Aero is everything: Parcours introduces the FKT wheelset, aero gravel hoops promising tangible gains

British wheel innovators Parcours has unveiled its new gravel race wheelset with the bold claim of being a first of its kind. 

“The FKT wheelset is the first truly aero-optimised gravel wheel. Rather than looking to mitigate the aerodynamic penalty of a gravel tyre, the FKT is all about optimising performance in gravel racing,” the brand states, backing up its claims and findings by releasing a white paper of its design philosophy, process and wind tunnel testing.

In its white paper, the brand concludes that when it comes to winning gravel races, aero is indeed everything. 

“It is clear to see that there are substantial aerodynamic performance benefits available to a gravel racer,” it states. “To put the size of the benefit into perspective, the performance benefit of FKT over a previous generation of gravel race wheel is similar to moving from a low-profile climbing or training wheel on a time trial bike to a full race setup of deep-section front and rear disc wheel.” 

However, the tyre-and-wheel pairing plays a major role. Thus, Parcours specifically designed the FKT wheel around Panaracer’s new Gravelking X1 tyre in 40mm width. Parcours is not unique in recognising the importance of how a tyre profile and rim interact when it comes to aerodynamics. And we’ve been seeing an increase in partnerships between wheel and tyre manufacturers (i.e. DT Swiss and Continental) or wheel brands bringing their own tyres to market (i.e. Enve) 

Parcours estimates, based on its studies, that using the FKT wheelset paired with GravelKing X1 tyres would save nearly 12 minutes over a previous generation gravel wheel paired with a higher tread tyre at the 200-mile Unbound event. At this year’s race,  that time difference would have been the difference between a first and a 16th-placed finish in the men’s race, or the first and 15th-placed finisher in the women’s race.

“The performance benefit of an aerodynamically-optimised gravel bike cannot be underestimated,” Parcours concludes. 

When it comes to winning gravel races, aero is everything 

The growth and professionalisation of gravel racing is pushing the innovation of off-road products to be faster and more efficient. With riders now tackling 200–mile course in a little over 9 hours, speed is of the utmost importance and inevitably, the focus turns to aerodynamics. 

Parcours already catered to the adventure side of gravel riding with its Alta wheelset, but when its sponsored athletes came looking for ways to optimise their setups, the engineers –already experienced in aerodynamics– got to work. 

However, it quickly became clear that designing for aerodynamics on the road and gravel are vastly different.

For one, Parcours designed its road wheels around the philosophy that the optimal rim width should be slightly wider than the tyre width. With 40mm+ tyres being the norm in gravel, however, the resulting super wide rims would necessitate more material, which in turn means added weight, detracting from the aero benefits.  Additionally, wider external rims make it challenging to maintain an inner rim width compliant with ETRTO guidelines.

Regarding rim depth, Parcours’ previous studies found that the ideal rim depth-to-tyre width ratio started showing diminishing returns at >4:1 (depth:width). Using a 28mm tyre as a benchmark on the road led to the creation of the Chrono Max, the brand’s fastest wheel, which features an 83.6mm rim depth. However, for gravel tyres of 40mm+, this would imply a total rim depth of 120mm+, which would, again, add weight and negatively affect bike handling.

But perhaps the greatest challenge was considering tread patterns and their extensive variations.

So, with these challenges in mind, Parcours established design parameters:

• Maximum external rim width set between 40-45mm for frame clearance.
• Internal rim width set to 27mm to accommodate a range of tyre widths.
• Utilising a hybrid Kamm tail design to balance aerodynamic benefits and practical rim depth.
• Optimising the design around one specific tyre tread rather than tyre width. Parcours chose the Panaracer GravelKing X1 for its all-roundedness and a balance of aggressive tread with a low rolling resistance.
• Riding conditions. Parcours states that real-world wind data indicated that, in gravel racing environments, there is a significantly reduced difference in yaw conditions – the angle between the direction of the wind and the bike’s forward motion– compared to road racing.

Prototypes were designed utilising NACA airfoil profiles and 3D CAD modelling and tested using computer simulations (Computational Fluid Dynamics). Final designs underwent testing in North Carolina’s A2 Wind Tunnel against a competitor, other Parcours wheel models and different tyre profiles.

Here, the FKT proved significantly faster than the brand’s Ronde wheelset as well as the popular Zipp 303 Firecrest wheelset, both fitted with the same X1 tyre at the same tyre pressure.

 What intrigued the test team most was the impact of tyre choice and tyre-wheel combinations.

“Choosing to run a 45mm GravelKing X1 over a 40mm GravelKing X1 would lead to an estimated time penalty of 2 minutes 36 seconds at Unbound Gravel,” the team concluded. “However, with the associated improvement in traction and control, in some circumstances and for some races this may become the preferred setup.”

Comparing the Panaracer GravelKing X1 with other popular models revealed more substantial differences.

“The more pronounced tread on the “High” tread tyre tested the slowest, whilst there was a material difference in performance shown by the “Low” tread tyre. Despite this, the GravelKing X1 remained by some distance the most aerodynamic tyre when fitted to an FKT wheelset,“ testing concluded.

As noted earlier, Parcours’ study underscores the importance of tyre and rim compatibility, especially in the gravel side of things.

 The Parcours FKT Wheelset 

The final product has already secured wins and Top 10s in the UCI Gravel World Series and a podium at the Migration Gravel Race by athletes Maddy Nutt and Joe Laverick.

The FKT wheels feature a hybrid, truncated virtual foil shape, meant to manage airflow from a wider tyre, reducing turbulence caused by the non-slick tread pattern required for gravel riding.  And unlike Parcours’ aerodynamic road wheelsets, the FKT wheelset features a symmetrical front and rear rim.

The FKT features a hookless rim with a 27mm internal width and is ETRTO compliant from a 35mm tyre width upwards. It also incorporates the same IMPACT+ technology seen 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 found in Parcours' road disc models, with a drive mechanism that includes a 6-pawl freehub running on a 44T ratchet ring.

FKT wheels are available for pre-order through July for delivery in August. All wheelsets ordered during the pre-order period will include a pair of Gravel King X1 tyres.

Details:

• Price: £1,199 / $1,599 / €1,559
• Weight: 1,500g
• Rim depth: 47.0mm
• Max rim width: 40.0mm
• Internal rim width: 27.0mm
• ETRTO compliant with 35mm+ tyres