VANCOUVER, B.C. -- Having written a book a few years ago about the growth of urban cycling, I couldn't resist showing up here recently with my bicycle in hand for the annual Velo City conference that attracts bike advocates from around the world.

What I found was a bike movement perched on a kind of tipping point -- poised between making the kind of big gains in ridership we've seen in Portland and a political pushback that could dry up much of the federal funding for bicycle and pedestrian projects.

In a way that would have surprised me just five years ago, cycling has become a mainstream political force, both in U.S. cities and around the world. Officials in U.S. cities you don't normally associate with hordes of sweaty bike commuters -- such as Houston, Salt Lake City and Chattanooga, Tenn. -- are building bikeways and treating cycling as a serious form of urban transportation.

Mayors are getting competitive with each other, seeing bikes out on the street as a sign of urban vitality and public health, as well as a magnet to attract well-educated 20-somethings. One story, perhaps apocryphal, had it that Chicago's new mayor, the famously profane Rahm Emanuel, had made it clear using his favorite expletive that he was going to show Portland how to build a world-class bike network.

Within weeks of taking office, Emanuel installed a European-style cycle track -- which is physically separated from auto traffic -- on a major bike route leading out of downtown. While common for decades in the Netherlands and Denmark, cycle tracks have become newly fashionable in North American cities as a way to attract would-be riders who don't want to mix it up with auto traffic.

Vancouver itself has a couple of new cycle tracks through the middle of downtown. But at Velo City, the most remarkable sight was a fleet of 600 heavy-duty parked bikes provided for the use of attendees by PBSC Urban Solutions, a Canadian firm finding big money in the urban bike-share boom.

Starting from almost nothing a decade ago, about 450 cities in the world now boast a network of high-tech docking stations that dispense cycles for short-term rentals that essentially serve as an alternative to cabs, transit -- and, yes, cars -- for quick trips of a few miles or less. More than 40 U.S. cities either have bike-share systems or, like Portland, are in the process of setting one up.

The splashiest will go online this month in New York City, where Mayor Michael Bloomberg has cut a sponsorship deal with Citigroup to pony up $41 million to put 10,000 bikes in some 600 docking stations around the city. Bloomberg brags it won't cost taxpayers anything.

However, while the Velo City cyclists were celebrating their successes in city after city, they were also learning the political frailty of their movement. That same week, members of Congress put the finishing touches on a new federal transportation bill that could put a serious dent in funding for bicycle projects.

Simply put, the cyclists got right-hooked by the Tea Party, which pushed the Republican-led House of Representatives to demand an end to federal set-asides for bicycle and pedestrian projects. In the end, a compromise was reached, but cycling lobbyists fear they still face as much as a two-thirds cut in federal money for their projects -- which in the past have included such things as Portland's $30 million Eastbank Esplanade, built partly with federal money.

Andy Clarke, president of the League of American Bicyclists, said advocates had been abandoned even by some of their allies in the rush to agree to a bill that would keep road and bridge projects funded.

"It's now seen as a jobs bill," Clarke said, "and who's going to be against that? We're just unfortunate collateral damage as far as most people are concerned."

You see the political pushback beyond the halls of Congress. Cycling advocates love to celebrate Portland's success getting about 7 percent of its residents to commute by bike, the highest of any big city in the country. And it was achieved at bargain-basement rates: The cost of the city's entire bike network is far less than the $143 million spent rebuilding just one highway interchange, at Sylvan on U.S. 26.

But it's easy to find critics who think the city caters too much to cyclists, and one recent poll for The Oregonian suggested voters were wary of investing more in bikeways.

In New York, the city had to fend off a high-powered lawsuit from critics of a cycle track next to Prospect Park in Brooklyn. The new Toronto mayor erased the bike lanes on a prominent downtown street.

Urban cycling is now far beyond cute feature stories about plucky cyclists in a sea of automobiles. At Velo City, advocates were plausibly envisioning serious shifts in the way people get around cities. For example, Portland's bicycle master plan calls for 25 percent of trips to be made by bike by 2030, and it includes a wish list of $600 million in projects over 20 years.

Spending $30 million a year on a bikeway network is still relatively cheap compared to many transportation projects, whether it's the $3.1 billion Columbia River Crossing project or the $1.5 billion light-rail line to Milwaukie.

Still, it's upping the financial stakes, which can be a hard sell for voters who can't see themselves on a bike and have the kind of travel needs they can fulfill only by car.

I remember that kind of feeling. During Velo City, I had dinner one night with friends in Gastown, the city's touristy historic district. I then rode back to my hotel using Vancouver's new cycle tracks, exhilarated by the gentle summer breezes and the ease of moving after dark through downtown.

Then I remembered the last time I'd dined in Gastown, back in 1989 when I tagged along with a group of legislators studying the Canadian health care system. We made a similar journey back to our hotel, except by cab. And if you'd said then that 23 years later I'd easily do it by bike, I would have called you crazy.

Jeff Mapes is senior political reporter for The Oregonian and author of "Pedaling Revolution: How Cyclists are Changing American Cities."