Anthony Effinger / Bloomberg News

PORTLAND — In other cities, welders pull up to a job in oversize pickup trucks rattling with tools and pressurized tanks of gas. In Portland, at least one arrives by bicycle, towing his gear in a two-wheeled trailer.

Mike Cobb pedals around town fixing iron handrailings and welding kettle stands for coffee-roasting companies. He built the frame on one of his six bikes himself and souped up his trailer with racing wheels and high-pressure wheelchair tires.

“I do a pretty good job of avoiding cars,” Cobb, 42, said one morning outside his garage. There's no automobile inside. He hasn't owned one since 1995 and only rarely catches rides with friends, he said.

Portland is No. 1 for bike commuting in the United States, according to 2010 Census figures for cities with more than 250,000 workers. A study of the data by Bloomberg Rankings shows that bicycles carry 5.4 percent of workers in Portland, ahead of second-place San Francisco, at 3 percent. Seattle is third at 2.8 percent, and Washington, D.C., is fourth, with 2.2 percent.

Portland is also the fastest-growing city for bike commuting, up 1.3 percentage points since 2006. San Francisco grew 0.7 percentage points in the same period.

Riders such as Cobb are pushing the limits on how far they can go and how much they can carry. Portlanders haul kids and groceries on specialized cargo bikes. They gather with trailers to move friends by bike, barn-raising style, then post the video online. They play polo on bikes and, at least once a year, thousands assemble for an evening of riding naked.

An eco-friendly industry is growing amid the mania. Portland-based Metrofiets builds bikes with large cargo bays up front. Trailhead Coffee Roasters makes deliveries with one. Splendid Cycles is the largest North American dealer of a line of slender cargo bikes from Copenhagen, Denmark, said Joel Grover, the shop owner.

At least two dozen companies build bikes by hand in Portland. Sweetpea Bicycles caters to women, with one model called the “Little Black Dress.” Sacha White's Vanilla Bicycles isn't taking new orders for its custom models until it works off a backlog that once stretched six years.

A 2008 study found Portland's cycling-related industry brought $90 million a year into its economy. Those businesses keep money from leaving town, Mayor Sam Adams said.

“Every dollar spent on a car in Portland is a dollar that leaves the city,” Adams said. “We don't make cars, we don't have oil wells, and we don't have a major car insurer headquartered here.”

One reason for cycling's popularity is Portland's temperate climate, said Ray Thomas, an attorney who twice a week for the past 20 years has ridden in the lunchtime “Lawyers Ride” into the hills west of town.

“It's mild and kind of drippy,” Thomas said.

The region's notorious rain comes mostly as drizzle. Snow sticks on the streets only about four days a year, according to the National Weather Service, and summer days rarely breach 100 degrees Fahrenheit.

Political leaders have also pushed biking. Bud Clark, mayor of Portland from 1985 to 1992, biked to City Hall most days and encouraged others to follow his lead.

Rep. Earl Blumenauer, a Democrat, cycles to his office on Capitol Hill in Washington. For years, he fought for the passage of 2008's Bicycle Commuter Act, which permits companies to offer bike-commuting workers a monthly $20 fringe benefit.

Portland has had a bike master plan since 1973 and has 318 miles of bike lanes, paths and greenways, or residential streets where cyclists are given priority. The latest plan calls for a quarter of all trips to be made by bicycle by 2030.

Local brewer Christian Ettinger opened the Hopworks BikeBar on one of Portland's busiest cycling routes in June. Two stationary exercise bikes generate electricity to help power the business.

“People can turn their valuable beer calories into electricity,” said Ettinger, 38.

For $10, customers can get a bottle of beer that fits in a water-bottle holder on their cycle, and a sandwich wrapped tight to fit in another.

On a bigger scale, Portland-based Alta Bicycle Share won the contract to operate New York City's 10,000-bike rental program, beginning in July, which Mayor Michael Bloomberg said will be the largest in the nation.

Biking to work

Portland is the cycling capital of major U.S. cities, with more than 5 percent of its workers biking to their jobs. Other ranking cities:

1. Portland

2. San Francisco

3. Seattle

4. Washington

5. Denver

6. Philadelphia

7. Boston

8. Albuquerque, N.M.

9. Chicago

10. Austin

— Bloomberg rankings used data from the U.S. Census to identify cities with more than 250,000 workers in 2010.