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from the I've-never-had-functioning-brakes,-I-don't-oil-my-chain-and-my-derailleur's-out-of-adjustment dept.
Brakes that are too effective have led Lyft to remove thousands of its electric pedal-assist bicycles from New York City (Citi Bike), San Francisco (Ford GoBike), and Washington, D.C. (Capital Bikeshare):
A month ago, Jordan Wyckoff was riding an electric Citi Bike to work in Brooklyn when he slammed on the brakes to avoid a minivan that swerved in the bike lane. But when he hit the brakes, the front wheel locked up, sending Mr. Wyckoff over the front of the handlebars and onto the pavement.
The same thing happened to Dominik Glodzik when he tried to brake before a stop sign in Astoria, Queens about two months ago.
William Turton flipped over the front of an electric Citi Bike while trying to brake before an intersection on Bedford Avenue in Brooklyn.
In recent months, dozens of riders have reported injuries while riding electric Citi Bikes, prompting the company on Sunday to pull all of the approximately 1,000 electric bicycles from New York City's streets amid safety concerns about the brakes. Lyft, which owns Citi Bike, took similar precautions with its other bike-sharing services in Washington and San Francisco.
Motivate, a subsidiary of Lyft since 2018, operates bicycle sharing systems in several cities.
Previously: Uber May Try to Buy Citi Bike Parent Company Motivate
Lyft Acquires America's Largest Bike-Sharing Company, Motivate
Related: New Electric Bikes, Scooters, and Dockless Bicycles Hitting U.S. Streets
Uber Buys Electric Bicycle-Sharing Startup JUMP Bikes
(Score: 1) by Coward, Anonymous on Tuesday April 16 2019, @11:35PM (1 child)
Sorry to reply to my own post, and for blaming the victims, but this story [washingtonpost.com] has more details. I can easily imagine brake levers with the wrong leverage ratio having being installed, which could explain the handling problems.
As the late Sheldon Brown wrote [sheldonbrown.com] when discussing brake lever mismatch:
(Score: 0) by Anonymous Coward on Wednesday April 17 2019, @02:52AM
Thanks for digging out that WP article. The initial point I was trying to make is that these bikes don't use a "normal" (for USA) front brake. Drum brakes are just that much different than rim brakes (or disks) and have their own set of strengths and weaknesses.
If the WP article is correct, it's possible that the brakes were combined with the wrong levers as you suggest. Or they could have been improperly assembled. Typically these have two internal "shoes", one leading and one trailing. The leading shoe is "self energizing", braking force tends to increase the contact force between shoe and drum due to the internal geometry. If this shoe doesn't have a fairly strong return spring, or if it isn't well controlled (tight fitting pivot), it could jam and lock the brake with very little lever force by the rider.
In the era before disk brakes were common on cars, drum brakes and self energizing (or "servo) was studied at length, with the goal of reducing brake pedal force for heavy cars. For example, brakes were made with additional linkage internally and two (or more) leading shoes. Here are pictures of three common types, https://www.quora.com/What-are-the-3-types-of-drum-brakes [quora.com] With age and wear, unexpected brake locking became more likely with the designs that flirted with more "servo" in their geometry. Wiki also has a useful section, https://en.wikipedia.org/wiki/Drum_brake#Self-applying_characteristic [wikipedia.org]