This Professor’s Bike Experiments Might Change the Way You Ride

Northeastern University professor Jim Papadopoulos wrote the book on bicycle dynamics. Decades into his career, he’s still tinkering away—and his five latest projects could shake up your bike life for the better

November 4, 2016
bike scientist

In 1966, seventh grader Jim Papadopoulos was riding his bike and looking down at his chainring, attempting to understand why his rear sprocket had fewer teeth, and how that affected their rates of rotation. So consumed was he with thoughts of his bicycle that he crashed into a parked car.

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For the next 50 years, bicycle mechanics would remain the vantage from which Papadopoulos approaches the world. The obsession carried him from the bike shops of his native Corvallis, Oregon, to the halls of MIT, where he began to question the accepted mathematical equations explaining how bicycles balance and handle. He co-authored Bicycling Science, in which he set fire to the prevailing mathematical understanding of bicycle dynamics and wrote his own equations, still accepted as bike-balancing law today.

Papadopoulos bike science
The scientist with his research subject. Photograph courtesy of .Jim Papadopoulos

Now 62, Papadopoulos is a professor of mechanical and industrial engineering at Northeastern University, where he’s collaborating with a group of savvy students and industry leaders to scientifically overturn conventional design principles governing numerous bicycle components—and perhaps the bicycle itself. If he’s successful (and if manufacturers and entrepreneurs adopt his findings), your next bike could handle better, brake faster, and even keep itself from falling over when you lose your balance.

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Here are five of Papaopoulos’ latest projects worth getting excited about: 

Project: Eliminating Shimmy

What It Is: “Shimmy is an uncontrolled, rapid oscillation of the steering that may occur at high speed and threatens to crash the bike,” Papadopoulos says. Those oscillations are also known as “death wobbles” to anyone who’s experienced them.

Why You Should Care: Because shimmy typically occurs at speed, the consequences of receiving a spontaneous high-velocity boot from the saddle can be seriously injurious, if not fatal. And no matter how expensive your frame, there is no known practical cure for shimmy (yet).


Project Status: The group is determining whether there’s a viable way to put one shimmy-crushing theory into play. 

“The [bicycle] has three rigid points of contact—two of those are each wheel in contact with the ground, and the third is the seat in contact with the rider,” says Papadopoulos’ sophomore student on the project, Brandon Goldstein, regarding the places the bicycle is firmly restrained to another object such as the ground or the rider. “We concluded that the only way to eliminate shimmy is by alleviating one of those rigid points.”

Since they can’t keep the wheels away from the ground, the group is focusing on the seatpost: If they can create a practical, affordable seatpost that eliminates that rigid point, they can effectively kill off the death wobbles. The project is currently in research and development, and they’re looking for an entrepreneur to adopt their soon-to-be-filed patent to bring the seatpost to market.

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Project: Making rim brakes work in the rain

What It Is: The idea came to Papadopoulos when he was racing bikes in 1974—back when bicycle disc brakes were not yet widely used. Rim brakes have lasted as long as they have because they do their job well and don’t weigh much, but they are particularly skittish in wet conditions. Even with the recent advent of disc brakes on road bikes, Papadopoulos wants to engineer a set of rim brakes that doesn’t lose stopping power in the wet.


Why You Should Care: Some newer road bikes come in disc-brake models, but most bicycles still come stock with rim brakes (as do most bikes in your parents’ shed). There’s an entire generation of bicycles that may still have you careening into a busy intersection given the presence of enough moisture.

Project Status: Papadopoulos is building on the work of Dave Wilson (a current MIT professor and the other co-author of Bicycling Science), who actually developed a rim brake that works in wet conditions by applying massive amounts of force to the rim—but the size and weight of the apparatus makes it impractical on the roads.

With the help of two former Cornell students, Papadopoulos built a motorized testing device that flushes the rim with water, and the team determined that the wet rims aren’t actually the problem: Dry brake pads exhibit the same stopping power when applied to both wet and dry rims, but drastically lose stopping power themselves when they get wet.

Now that those two students have graduated, he’s looking to recruit a new student or collaborator to design a brake pad that stays perpetually dry and works consistently in all conditions.

Project: Rear-Steering Bicycle and Steer-By-Wire Bicycle

What It Is: In March 1979, Wisconsin State Senator William Proxmire bestowed his uncoveted Golden Fleece of the Month Award—signifying egregious wastes of government funding—to a $120,000 Department of Transportation grant for the design of a backward-steering motorcycle, on the basis that it couldn’t be done. That didn’t sit well with Papadopoulos.

“I’m not swayed by people pontificating, saying ‘blah blah blah it is this way,’” Papadopoulos says. So he co-wrote a set of equations for a rear-steering bicycle with the help of Cornell bicycle researcher Andrew Ruina— and now Arend Schwab of the Bicycle Dynamics Lab at Delft University of Technology in the Netherlands is bringing it to life.

During the engineering process, however, Schwab discovered that the existing idea of how bicycles balance—with their wheels acting as a gyroscope—isn't quite accurate (see Schwab’s Ted Talk for more detail). This, combined with being able to design a rear-steering bicycle, inspired him to also begin designing a steer-by-wire bicycle, where electronics replace mechanical equipment. Schwab's hope is to build a bicycle that steers and balances with a set of motors and sensors, allowing the user to change the handling characteristics of the bike on the fly. He aims to answer the question: “How do you experience a vehicle? What is nice? What is difficult?”

Why You Should Care: Schwab admits that there isn’t much of a practical application for rear steering—although he says it took only two minutes for an untrained rider to adopt his prototype. The real value of the project is that it upsets traditional notions of balance, and proves the legitimacy of pursuing a self-balancing bicycle.

Project Status: Schwab is still in the conceptual stages of the steer-by-wire project.

taco wheel machine
The machine used to 'taco' wheels in the lab. Image courtesy of Jim Papadopoulos/Northeastern

Project: Defining wheel strength

What It Is: When a bicycle wheel fails, it folds laterally onto itself—or “tacos.” Papadopoulos enlisted the help of Matt Ford, a PhD student at Northwestern University, to write a set of easily digestible equations dictating the lateral strength of a wheel.

“I want this theory to be conceptual equations that can be understood very easily by someone who might be a bicycle enthusiast, but not an engineer,” Ford says.

Why You Should Care: The existing knowledge about wheel strength pertains to radial force (measured from the ground contact point to the hub), but we don’t know how much lateral force—which occurs in varying degrees in almost any crash, especially during a side-impact collision—is required to taco a wheel. If the Northwestern-Northeastern team can develop an “envelope” of force required to taco a wheel, they can integrate their findings into the design of a safer, more durable bike wheel.

Project Status: Right now, four of Papadopoulos’ students are putting together a testing apparatus that mimics the forces placed upon a taco’ing wheel. Once they can crush a wheel correctly, they’ll cross-reference their results with Ford’s.

“I have a bunch of theory and I have some equations,” Ford says. “I need to see real wheels fail in real ways.” 

If the students’ findings match Ford’s equations, they’ll confirm the definition of a safe wheel envelope.

Project: Manipulating Camber Thrust

What It Is: Camber thrust is the ability of a tire to generate force when leaned over during a turn. “When you lean a bicycle tire over, it has to drift outside of its line,” Papadopoulos says, “It does that because of a specific defect in the ability of the tire to generate thrust [propulsive force] when leaning over.” Ideally, the horizontal force (camber thrust) placed on the tire during a turn would equal the vertical force multiplied by the tangent of the lean angle—a fancy way of saying that the forces cancel each other out to keep the wheel aligned—but that lacking horizontal force explains the slip angle. He’s teamed up with Schwab and Andrew Dressel, a civil engineering and mechanics professor at the University of Wisconsin-Milwaukee, to figure out how to manipulate camber thrust.

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Why You Should Care: The defect means you lose energy in the turn and have poor directional precision, meaning hindered performance and handling. Road bike tires are the most susceptible to insufficient camber thrust because of their narrow width. Re-engineering a tire with less slip angle would mean improved handling in all bikes, but especially for roadies.

Project Status: Presently, the challenge is to conduct a test that holds the moving wheel in a specific orientation, and that means eliminating slip angle, or the difference between the angle at which the wheel is traveling and the angle at which the wheel is pointed.

Dressel just completed his third iteration of a testing rig that can do just that: isolate the movement of the frame and the wheel, and measure the lateral force required to generate camber thrust. Dressel and Papadopoulos co-presented a related paper at the Bicycle and Motorcycle Dynamics Symposium in September, which built on existing camber and compression analysis to derive mathematical expressions that explain the behavior of the whole tire. The paper provides a platform for more accurate tire modeling and the eventual creation of better-handling bike tires.

Author’s note: Papadopoulos is currently seeking collaborators and students for these and other projects. Interested parties should email him at [email protected]