Gear News

DT Swiss launch ARC wheels in conjunction with Swiss Side – the ‘new benchmark’ in aero wheels

"We’re breaking new ground in aerodynamic development with these wheels"

With the hashtag #flatoutfast accompanying the launch of DT Swiss’ new ARC wheels, you’d expect the aero hoops to come with some bold claims – and that proved to be the case. In fact, DT Swiss say the ARC wheels, developed in conjunction with Swiss Side, will become the benchmark by which aero wheels are judged.

DT Swiss have launched two new categories, with the all-new ARCs joined by the PRC wheels, which are an evolution of DT’s existing RC line-up. With the ARCs aimed at the aero market and the PRCs pitched as DT’s all-round ‘performance’ range, the Swiss firm’s carbon wheel collection is completed by the ERC endurance wheels we told you about last November.

DT Swiss first collaborated with Swiss Side on those ERC wheels and that partnership has been stepped up with the arrival of the ARCs. “We’re breaking new ground in aerodynamic development with these wheels,” says Swiss Side’s technical director, JP Ballard, who cut his teeth in Formula One before making the switch to cycling.

DT Swiss have once again joined forces with Swiss Side to develop the ARC aero wheels

Take your pick

Let’s take a closer look at the ARC wheels – described as the “new benchmark in the aero road cycling segment” by DT Swiss’ Alex Schmitt. The line-up is made up of six tubeless-ready wheelsets, with 80mm, 62mm and 48mm rim depths, available in rim brake and disc brake formats.

While the 48mm-deep rim is designed to offer aero performance and stability in gusty conditions, the 80mm option has been developed to maximise aero advantage, to the extent that DT Swiss say it creates a ‘sailing effect’ in certain wind conditions, propelling the rider forwards. Naturally, the 62mm hoops sit in the middle but DT say the overall weighted drag of the three wheelsets is within two watts. Take your pick based on your typical riding.

While they may differ in depth, all three rims share the same 17mm inner rim width – down 2mm on the ERC endurance wheels. “Rule number one in aerodynamics, frontal area is king,” says Ballard, and the 17mm rim width is said to offer ideal compatibility with 23mm and 25mm tyres. Ballard recommends running the ARCs with a 23mm tyre at the front to reduce the frontal area and 25mm at the rear to add a little more comfort into the mix.

Whether you choose the rim brake or disc brake wheels, the rim shape is identical and designed with a dual aerodynamic goal in mind: to reduce drag in the wind tunnel and increase stability out there in the real world.

Flat out fast?

The ARC rim profile is based on Swiss Side’s Hadron Ultimate 800, though DT Swiss say they’ve managed to increase performance by improving the ARC’s stall behaviour. Stall behaviour refers to the stability of the wheel, when the oncoming airflow angle is high enough that it does not hold onto the rim surface (thus detaching the flow). It’s the reason for that buffering effect you might have experienced with some deep-section wheels in blowy conditions.

This improvement is key, according to Ballard. Sixty-nine per cent of a rider’s effort goes into overcoming aerodynamic drag, compared to only 16 per cent for weight and 15 per cent for rolling resistance, and while the wheelset only makes up eight per cent of the overall drag package, the rider contributes 75 per cent, so by improving the wheelset’s stall behaviour – and crosswind stability – the rider should be able to stay in an aero position for longer.

Naturally, the ARC 1100 Dicut 48 wheels offer the best performance in blustery conditions, but in return, DT Swiss say the increased depth of the 62mm and 80mm wheels creates negative drag at high yaw (wind) angles – essentially working to push the bike and rider forwards – and a gain of up to ten watts with the 80mm wheels in the right conditions. That’s the sailing effect we were talking about.

Taking the deepest wheelset as an example, DT Swiss say the ARC 1100 Dicut 80 offers the same sailing effect as the Zipp 808 NSW, a wheelset DT refer to as the previous industry benchmark, but overall drag is reduced by one watt across yaw angles from -20 to +20 degrees. It’s a marginal gain, no doubt about that, but one which DT Swiss reckon translates into a drag reduction of 10 per cent.

Comparing the ARC 1100 Dicut 62 with the 53mm-deep Zipp 454 NSW, DT Swiss say their wheelset delivers a stronger sailing effect, thanks to the deeper rim, while offering the same stability, contributing to an overall reduction in drag.

Finally, as far as DT Swiss’ wind tunnel testing is concerned, the ARC 1100 Dicut 48 was pitched against the Zipp 454 NSW, and has a lower base drag level at zero degrees yaw, though the deeper (53-58mm) Zipp rim increases the sailing effect of the 454 NSW in some crosswind conditions. However, the key with the ARC 1100 Dicut 48, DT Swiss say, is in its all-round stable and predictable handling, ‘making it the perfect wheelset for gusty wind conditions’.

Translational drag and rotational drag

All things considered, DT Swiss reckon their new ARC wheels are the fastest on the market, whether by reducing drag, increasing the sailing effect, or improving stability – and sometimes a combination of all three.

Key to this, apparently, is the consideration of both translational drag and rotational drag during the development process. Translational drag is the aerodynamic force slowing the rider down from the front, and is what is typically tested in the wind tunnel, whereas rotational drag is the additional friction which occurs between the wheel and the air it passes through.

DT Swiss are quick to recognise that most leading aero wheels measure within one or two watts when it comes to translational drag, however they believe rotational drag – which is said to contribute up to 25 per cent to overall drag – has been neglected. “This is a new performance component we’ve developed as part of this project,” says Ballard.

DT Swiss developed a mobile test rig to measure rotational drag

DT’s engineers developed a mobile test rig to measure rotational drag. The wheel gets manually driven up to 60km/h, spinning on external bearings within the rig, and a light barrier measures the decline in speed to calculate rotational energy.

The result of DT Swiss’ testing means the ARC wheels have internal spoke nipples (contributing a 0.5-watt reduction in drag, apparently) and bladed DT Swiss Aerolite spokes (bringing another 1.5-watt drag reduction into the mix). The rim depth also has an influence on rotational drag – the deeper the rim, the lower the rotational drag, which ranges from 4.4 watts with the ARC 1100 Dicut 48 db wheels, to 4.13 watts for the ARC 1100 Dicut 80 db wheels.

Internal spoke nipples and bladed spokes may not be anything revolutionary, but DT Swiss say that by measuring rotational drag, they are able to quantify the influence of every component, in order to lower drag across the board. On top of that, they can use the data to guide further development, namely with spokes. Plans are afoot to develop new spoke shapes to further reduce rotational drag.

Disc brakes and hubs

You may also be wondering about the effect of disc brakes on drag. DT Swiss say their disc wheels have a higher drag of around two watts, compared to the equivalent rim brake hoops, and that’s as a result of the larger hub necessary for disc rotors.

Despite that, DT claim the aerodynamic behaviour is otherwise unaffected, with the drag curve and steering moment (which relates to stability) showing the same characteristics as the rim brake wheels.

As for the hubs, the wheels use DT’s Dicut Aero hubs, in their rim brake and disc brake configurations. The hubs spin on ceramic bearings and has been slimmed down as much as possible, with the aero-optimised hub shell said to reduce drag by around 0.4 watts. If you choose disc brake wheels, they run with DT Swiss’ RWS thru-axles – and if you really are counting every watt, the lever itself can be removed to reduce drag by a further 0.9 watts.

The ARC wheels are available in three depths – 80mm, 62mm and 48mm – and rim & disc brake formats

Pricing, weights and availability

DT Swiss ARC 1100 Dicut 48
Price: 2,388 euros (UK price TBC)
Weight: 1,470g

DT Swiss ARC 1100 Dicut 48 db
Price: 2,408 euros (UK price TBC)
Weight: 1,500g

DT Swiss ARC 1100 Dicut 62
Price: 2,388 euros (UK price TBC)
Weight: 1,620g

DT Swiss ARC 1100 Dicut 62 db
Price: 2,408 euros (UK price TBC)
Weight: 1,600g

DT Swiss ARC 1100 Dicut 80
Price: 2,388 euros (UK price TBC)
Weight: 1,750g

DT Swiss ARC 1100 Dicut 80 db
Price: 2,408 (UK price TBC)
Weight: 1,800g

All wheelsets will be available from October 2017.

What about the new PRC wheels?

As we mentioned at the top, DT Swiss have split their carbon road line-up into three ranges: Endurance, Aero and Performance.

The PRC – or Performance – wheels are based on the existing RC hoops and have no input from Swiss Side. Instead, the PRC wheels are described as an ‘evolution’ by DT Swiss, whereas they say the ARC hoops are a ‘revolution’. You’ll find four wheelsets in the range, in 35mm and 65mm depths, available in rim brake and disc brake versions.

One of the key differences between the PRC and ARC wheels is that the former are 1mm wider, with an internal rim width of 18mm – ideal, DT Swiss say, for use with 25mm tyres. That’s an indication of where DT see these wheels fitting in. While the ARCs are all-out aero wheels, the PRCs have more of an all-round flavour (and are considerably cheaper).

Still, the wheels have an NACA airfoil rim profile and stiffness is important too, with the hub flange distance increased by 0.8mm, increasing the spoke angle on the driveside by two degrees – something which DT Swiss say boosts the rigidity of the wheels. They’ve used continuous carbon fibres for the same reason.

Going back to the evolution of these wheels, and comparing the PRC 1400 Spline 35 wheelset to the RC 38 Spline hoops first introduced in 2013, DT Swiss say the latest design is one per cent heavier, but also 20 per cent wider and 15 per cent stiffer, while also using a resin 20 per cent more resistant to heat.