British wheel refining company Parcours has unveiled its new gravel racing wheelset with the bold claim that it is the first of its kind.
“The FKT wheelset is the first truly aerodynamic gravel wheel. Rather than trying to mitigate the aerodynamic penalty of a gravel tire, the FKT is all about optimizing performance in gravel racing,” says the brand, which backs up its claims and findings with a whitepaper detailing its design philosophy, process, and wind tunnel testing.
In the white paper, the brand concludes that aerodynamics are indeed everything when it comes to winning gravel races.
“It is clear that there are significant aerodynamic performance advantages available to a gravel racer,” it reads. “To put the magnitude of the advantage into perspective, the performance advantage of FKT over a previous generation of gravel race wheels is comparable to going from a low-profile climbing or training wheel on a time trial bike to a full-on race setup of deep-section front and rear disc wheels.”
The tire and wheel combination plays an important role, however. That’s why Parcours designed the FKT wheel specifically around Panaracer’s new 40mm-wide Gravelking X1 tire. Parcours isn’t alone in recognizing the importance of how a tire tread and rim work together when it comes to aerodynamics. And we’re seeing an increase in partnerships between wheel and tire manufacturers (e.g. DT Swiss and Continental) or wheel brands bringing their own tires to market (e.g. Enve)
Based on its studies, Parcours estimates that running the FKT wheelset with GravelKing X1 tires would save nearly 12 minutes over running a previous-generation gravel wheel with a deeper-tread tire at the 200-mile Unbound event. At this year’s race, that time difference would have been the difference between first and 16th in the men’s race, or first and 15th in the women’s race.
“The performance advantage of an aerodynamically optimized gravel bike should not be underestimated,” Parcours concludes.
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When it comes to winning gravel races, aerodynamics is everything
The Parcours FKT wheelset spotted at Unbound Gravel in June
(Photo: Anne-Marije Rook)
The growth and professionalization of gravel racing is driving innovation in off-road products faster and more efficiently. With riders now covering a 200-mile course in just over 9 hours, speed is of the essence and the focus inevitably shifts to aerodynamics.
Parcours was already focused on the adventure side of gravel riding with its Alta wheelset, but when its sponsored athletes started looking for ways to optimize their setup, the engineers – who already had experience in aerodynamics – got to work.
However, it soon became clear that designing for aerodynamics on the road and on gravel is a fundamental difference.
Firstly, Parcours designed their race wheels around the philosophy that the optimal rim width should be slightly wider than the tire width. However, since 40mm+ tires are the norm for gravel, the resulting super-wide rims would require more material, which in turn adds weight, compromising the aerodynamic benefits. Additionally, wider external rims make it difficult to maintain an internal rim width that meets ETRTO guidelines.
In terms of rim depth, Parcours’ previous research found that the ideal ratio of rim depth to tire width began to show diminishing returns at >4:1 (depth:width). Using a 28mm tire as a road benchmark led to the creation of the Chrono Max, the brand’s fastest wheel, with a rim depth of 83.6mm. However, for 40mm+ gravel tires, that would mean an overall rim depth of 120mm+, again adding weight and negatively affecting the bike’s handling.
But perhaps the biggest challenge was mapping the tread patterns and the wide variations within them.
With these challenges in mind, Parcours established design parameters:
- Maximum outer rim width for frame clearance is 40-45mm.
- The internal rim width is set at 27mm to accommodate different tire widths.
- Utilizing a hybrid Kamm tail design to balance aerodynamic benefits and practical rim depth.
- Optimizing the design around a specific tire profile instead of tire width. Parcours chose the Panaracer GravelKing X1 for its versatility and a balance between aggressive tread and low rolling resistance.
- Riding Conditions. Parcours states that real-world wind data indicated that there is a significantly smaller difference in yaw conditions – the angle between the wind direction and the forward motion of the bike – in gravel racing environments compared to road racing.
Prototypes were designed using NACA airfoils and 3D CAD modeling and tested using Computational Fluid Dynamics (CFD) simulations. The final designs were tested in the A2 Wind Tunnel in North Carolina against a competitor, other Parcours wheel models and different tire profiles.
The FKT proved significantly faster than the brand’s Ronde wheelset and the popular Zipp 303 Firecrest wheelset, both equipped with the same X1 tire and the same tire pressure.
(Image credit: Parcours)
What intrigued the test team most was the impact of tire choice and tire-wheel combinations.
“Opting for a 45mm GravelKing X1 instead of a 40mm GravelKing X1 would result in an estimated time penalty of 2 minutes and 36 seconds on Unbound Gravel,” the team concluded. “However, with the associated improvement in traction and control, this could become the preferred setup in some conditions and for some races.”
When comparing the Panaracer GravelKing X1 with other popular models, more significant differences emerged.
(Image credit: Parcours)
“The more pronounced tread on the “High” tread tire tested the slowest, while a significant difference in performance was shown by the “Low” tread tire. Despite this, the GravelKing X1 remained by far the most aerodynamic tire when mounted on an FKT wheelset,” the test concluded.
As noted earlier, Parcours’ research underscores the importance of tire and rim compatibility, especially when riding gravel.
The Parcours FKT wheelset
Parcours FKT wheelset on a Specialized Crrux
(Image credit: Parcours)
The end product has already resulted in victories and top 10 finishes in the UCI Gravel World Series and a podium finish at the Migration Gravel Race for athletes Maddy Nutt and Joe Laverick.
The FKT wheels feature a hybrid, truncated virtual foil shape, intended to manage the airflow of a wider tire, reducing turbulence caused by the non-smooth tread pattern required for gravel riding. And unlike Parcours’ aero wheelsets, the FKT wheelset features a symmetrical front and rear rim.
The FKT has a hookless rim with an internal width of 27mm and is ETRTO-compliant from a tire width of 35mm. It also features the same IMPACT+ technology as in Parcours’ existing Alta rims, which uses a more flexible resin at the rim edge to increase durability and impact resistance.
The hubs used in the FKT are the same as those used in Parcours disc brake models, with a drive mechanism consisting of a 6-pawl freehub running on a 44T ratchet ring.
FKT wheels are available for pre-order until July for August delivery. All wheelsets ordered during the pre-order period will include a pair of Gravel King X1 tires.
Details:
- Price: £1,199 / $1,599 / €1,559
- Weight: 1,500 g
- Rim depth: 47.0 mm
- Maximum rim width: 40.0 mm
- Inner rim width: 27.0 mm
- ETRTO compliant with 35mm+ tyres