There’s a certain irony to the fact that while bicycle technology is a field of ever-changing, ever-improving gear, bicycle fit evolves at a pace only slightly quicker than the evolution of bodies themselves. While the tape measure was the primary tool of the fitter until the late 1990s, the goniometer—kind of a fancy protractor that allows fitters to measure body angles—has been the basic tool of the fitter since the Clinton administration. I almost never approach a person with a tape measure; that’s for the bike, not the body.
Efforts to make fit more scientific, to better match the bike to the body have certainly cut down on the number of bad fits I see, but merging bike fit with rider aerodynamics has been guesswork unless you’re a pro on a big-budget team that buys wind tunnel time. Until now, that is.
Ingmar Jungnickel is an aerodynamicist who has introduced a new way to approach fit with his service, called AiRO. Jungnickel’s credentials make him the ideal person to do such a thing. He’s a German-born-and-educated engineer who went on to run Specialized’s Win Tunnel before moving to Utah to work with the U.S. Olympic program, doing things like making speed skaters cut seconds—yes, full seconds, sometimes multiples of them—from their times. How much faith does the U.S. Olympic Committee place in him? He was named the USOC’s 2018 Sports Science Coach of the year.
AiRO is a computational fluid dynamic (CFD) application that creates an avatar of the rider from photographs and then positions them on a virtual bike and “blows” them in a virtual wind tunnel. Incredibly, the software can perform a staggering amount of math is just seven minutes, less time than it takes to bake a pizza.
It wasn’t that long ago that the idea that CFD software could blow a rider on a bike and finish the computation prior to the end of the rider’s life was laughable. In 2008, I was working for Felt Bicycles and they were one of the first companies to actually use CFD in product design (Zipp was another). Back then, Felt’s engineers would set up a script to virtually blow one tube of a bicycle, say the down tube. The script would indicate which yaw angles (typically something like 0, 15, 30, 45, 60 and 90. They would hit “run” at 5:00 on Friday and pray that the computer would be finished by Monday morning. The idea of blowing an entire frame was unthinkable. That AiRO can test a complete bicycle with rider shows just how far computing power has come since then.
Practicality
Making riders more aerodynamic has generally come down to making the bicycle more aerodynamic. Why? There have been a few reasons. First is that wind tunnel time is stupid expensive and while the wind tunnel may charge thousands of dollars per hour for testing, wind tunnels are usually rented in single day increments. And because wind tunnels number in the dozens worldwide, wind tunnel time usually also requires plane tickets. So getting time in a wind tunnel is flat-out impractical. This would be why many bike companies would only test their products once, at the end of the development cycle, once they are ready to go to market with the product.
True wind tunnel testing requires designers to create a product, make a mock-up, blow it in the wind tunnel, analyze the data, go back to their work stations, make changes, make a new mock-up and then blow it. Rinse, repeat. Due to the expense and complication of testing most bike companies have done what would be more properly termed “wind tunnel examination.” Per the industry’s marketing speak, blow a product once and the company can call it “wind tunnel tested.”
Perspective
Despite the remarkable aerodynamic gains that manufacturers have made in rim, frame and helmet design, making a bike more aerodynamic leaves the greatest gains possible on the table. The rider is where the most significant gains can be made. According to Jungnickel, the average rider realizes a 26-watt savings. Considering the 3-watt savings that comes with some ceramic bearings, or the 2-watt savings with some chain lubricants/methods, an aerodynamic fitting guided by AiRO punks a whole suite of marginal gains. And let’s consider that dropping $300 on a fitting is a good deal more affordable than a new set of wheels.
The Fitter’s Role
You may wonder why a qualified fitter is still considered necessary considering that AiRO does the heavy math. Couldn’t someone with a set of wrenches submit materials to Jungnickel and company and then make the changes necessary to their bike? The fitter is necessary because even after getting results from AiRO, the fitter serves as the diplomat negotiating between the rider’s flexibility and the AiRO recommendations. The more a rider approaches a flat-backed position, the harder it is to generate power. Simply put, as a fitter, I can put you in a very aero position without the aid of AiRO, but you may not be able to pedal. The point of AiRO is to aid the fitter in finding the fastest compromise between optimal power production and reduced frontal area.
One thing I learned in visiting San Diego’s Low-Speed Wind Tunnel with Felt was that what’s fastest isn’t necessarily intuitive. Even the best engineers can’t look at a product and tell you if it will be fast. One of the interesting findings of Jungnickel’s work has been that there’s not much point to running a narrow bar if you have wide hips. Running a wider bar can result in better aerodynamics and it can also mean opening up the rider’s chest for deeper, more complete breathing. Win, win. Had I not spent time watching engineers work with an Olympic athlete to position them in as aerodynamic a position as possible, I’m not sure I’d be as a ready to believe in the promise of AiRO, but I have, and I have witnessed how pulling elbows in or tipping the head down can make a huge difference.
Chewing on Coins
The way AiRO works, a fitter has to purchase a package of fits, a set number of which the smallest package is 50 fits, which is why an individual can’t simply purchase one online. The upshot is a several thousand dollar investment in the system for a fitter, at minimum. I’m impressed enough with what I’ve seen that I plan to go through the certification process and will make the investment to begin offering these fits. As we like to say, there’s no better testimonial than putting your money where your mouth is.