Cyclist
Parcours’s new FKT gravel wheels are aero-optimised for 40mm tyres
Parcours has launched an aero-optimised gravel bike wheelset called the FKT, for Fastest Known Time, working with Panaracer’s GravelKing X1 tyres to provide an aero profile that works with wider, treaded gravel bike tyres.
The new FKT wheelset has a 1,500g claimed weight, 27mm internal width and 47mm depth and is priced at £1,199 / $1,599 / € 1,599. Orders can be placed now but stock will be available from August 2024.
Aero-optimised wheel-tyre combination
Parcours claims that gravel wheels are mainly designed to reduce the drag inherent in wider, knobblier gravel bike tyres. In contrast, the brand has aimed to aero-optimise the gravel tyre and wheel combination.
It’s tricky however, as Parcours says it has found that the best aero performance is obtained with a rim that’s slightly wider than the tyre.
Once you get up to 40mm tyre width, that means a lot of mass in the rim. It also makes it difficult to produce a rim with an internal width that’s in line with ETRTO guidelines. If you tried to meet both objectives, you could end up with a rim that’s not aero at the rim-tyre junction.
Another design constraint is rim depth, which Parcours reckons needs to be around 4:1 for the best aero gains, implying a rim depth of 120mm for a 40mm gravel bike tyre – clearly impracticable for weight and crosswind stability reasons.
Parcours’s solution is a ‘hybrid truncated virtual foil’ aero shape, which it says helps to manage airflow around the wider gravel bike tyre and reduce turbulence caused by the tyre’s tread. It’s not a kamm-tail, as although this would provide aero gains at the leading edge of the wheel, it would present a blunt profile to the wind at the trailing edge.
Aero-optimised around 40mm Panaracer GravelKing X1 tyres
Parcours has paired with Panaracer, using its latest GravelKing X1 all-rounder gravel tyre in 40mm width as its starting point for the aero-optimisation, as it’s a popular choice for racing. However Parcours says its new wheels will work as well with gravel bike tyres between 35mm and 45mm width.
Wind-tunnel tests were carried out pairing the FKT rim profile with three other 40mm tyres: the Schwalbe G-One RS Evo Race, WTB Riddler and Pirelli Cinturato RC X. All showed increased drag over the GravelKing X1 on its rims of between 10 watts and 15.3 watts at 48kmh.
Parcours reckons that this might add between 4.1 and 6.3 minutes to ride times at Unbound 200.
It believes that tread pattern and height of the knobs at the edge of the tyre – where they’re typically taller for grip – were the major determinants of wheel-tyre drag.
Hookless 27mm internal width
The new Parcours FKT rim has a 27mm internal width and is hookless, which according to ETRTO standards allows it to be used with tyres of 35mm width or greater. The rim is 47mm deep and the claimed wheelset weight is 1,500 grams.
Parcours’s road bike wheels have different profiles for the front and rear rims, as it has found that the wind yaw angles experienced are significantly different.
When it repeated its yaw angle tests on gravel, it found that there was little difference between front and rear wheel wind yaw angles, so the new FKT rims have the same profile front and rear. Parcours believes its findings are due to a combination of lower average speeds, more sheltered conditions and more disrupted airflow from the non-smooth surface and the tyre’s characteristics.
Parcours has incorporated its Impact+ tech in the new wheels, which uses a more flexible resin at the edge of the rim for greater impact resistance – a useful quality in gravel bike wheels.
At their centre, the FKT wheels have the same Parcours Road Disc hubs with a 44-tooth 6-pawl freehub as used in its Strade road wheelsets.
Parcours says that its new wheels have been used by its sponsored gravel racers, Maddy Nutt and Joe Laverick, who have gained race wins, podiums and top tens on them.
Price and availability
If you’re planning to chase an FKT, the new wheels can be pre-ordered now, with delivery in August. They’re priced at £1,199 / $1,599 / € 1,599.
Orders placed in July will be delivered with a free set of Panaracer GravelKing X1 tyres.
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