JEFFERSON — The fat-bike phenomenon continues to win fans. When a fat-bike seminar was offered at Hidden Valley Nature Center a few weeks ago, many rode in the world of wide tires for the first time and came away converts.

“It’s like a car,” said 11-year-old mountain biker Eoin O’Mahoney of Whitefield, who led a youth ride at the mountain-bike event at the nature center.

Joe Arsenault of Phippsburg had ridden fat bikes before. But the one he road on this ride, with tires an inch wider than the classic fat bike tread – about 4.5 inches – was a new experience.

“There’s more traction,” Arsenault said.

And Nature Center co-founder Tracy Moskovitz enjoyed the smooth, stable ride that could cut through leaves with little notice of the stones and roots underneath.

“It feels more stable,” Moskovitz agreed.

Fat bikes are mountain bikes with wide tires that provide a smooth ride on uneven surfaces like snow and sand. While traditional mountain bikes have tires about 2.2 inches wide, fat-bike tires can be twice that.

The genesis of the fat bike is believed to have come from the first Iditabike 200-mile challenge race in Alaska in 1987, a grueling race that follows dog-sled trails in wintertime backcountry.

A decade later, fat bikes were sold at trade shows, according to the Adventure Cycling Association in Missoula, Montana. Then in 2005, the first Surly Pugsley helped to spread visibility of the fat bike when widespread marketing of the monster bike helped sales take off.

Since then, the fat bike remains the fastest growing segment of the bicycle market, according to Adventure Cycling. Today, the bikes can cost $2,000 to $3,000, but others are available for around $1,000.

Hidden Valley Nature Center, with the help of the Maine Winter Sports Center, brought dozens of mountain bikes to the nature center’s 30 miles of multi-use trails two weeks ago. And Bath Cycle and Ski provided about 10 fat bikes that were rented out in the first hour. The demo day opened novices’ eyes to the wonder of wide tires.

At Bath Cycle and Ski, Forrest Carver has been designing and selling his own brand of fat bikes, which is the store’s “house brand.”

“December used to be our slowest month. It used to be the offseason. The past three years, December has been the best month,” Carver said, referring to the growing sale of fat bikes.

Riding in on his 20-year-old Trek mountain bike, Jim Hazel was eager to try a fat bike at the mountain-bike open house. Like every other first-time fat-bike rider, Hazel was in disbelief over the smooth, easy ride.

“I saw this in the paper and thought, I’ve found a home,” said Hazel, 63. “My first thought when I tried it was, am I going to go down when I do a slow turn? But I was in control. I felt a lot safer.”

After moving to Bristol three weeks ago after retiring from the police department in Marblehead, Massachusetts, Hazel said he’s been looking for new adventures. Now the owner of 100-acre lot, Hazel said a fat bike would help him explore his land a lot better.

A former bicycle patrol cop, Hazel has had a passion for mountain bikes for 30 years. He had photos taken of him on a fat bike to send to his friends at the Marblehead Police Department.

“We were one of the first uniformed departments to patrol on bicycles in 1984,” said Hazel, 63, proudly.

O’Mahoney has mountain biked for three years and rides the trails at Hidden Valley. He said riding a fat bike was like a different sport.

“It’s very stable,” the youth said. “You can ride over anything and hardly feel it.”

Others agreed, fat bikes amount to mountain biking made easy.

Ewa Prokopiuk of Jefferson enjoys hiking at the nature center. She was game to try a sport she knew nothing about.

“I’m not a biker. But I felt comfortable, like I wasn’t afraid of the bumps and the trails,” said Prokopiuk, 53. “It’s fun but it’s hard. I just hiked the Grand Canyon and this is completely different muscles. I would rent one again.”