AC2:1 and AA2:1 concepts
2:1
 We use a special spoking for our rear wheels.
Because of the multi-speed drive-trains, the rear wheels do not have the same bracing angle on the two sides. Keeping the rim centered between the frame dropouts involves a much higher spoke tension of the drive side, where the bracing angle is the smallest. Because of this asymetry, the rear wheels are very unbalanced, both in term of tensions and in term of stiffness. The lack of spoke tension on the non-drive side increases the spokes fatigue, thus their failures. Our hub is designed to compensate these weaknesses.
Our special spoking 16:8, 16 drive side spokes and 8 non drive side spokes, laced to our hub with a specific geometry, balances the tensions on the two sides of the rear wheel.
Thus, while a traditionnal rear wheel has about 100% of tension on the drive side, and from 40 to 60% on the non drive side, our rear wheels are balanced: 100%/100%. Through this spoking, the torque transfer also is better:
- the drive side spokes are perfectly tangent to the hub and transfer the torque in the best conditions
- the number of drive side spokes transfering the rider output is 33% higher than a wheel laced with the traditionnal 12/12 method.
- the large drive side flange increases the lever arm the spokes can pull to transfer the torque
AC and AA
The shallow wheels are the most exposed to lateral stiffness drops under heavy loads. The tests we have driven confirmed our original idea, to know, lacing these wheels with 8 thicker and stiffer spokes on the non drive side, to compensate the reduction of spokes.
This feature makes our low depth wheels laterally stiff and stable, even for the stronger riders. The rim does not move between the brake pads, even when delivering the most power during a sprint.
Our aero wheels get the same spokes (bladed, thin, aero) on the two sides of the rear wheels. Indeed the stiffness of the rim and its short spokes do not require the AC2:1 concept.
AC2:1
| AA2:1
| | Drive side spokes | Non drive side spokes | Drive side spokes
| Non drive side spokes | 16 x DT Swiss Aerolite
| 8 x DT Swiss Competition
| 16 x DT Swiss Aerolite | 8 x DT Swiss Aerolite
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AC: Drive side/non drive side: DT Swiss Aerolite spokes / DT Swiss Competition spokes. Tempo and Svelt receive this spoking.
AA: Drive side/non drive side: DT Swiss Aerolite spokes / DT Swiss Aerolite spokes. Optimal and Magnum receive this spoking.  We highlighted the non drive side spokes on the drawing above. All the spokes are black on the real wheels. Detailled explanations The stiffness of a wheel depends on several parameters, whose the support of the rim on the hub. This support forms a "triangle" with the spokes that is called the bracing angle. This is directly related to the distance between the hub flanges, and it plays one of the biggest role in overall wheel lateral stiffness.
The front wheels have symetric and wide bracing angles, bringing stability and lateral stiffness.
Problem Nowadays, the rear wheels suffer of a major drawback coming from the slow evolution of our bicycles. Two parameters slowly weakened our rear wheels:
- the frame dropouts distance is 130mm for Shimano or 131mm for Campagnolo
- the multi speed drive-trains increased the length of the hub rotor with the time So to leave some place for the cassettes, the drive side hub flange width had to be reduced (distance "d" on the drawing below). The rear wheels were then weakened on two different points. | 
| First, from a lateral stiffness point of view: the non drive side of the wheel is stiffer than the drive side, this asymetry reduces the performance of the wheel.
Second, from a spoke tension point of view: keeping the rim centered between the frame dropouts involves a higher spoke tension on the drive side than on the non drive side. It leads to low tensions on the non drive side, meaning a drop in performance too. The centering of the wheel between the frame dropouts follows this rule:
P1.R1.T1 = P2.R2.T2 P are the bracing angles of the two sides (distances "d" and "2d" on the drawing), R is the number of spokes, and T the spoke tensions. | Solutions Several solutions have been found to balance the two weaknesses: 1) reducing the non drive side bracing angle (distance "2d"). This solution reduces the spoke tension differences but significantly decreases the lateral stiffness of the wheel as the distance between the flanges is shorter.
2) reducing the number of spokes (R1), where the spoke tension is the lowest: on the non drive side. This solution balances the spoke tensions but reduces the non drive side wheel stiffness.
3) using thicker and stiffer spokes where the wheel is the weakest: on the drive side. This solution balances partially the two sides stiffnes, but does not play a role for balancing the spoke tension. It also comes with a certain weight rise.
4) using an off-centered rim reduces the non drive side bracing angle (distance "2d"), and increases the drive side bracing angle (d). This solution is good for balancing both the tension and stiffness, but it's only a patch.
5) using a radial drive side spoking, and crossed non drive side spoking slightly balances stiffness as the drive side - the weakest - receives smallest spokes that bend less. It's a small patch here too. These five solutions are good to cut one of the weakness, but they always peedle the second. Our RAR double solution Our wheels are balanced both in term of tension and stiffness thanks to the following points: - our rear hub is specific, the distance between the center and the flanges is twice as big on the non drive ("2d") than on the drive side ("d")
- the 2:1 spoking, associated to this hub makes the spoke tensions perfectly balanced on the two sides
- our low depth wheels receive thicker and stiffer spokes (2.0/1.8) on the non drive side to make them laterally as stiff as possible.
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