Road Revolution 18

#Flatoutfast

Aero
Category

Aerodynamics describe the interaction of an object with its surrounding medium: air. To us, aero means minimal drag in all conditions, allowing you to go faster than ever. Without any compromises in handling, stiffness and braking performance, creating the most efficient and complete system.

ARC 1100 DICUT®

ARC 1100
DICUT®

The Line up

The ARC 1100 DICUT® wheels are made to go flat out fast. Available in three different rim depth – 80, 62 & 48 mm – and rim brake as well as disc brake versions our new aero line-up leaves nothing to be desired. Supreme aero-stability and minimal aero drag support the complete system of the rider and his bike. Built up from highest quality DT Swiss components the ARC 1100 DICUT® wheels give you the reliability you need – no matter if it’s for a 180 km IRONMAN bike split or your local time trail.

ARC 1100 DICUT® 80
ARC 1100 DICUT® 80

If going flat out fast is what you want, then this wheelset has all the details covered. Our top triathletes choose the ARC 1100 DICUT® 80 wheelset when it’s race day. Developed in partnership with aerodynamics specialists Swiss Side and equipped with SINC Ceramic bearings to get up to speed and stay there. Supporting the complete system of the rider and his bike with minimal drag and unparalleled handling under all conditions, riding fast is guaranteed. Finally the precision wheel build with high and even spoke tension gives you the reliability to dominate all of the 180 km bike course.

ARC 1100 DICUT® 62
ARC 1100 DICUT® 62

Aero meets all-around: the ARC 1100 DICUT® 62 is ridden by our athletes in long distance triathlons, as well as in flat stages of the Tour de France. Adding to its versatility is the AERO+ concept developed in cooperation with Swiss Side: it is the category leader when it comes to low drag numbers but at the same time it is easy to handle in every wind situation. Hubs equipped with SINC Ceramic bearings and ultra-lightweight components throughout are there to make you roll smooth and fast, no matter if you’re fighting against the wind on your time trial bike or trying to escape the bunch on the final meters to the line.

ARC 1100 DICUT® 48
ARC 1100 DICUT® 48

The punchers wheel: the medium profile aero rim, partly bladed spokes and its lightweight build make it easy to flow with the pack and launch your punchy attack when the time is right. Even in harshest weather conditions the ARC 1100 DICUT® 48 will lead you rapidly to the line. Combining our carbon know-how with Swiss Sides leading aero knowledge, this wheel epitomizes lightweight and low drag. The aero hub design featuring straight pull nail head spokes and SINC Ceramic bearings make it stiff and smooth rolling, just right to surprise the lead out train.

Aerodynamics

The
Aerodynamics

The truth is lying on the road…or in the wind tunnel when speaking about our ARC 1100 DICUT® wheels. Check out the results from our tests to find out why these wheels will bring you faster to the finish line than any other wheelset. To make sure that everybody gets our point when speaking about aerodynamics here are some basic definitions of aero terms.

Drag
The longitudinal aerodynamic force slowing the rider down.
Side force
The lateral aerodynamic force pushing the rider to the side.
Yaw
The angle of the oncoming airflow on the rider.
Stall
When the oncoming airflow angle is too high, the airflow can no longer hold onto the surface and the flow will detach. Once stall occurs, drag increases significantly.
Sailing effect
The drag reduction which occurs with increasing yaw angles. Wheels & bike act like a sailing boat sail and push the bike forwards, reducing drag.
Negative drag
The sailing effect is most significant on the wheels and good deep profile aero wheels can produce more forward thrust than drag, so they actually push the bike for wards. This is the same principle as with a sailing boat.

The
Results

ARC 1100 DICUT® 80
Here comes the proof that the ARC 1100 DICUT® 80 is clearly made to go flat out fast. A super low base drag level of only 13.9 watt at 0° yaw angle and negative drag numbers at yaw angles from 12° until stall transfer right into free speed out on the road. The linear steering moment curve without sudden drop-off at the stall point, shows the predictable handling characteristics of the wheelset, supporting the rider to stay in the aero position and pushing the pedal to the metal.

ARC 1100 DICUT® 80 // ARC 1100 DICUT® 62 // ARC 1100 DICUT® 48
No matter which rim depth you prefer, the ARC 1100 DICUT® line up with its three rim depths gives you the perfect option depending on your demand. Independent of the rim depth all wheels have a very low base drag level with a delta of only 0.4 watt at 0° yaw angle. The ARC 1100 DICUT® 62 & the ARC 1100 DICUT® 80 even create negative drag and show the desired sailing effect at higher yaw angles above 12°. The ARC 1100 DICUT® 48 is the perfect wheel for gusty wind conditions creating very low steering moment at higher yaw angles and having a smooth and predictable stall behavior.

ARC 1100 DICUT® 48 RB // ARC 1100 DICUT® 48 DB
There is a lot of discussion on the influence of disc brakes on aerodynamics. Here are the true facts. The disc brake versions of our ARC 1100 DICUT® have a slightly higher base drag level of around two watt. This simply comes from the unavoidable larger hub necessary for disc brakes. The aerodynamic behavior of the wheels is however unaffected. The drag curve and the steering moment behavior show the same ideal characteristics making sure that the rider on a disc brake bike can stay as aero as his rivals on non-disc bikes while enjoying the huge advantage of an easy to modulate and safe braking system.

A new definition of drag

A new
definition of drag

Aerodynamics are probably the number one issue when it comes to road cycling developments at the moment. How can aerodynamic drag be reduced and what does it really mean to reduce drag? What is the actual enhancement for the rider out there on the road? How can wheels influence the aerodynamics of the rider and his bike? Those are the questions we frequently ask ourselves during the ongoing aero development process with our partner Swiss Side. When it comes to the optimization of wheelsets there is still a lot of potential contrary to popular opinion. While everybody is speaking about the optimization of the rim shape we had a look on all the components of the wheelset and their influence on aerodynamic performance. The result is a complete new definition of drag!

Translational drag...

<b>Translational drag...</b>

is what we are traditionally talking about when referring to “DRAG” and what is measured in wind tunnels… until now. Translational drag is the aerodynamic force in the biking direction slowing the rider down. To minimize this translational drag, the complete bike and rider should be as streamlined as possible. As drag power increases exponentially with the speed, from 15km/h the aerodynamic drag is the biggest resistance the rider has to overcome. No news for the moment, as this is basic aero knowledge and almost everybody has been testing in the wind tunnel for reducing drag. But this is only half the truth. There is another very important component of drag...

Rotational drag

<b>Rotational drag</b>

Riding at any given speed the whole bike and rider are moving forward at this speed. As a matter of fact the wheels are moving at this speed too but they are also rotating whilst doing so. They are subjected to the translational drag and something more called: rotational drag. Rotational drag can be described as the additional friction that occurs between the wheel as it passes through its surrounding medium – the air. Whilst the rider and the other parts of the bike face the translational drag only, the wheels are facing both components – translational & rotational drag. In wind tunnel testing and in all wind tunnel published data, the rotational drag is not considered, because the wheels are driven by rollers. So the power required to rotate the wheels is not calculated in the total ‘real world’ drag. Therefore considering translational drag as well as rotational drag is key when it comes to the aero-optimization of wheels.

Knowing that up to 25% of the overall wheel drag can be contributed to the rotational drag, it is one of the most underrated factors in the aerodynamic optimization of wheelsets

1 2 3 4

Measure
rotational drag

To actually measure the influence of rotational drag on a wheelset our engineering crew developed a complete new mobile test rig, which has been integrated into the wind tunnel fixture. Bearing friction is excluded from the measurements by relocating the bearings from the hub into the testing rig. The measuring wheel gets driven manually up to a speed of over 60 km/h. Through a light barrier the decline in speed of the wheel is measured. The rotational energy can then be calculated through the decline of speed and the inertia moment of the wheels, to the highest possible measurement precision.

  1. Drive & Measuring wheel

  2. Oversize axle

  3. External bearings inside of the test rig

  4. Light barrier

The results

1. Rotational drag makes up 25 % of the complete wheel drag.

measured on the ARC 1100 DICUT® 80 DB with a
Continental GP4000S 25c

2. Deeper wheels create less rotational drag.

3. Tire width has a small influence on the rotational drag.

4. Internal nipples create less rotational drag than external nipples.

1
  1. nipples rotate at high speeds
    (high impact on rotational drag)

The potential of spokes

As you can probably guess by now, spokes do have an enormous potential for rotational drag optimization. The difference between standard round spokes (DT Champion) and bladed aero spokes (DT Aerolite) adds up to another 1.5 watt or almost 12 % of drag reduction on the wheel. Time to go a bit more into the technical details.

The <b>potential of spokes</b>

Instantaneous center of rotation
The point of contact from the wheel with the road, where speed is zero, unless there is tire slip. The further away a point in the wheel is from the instantaneous center of rotation, the proportionally larger its speed. Therefore, the point at the top of the wheel moves in the same direction as the center of the wheel, but twice as fast, since it is twice the distance away from the instantaneous center of rotation.

Positive speed
Spokes are moving forward in the direction of their “leading edge” with the air flowing from the front over. All points on the spokes are moving forward at positive speed.

Negative speed
Spokes are moving forward in the direction of their “trailing edge” with the air flowing from the rear over. All points on the spokes are moving forward at negative speed.

1 2 3 Instantaneous center of rotation
  1. rider speed x2

  2. rider speed

  3. instantaneous center of rotation speed = zero

Looking at a full rotation

The ideal spoke

The part of the spokes closer to the rim experiences high positive speeds – being far away from the instantaneous center of rotation - and low negative speeds – being closer to the instantaneous center of rotation. That part of the spokes closer to the hub experiences low to medium positive & negative speeds as the distance from the instantaneous center of rotation stays within a smaller radius.

1 2 Instantaneous center of rotation
  1. SYMMETRIC ELLIPTICAL SECTION

    SYMMETRIC ELLIPTICAL SECTION

    where medium positive & negative speeds occur
    (part of the spoke closer to the hub)

  2. DIRECTIONAL AIRFOIL SECTION

    DIRECTIONAL AIRFOIL SECTION

    where high positive speeds & low negative speeds occur
    (part of the spoke closer to the rim)

The future

Some of these new findings from our R&D have directly influenced the development of the ARC 1100 DICUT® wheels. For example the decision to build up these wheels with internal nipples instead of using external nipples like most of our competitors do. Other findings, like the influence of spokes, are yet to be transferred into the wheel development. It shows the great potential of the ARC 1100 DICUT® wheels to support you out there on the road. Because in the end every watt counts in the real world and all the small details accumulate to one thing: additional free speed for you!

The wheels

ARC 1100 DICUT 80
ARC 1100 DICUT® 80
Technical specifications
ARC 1100 DICUT 62
ARC 1100 DICUT® 62
Technical specifications
ARC 1100 DICUT 48
ARC 1100 DICUT® 48
Technical specifications

#Flatoutfast