E-bikes are the fastest expanding sector in the bike market. (Mel Melcon/LA Times via Getty )

It doesn't take long to hear the hum in downtown Walnut Creek: the gentle purr of an electric bike. In the 90 degree June heat, riders zip past diners on Locust Street, dart across crosswalks two-to-a-bike, and cruise in the shade of the Contra Costa Canal Trail.

Some of the e-bikes are sleek multi-thousand-dollar models. Others are amateur builds, with motors and wiring attached to the bike's frame with duct tape. But this afternoon's crop of riders all have one thing in common: not one looks over 18, and some far younger.

E-bikes are the fastest expanding sector in the bike market - responsible for 63% of the growth in dollar sales of all bicycles, according to one recent study. They've become a mainstay in city bike lanes for commuters and a car alternative for families with young children.

According to Zac Crenshaw, a bike sales expert at Mike's Bikes in downtown Walnut Creek, older customers have been steady e-bike consumers for years because the electric assist eases the strain of pedaling, and athletes like the bikes for long rides where they want to keep their heart rate low. But now, Crenshaw says kids and teens are making up a growing share of e-bike consumers. The demographic shift toward younger riders has raised concerns of dangerous behavior on the roads across Bay Area communities that weigh heavily against the vehicles' benefits.

The Electric Bike Center, in Walnut Creek, will not service any bikes with at-home modifications like custom batteries or controllers. (Summer Maxwell/SFGATE)

Crenshaw estimates he's been passed by kids traveling 30 to 40 mph on e-bikes. "The number of times that I've seen a 12-year-old kid fly down the bike path, I mean, I'm breaking the speed limit myself, and they're going significantly faster than me," he said.

Across town, at the Electric Bike Center, e-bike specialist and salesman John Dizon now estimates that 30% of the store's e-bike sales come from parents buying the machines for their children.

E-bikes are categorized nationwide into three tiers. Class 1 and Class 2 e-bikes do not provide motor assistance over 20 mph, and Class 3 tops out at 28 mph. On Class 1 and 3 bikes, riders must pedal to receive the motor assist; on Class 2 bikes they can activate it with a throttle. There is no license of any kind required to operate an e-bike.

In California, riders must be at least 16 to operate a Class 3 bike, but certain communities have gone further to impose restrictions. Effective Tuesday, Marin will become the first California county to implement an age restriction on Class 2 e-bikes by banning riders under 16.

A modified e-bike seen at Broadway Plaza in Walnut Creek, Calif. (Summer Maxwell/SFGATE)

But buyers can also modify their e-bikes at home using parts purchased from Amazon, eBay or overseas sellers to replace motors or controllers to make the bikes go faster than manufacturers intended. On a recent trip to Walnut Creek, one modified electric blue e-bike parked at Broadway Plaza appeared to have electrical wires held to the frame with zip ties and duct tape and a motor mounted above the rear wheel with rusted bolts.

How strictly e-bike makers stick to the classification guidelines has also been called into question. In December, a Fairfax mom filed a class action lawsuit against Irvine-based e-bike manufacturer Super73 after buying an e-bike for her son's 12th birthday.

The suit alleges that the company's Class 2 e-bikes provide motor assistance at speeds well above the legal limit, thanks to a Super73 app that users can use to prompt their bikes into an "unlimited" or "off-road" mode and reach 38 mph - speeds that would require the bikes to be classified as motor vehicles and riders to have a driver's license. The litigation is ongoing, and Super73 did not return a request for comment by publication time.

Super73 also issued a recall in February for two models regarding a loose part that could result in brake failure. The affected units were sold between April and September of 2024.

In California, riders must be at least 16 to operate a Class 3 bike, but certain communities have gone further to impose restrictions. (Mel Melcon/LA Times via Getty )

Dizon said he had to turn away a minor who brought their Super73 bike - modified with a custom controller and battery to boost the bike's speed - into the store for maintenance. Most bike retailers won't service e-bikes with motor components they don't sell to mitigate liability risk.

Data from Marin County Health and Human Services shows that e-bikes have a lower accident rate for all age groups over 16 compared to conventional bikes, but result in a higher accident rate among riders between ages 10 and 15. (Contra Costa County does not publish equivalent statistics.)

Last month, a 13-year-old riding an e-bike was seriously injured after crashing into a truck in Millbrae. In May, a Stanford student was fatally struck by the driver of a car while riding an e-bike on campus.

In suburban communities like Walnut Creek, the appeal of the e-bike to young riders is obvious. Mike's Bikes sells models from a steep $12,000 down to about $1,500 - more affordable than a car and available to those who aren't yet old enough for a driver's license.

The Electric Bike Center in Walnut Creek, Calif. (Summer Maxwell/SFGATE)

But according to Dizon, e-bikes come with unique risks that parents should be aware of before buying one for their child, especially how quickly they can whizz down roadways.

"Vehicles aren't aware that bikes can go certain speeds," Dizon said. "If someone pulls out of a driveway, they can't gauge the speed the bike is going. That's a potential risk of you getting hit."

That's exactly what started to worry Mary Naegeli, who first noticed the uptick in young e-bike users when she moved closer to Foothill Middle School in Walnut Creek. Backing out of her driveway, she learned to watch for kids on their way to school coming down the wrong side of the road.

Naegeli is an e-biker too - but asked the Walnut Creek City Council to step in last month after being nearly hit on her bike by teens riding on the wrong side of the road and witnessing three young bikers riding dangerously close to a woman as she crossed Ignancio Boulevard.

"I absolutely love the fact that kids are riding their bikes to school. That is not the issue," she told the city council in May. "But what is alarming to me now is the way that they are driving motorized vehicles, e-bikes and scooters, way too fast."

E-bikes don't require any form of registration or licensing for riders. (Mel Melcon/LA Times via Getty )

Walnut Creek Mayor Cindy Darling told SFGATE she saw the need for action herself this school year. "I watched the kids heading to both the middle school and the elementary school, and I realized they probably need a little bit of education to help them operate those vehicles safely," she said.

Since the bikes don't require any form of registration or licensing for riders, much of the issue could boil down to the fact that many e-bike riders have never taken any form of driver's education or other courses to learn the rules of the road, and parents aren't aware of what the e-bikes they purchase for their children are capable of.

"It's a problem, when the kid's parents buy it and they don't know what they're getting into," Dizon said. He also thinks that the few teens who are breaking the rules are negatively affecting the wider e-bike community.

"They're ruining it for everybody else," Dizon said.

For now, it appears Walnut Creek won't be following Marin's lead by enacting stricter rules around e-bikes. Darling explained the city's approach is focused on working with local schools and the Walnut Creek Police Department to educate students and parents about road safety.

"This is a great form of transportation for kids if used properly, and that requires parents working with their children to understand what the requirements are," she said.

Kids and teens are making up a growing share of e-bike consumers. (Mel Melcon/LA Times via Getty )

Dizon agrees that naivete and a lack of research by consumers is the biggest hurdle to safer e-biking. When families come into his store to purchase an e-bike, he says the bike most kids point to when they walk in is the Eunorau R1: an electric dirt bike that can travel up to 55 mph and isn't street legal. Dizon said he's seen several kids as young as 12 on the bikes.

"If it's too much of a bike for the kid, we'll tell the parents it's not a good idea," Dizon said. But he also can't stop buyers if they want to proceed even after being informed of the risks.

As part of the education initiative, the Walnut Creek Police Department is hosting a Bike Rodeo on Saturday, July 12, at Civic Park for families to learn about e-bike safety and register their bikes.

"There will always be kids who know the rules and break them, and they're the knuckleheads," Naegeli said. "But I think that it's basically an education issue."

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