British bike innovators Parcours has unveiled its new gravel racing bike, boldly claiming it’s the first of its kind.
“The FKT wheelset is the first truly aero-optimized gravel bike. Rather than trying to mitigate the aerodynamic penalty of a gravel tyre, FKT is all about optimizing gravel racing performance,” the brand says, backing up its claims and findings with a white paper on its design philosophy, process and wind tunnel testing. .
In its white paper, the brand concludes that when it comes to winning gravel races, aero really is everything.
“It’s clear to see that the gravel racer has significant aerodynamic performance advantages,” he states. “To put the magnitude of the benefit into perspective, the performance benefit of the FKT over the previous generation of gravel race wheels is akin to going from a low-profile climbing or training wheel on a time trial bike to a full race setup of deep wheels. front and rear disc wheel section’.
However, the main role is played by the matching of tires and wheels. So Parcours specially designed the FKT bike around the new 40mm wide Gravelking X1 Panaracer tire. The Parcours is not unique in recognizing the importance of tire profile and rim interaction when it comes to aerodynamics. And we are seeing an increase in partnerships between wheel and tire manufacturers (ie DT Swiss and Continental) or bike brands launching their own tires (ie Enve)
Based on its studies, Parcours estimates that using FKT wheels paired with GravelKing X1 tires would save nearly 12 minutes over the previous generation of gravel wheels paired with a higher-tread tire in a 200-mile Unbound event. In this year’s race, that time difference would be the difference between first and 16th in the men’s race or first and 15th in the women’s race.
“The performance benefit of an aerodynamically optimized gravel bike cannot be understated,” concludes Parcours.
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When it comes to winning gravel races, aero is everything
The Parcours FKT bike spotted on Unbound Gravel in June
(Image credit: Anne-Marije Rook)
The growth and professionalization of gravel racing is pushing off-road product innovation to be faster and more efficient. With riders now covering the 200 mile course in just over 9 hours, speed is of the utmost importance and attention inevitably turns to aerodynamics.
Parcours already catered to the adventure side of gravel riding with its Alta bikes, but as its sponsored athletes looked for ways to optimize their setups, the engineers – already experienced in aerodynamics – got to work.
However, it quickly became apparent that the design for road and gravel aerodynamics was significantly different.
First, Parcours designed their road bikes with the philosophy that the optimal rim width should be slightly wider than the tire width. Since 40mm+ tires are the norm on gravel, the resulting super wide rims would require more material, which in turn means increased weight, reducing the aerodynamic benefits. Additionally, the wider outer rims make it more difficult to keep the inner rim width in line with ETRTO guidelines.
Regarding rim depth, previous studies by Parcours found that the ideal ratio of rim depth to tire width began to show diminishing returns at >4:1 (depth:width). Using the 28mm tire as a benchmark on the road led to the creation of the Chrono Max, the brand’s fastest bike, featuring a rim depth of 83.6mm. However, for 40mm+ gravel tires this would mean a total rim depth of 120mm+, again adding weight and negatively impacting the bike’s handling.
But perhaps the biggest challenge was considering the tread patterns and their wide variations.
So with these challenges in mind, Parcours set the design parameters:
- Maximum outer rim width set between 40-45mm for frame clearance.
- Inner rim width set to 27mm to accommodate a range of tire widths.
- Utilizing Kamm’s hybrid tail design to balance aerodynamic benefits and practical rim depth.
- Optimizing the design around one particular tire tread rather than the width of the tire. Parcours chose the Panaracer GravelKing X1 for its versatility and low rolling resistance aggressive tread balance.
- Driving conditions. Parcours reports that real-world wind data indicated that in a gravel racing environment there is significantly less difference in yaw conditions – the angle between the wind direction and the forward motion of the motorcycle – compared to road racing.
Prototypes were designed using NACA airfoil profiles and 3D CAD modeling and tested using computer simulations (Computational Fluid Dynamics). The final designs were tested in the A2 wind tunnel in North Carolina against the competition, other Parcours bike models and different tire profiles.
Here, the FKT proved significantly faster than the brand’s Ronde wheelset, as well as the popular Zipp 303 Firecrest wheelset, both shod with the same X1 tire at the same tire pressure.
(Image credit: Parcours)
What most interested the test team was the impact of tire selection and tire/wheel combinations.
“The decision to run the 45mm GravelKing X1 ahead of the 40mm GravelKing X1 would result in an estimated time penalty of 2 minutes 36 seconds on Unbound Gravel,” the team concluded. “However, with the associated improvements in traction and control, it may become the preferred setup in certain circumstances and for some races.”
Comparing the Panaracer GravelKing X1 with other popular models revealed more substantial differences.
(Image credit: Parcours)
“The more pronounced tread of the ‘high’ tread tire tested the slowest, while the ‘low’ tread tire found a difference in performance. Despite this, the GravelKing X1 remained by some distance the most aerodynamic tire when mounted on an FKT wheel,” the testing concluded.
As mentioned earlier, the Parcours study highlights the importance of tire and rim compatibility, especially on the gravel side.
Two-wheeler Parcours FKT
Parcours FKT bike on Specialized Crrux
(Image credit: Parcours)
The final product has already secured a win and a Top 10 in the UCI Gravel World Series and a podium in the Migration Gravel Race for athletes Maddy Nutt and Joe Laverick.
The FKT wheels feature a hybrid shape with a shortened virtual foil designed to direct airflow from the wider tire and reduce the turbulence caused by the non-slip tread required for riding on gravel. And unlike the aerodynamic Parcours road bikes, the FKT bike has a symmetrical front and rear rim.
The FKT has a hookless rim with an internal width of 27mm and is ETRTO compatible from tire widths of 35mm and up. It also includes the same IMPACT+ technology found on Parcours’ existing Alta rims, which uses a more flexible resin on the edge of the rim to increase durability and impact resistance.
The hubs used in the FKT are the same as the Parcours road disc models, with the drivetrain featuring a 6-pawl freehub running on a 44T ratchet ring.
FKT bikes are available for pre-order until July and will ship in August. All bikes ordered during the pre-order period will include a pair of Gravel King X1 tires.
Details:
- Price: £1,199 / $1,599 / €1,559
- Weight: 1,500g
- Rim depth: 47.0 mm
- Maximum rim width: 40.0 mm
- Inner rim width: 27.0 mm
- ETRTO compatible with 35mm+ tires