, participated in the run while her children, Connor, 9, and Lauren, 7, rode in the children’s race. Her husband competed in one of the bike races later that day.

“We just made it a family affair,” she said.

More people arrived downtown as the racing began at noon, but rain pushed them under storefront canopies about 1:30 p.m. The weather cleared a few hours later, and fans gathered at prime viewing spots as the higher-skilled racers took the course.

However, wet roads were a catalyst for crashes. Racers who took corners too fast were given a harsh lesson in gravity and traction.

“The rain adds a whole new element to racing,” Alcala said.

The downtown course was as great for the fans as it was for the racers. Mat Stephens, who participated in the pro race, said criteriums always have the biggest crowds.

“The thrill of the crowd makes you push harder,” said Stephens, who is from Dallas and travels the country with his Elbowz Racing team.

Although he said he loved Lawrence’s energy, he said he wished the race took place at night like the Athens Twilight Criterium in Athens, Ga. He said the race attracts even bigger crowds as cycling fans and bar patrons alike lined the college town’s course to cheer on racers.