Aerodynamicist Luisa Grappone DesignsFatter Yet Faster Bicycle Wheels

Aerodynamicists—like Luisa Grappone—are hot property in the bicycle industry. They design products that make cyclists faster through the air.

Air has heft: at nine miles per hour it becomes the dominant force of resistance, and by the time a cyclist hits 30mph, 90% of pedaling power goes into overcoming what is known as aerodynamic drag. An aero-optimized bicycle can shave not seconds but some minutes off a ten-mile time trial. (It could also get you to work faster if you were willing to fold your torso into an aero “tuck.”)

Many bicycle industry aerodynamicists, Grappone included, have aviation backgrounds. The Italian composites specialist has an MSc in aerospace engineering but found airplane making less than stimulating.

“I was doing stress analysis on the fuselage of the Boing 787 [Dreamliner],” she tells me at a bicycle press event in Idaho.

“But that was really boring—I couldn’t see [the full picture of] the component I was working on.”

A competitive cyclist, she transferred into the cycle industry working first for high-end Italian cycle component manufacturer 3T. She later worked for fellow Italian bicycle brand Campagnolo. Some of the wheels she helped to perfect in wind-tunnel testing were ridden today in the Tour de France time trial in Pau, France.

Two years ago she moved to Brighton, England, to work for startup bicycle components company The Rider Firm, maker of Hunt Wheels.

If you pardon the pun, there’s a bicycle wheel revolution happening. Last year the world governing body of cycle sport allowed professional racers to ride with disc brakes instead of traditional rim-activated brakes. While mountain bikers have benefitted from the greater stopping power of disc brakes for many years, the UCI had forbidden their use in the professional peloton. This was a dampener on sales of “road disc” bikes to mere mortals.

With the lifting of the ban, new bicycle frame shapes have been developed which tuck disc brakes away, hiding them from the air. Removing the rim brake from the front of the bike also results in a cleaner frontal area for pushing air out of the way. And with no more need to consider rims as braking surfaces they, too, can be redesigned, making them more aero.

Perhaps surprisingly, the new designs becoming common in the industry are fatter than previous ones, yet wind tunnel tests confirm these wider wheel rims are more aero.

As well as wider rims, tires have also been getting fatter in recent years. In the 1970s, pro riders shook their bones to bits by riding with almost-solid 19mm-wide tires, assuming that the narrower and harder the tire the greater the speed.

Recent testing of “rolling resistance” has found that wider, softer tires are, in fact, faster, as well as offering more comfort and—critically—more traction.

Tires have therefore been getting wider, and riders no longer demand rock-solid air pressures.

Until recently most pro riders—and most serious amateurs—rode on 23mm tires, pumped up to 100psi or more. Many now prefer tires up to 28mm wide, especially now that wind tunnel and rolling resistance testing is showing that wider softer tires aren’t necessarily slower tires.

Grappone grapples with the wheel-to-air interface every day, perfecting rim shapes out of composites and comoulded materials to allow cyclists to go faster.

Using a new—and patented— process, Hunt Wheels has incorporated a low density expanded polymer into a carbon composite rim to make a 50 gram weight saving on what would been an already lightweight aero wheel. (Rotating mass has a massive effect on ground speed, so lighter wheels are faster wheels.)

Free of the rim brake restraint, the new Hunt Wheels 48 Limitless Aero Disc wheel “allows for low weight and extra-wide aerodynamics,” states the Brighton company. The 48 stands for the 48mm depth of the wheel rim, said to be the optimum depth for strength but not so deep that it is deflected by crosswinds, a bugbear of earlier deep rims.

(In yaw testing developed by French bicycle company Mavic, aero wheels are judged not only when traveling straight on into the wind but also when riding into a crosswind.)

Hunt Wheel’s new rim is wider than the tire, yet still aero.

“We’ve been working hard in the wind tunnel, testing these rims against great competitors like Zipp, Enve, DT Swiss, Mavic,” says Grappone, adding that “we are the best so far with an under-50 millimeters rim.”

Zipp, Enve, DT Swiss, Mavic are mainstream names in the bicycle industry and have been working on aero wheels for many years so this is a bold claim for the startup.

The Rider Firm

Hunt Wheels was created in 2014 by brothers Tom and Pete Marchment. The Rider Firm—the company which owns the Hunt Wheels brand name—sprang from a low-tech business selling bicycle innertubes online. “We cut out the middlemen to bring you great quality inner tubes for less,” boasted the fledgling discounter, much to the annoyance of bike shops.

The innertubeshop.com is no longer trading but was a route into the bicycle industry for Pete, a materials scientist with a masters degree in natural sciences from Cambridge University.

Tom has a long background in the bicycle industry. Despite being retired, their father, John, also helps out with the business. Another materials engineer, he was a former production manager at a company which produced an early composite chassis for the Alfa Romeo Formula One car.

“Pete launched the innertubeshop.com in the garage when he was living in the spare room in my house,” remembers Tom Marchment.

“At the time, [bike shops] were charging quite a lot for inner tubes. Pete decided to innovate on price. In 2014 I joined him to diversify into wheels.”

The Rider Firm grew quickly, making a name for itself as a nimble operator. Grappone joined in 2017 to develop the company’s aero wheels.

“We’re all riders,” says Pete Marchment. “We can see the trends coming, and we’re close to the customer because we’re responding to people on social media, and dealing with those orders directly. We don’t have a separation of three, four, or five layers between the customer and us.”

Grappone left her native Italy to work for The Rider Firm because “the industry was talking about these guys in the U.K. doing cool stuff. I told them I have some really [innovative] ideas [for aero wheels] and we went straight to the wind tunnel to test them.”

The 48 Limitless wheel was the result, with other aero wheels in the pipeline. Hunt Wheels are now available worldwide.