BOISE, Idaho (AP) - Whether commuter or competitor, cyclists dread the telltale clunk-and-spin of a dropped chain.

At minimum, it’s an inconvenience. For professional cyclists, however, one errant shift that throws their links into limbo can mean the difference between climbing the podium and also-ran status.

In this year’s Tour de France, at least one team, U.S.-based Garmin-Slipstream, will use a "chain catcher" first employed by former world champion Kristin Armstrong when she won the gold medal in the Beijing Olympics time trial.

In a sport where components like Armstrong’s "K-Edge Chain Catcher" are traditionally tested in pro cycling’s macho male peloton, this elegant innovation was put through the paces by a woman who pays attention to the tiniest details of bike racing.

"Everything you do to your bike adds up as free speed," the American told The Associated Press in mid-June from Minnesota, where she won the Nature Valley Grand Prix stage race. "It’s what you’re doing above and beyond what everyone else is doing that’s going to give you the five- to 10-second advantage you need to win."

She’s given one of the devices to Lance Armstrong, the seven-time Tour winner, and Levi Leipheimer, the bronze medalist in the Beijing Olympic men’s time trial. However, Philippe Maertens, a spokesman for their Astana team, said in an e-mail that it was on their bikes in a race" and won’t be used by them when the Tour begins on July 4 in Monaco.

Riders have long jury-rigged their own chain catchers. Others that clamp around the seat tube are available commercially. But Kristin Armstrong’s 10-gram aluminum version bolts onto the front derailleur, making it suitable for modern carbon-fiber racing bicycles with large, unconventionally shaped frame tubes.

A self-described aggressive shifter, she nearly lost the 2006 world championship time trial in Salzburg, Austria, when she dropped her chain.

Fearing a repeat in Beijing, Armstrong’s engineer husband, Joe Savola, sketched out the idea on a napkin. Boise-based AceCo Precision Manufacturing, whose main products include knives that chop McDonald’s French fries, refined it.

Her chain stayed on. She won by 24 seconds.

The U.S. Olympic team’s head mechanic, Nick Legan, also wrenches for the Garmin-Slipstream squad. After Armstrong’s victory, he ordered 45 chain catchers from AceCo before the pro team’s 258-kilometer (160-mile) Paris-Roubaix race in April over bone- and chain-jarring cobblestones.

Legan said it amounts to "an insurance policy."

British rider Bradley Wiggins used one during his second-place ride in the final stage of the Giro d’Italia in May. Now, the team’s nine-member Tour de France contingent will use them on all time trial bikes, and some road bikes.

"In the heat of the moment, with lactic acid boiling out of their ears, a racer will sometimes wait too long to shift, or shift over some cobbles," Legan told the AP from his home in Girona, Spain. "And that can spell catastrophe."

One of Garmin-Slipstream’s riders, Briton David Millar, knows that well.

Riding for a different team in the 2003 Tour, Millar was about to win the opening prologue when his chain fell off on the final corner. He lost by less than a second and cursed team officials in a well-publicized post-finish blowup. In this year’s Tour, his bikes will be outfitted with Armstrong’s chain catcher.

"We can’t win bike races for them, but we can lose them if we aren’t careful," Legan said. "The K-Edge takes one more issue out of the equation."