Aerodynamic wheels first entered the bicycle industry over 30 years ago. While the early models did provide an aerodynamic benefit, they were often cumbersome, fragile and could be difficult to handle. Since their introduction, significant improvements have been made. Today, in addition to the airflow benefits, most aerodynamic wheels are strong, stiff and offer significantly improved handling.
Knight Wheels was started with the goal of developing the most aerodynamic wheels on the market. When our engineering team was first charged with this task, they began by studying several of the leading aerodynamic wheels available today. The aero performance of the wheels were measured both in the wind tunnel as well as on the road under real-world conditions.
Our testing inferred that the majority of aero wheels available place the design focus on the leading edge – the tire and rim’s outer edge. At first blush, this makes a lot of sense since research has proven that the frontal area has a significant impact on the overall aero performance.
When our engineering team began the design process for Knight Wheels the decision was made to look at the wheel not in isolation, as most manufacturers do, but rather as part of the bicycle system. As our engineers worked through the process, the data revealed that while the leading edge of the wheel should not be ignored, designing around the trailing edge could offer a far greater aerodynamic benefit – this lead to the development of Trailing Edge Aerodynamic Manipulation Technology (TEAM Tech). TEAM Tech focuses on how the air flows from the tire, to the rim, back to the tire, and ultimately to the down tube and the rest of the frame.
The result of our engineers’ knowledge, industry leading experience and hard work, are a selection of wheels designed to offer you superior aerodynamic benefit regardless of riding conditions. Whether you are trying to set a new Personal Best in a race, or leading the charge in the town line sprint, Knight Wheels are engineered to give you an aerodynamic edge.
The proprietary shapes of our rims are a direct result of designing the wheel as part of the bicycle system (tire, rim, fork, frame). Once the test data confirmed that the system design approach would result in superior overall performance, our engineers began experimenting with rim shapes.
As previously mentioned, aerodynamic wheels have evolved tremendously since they first entered the bicycle industry. When manufacturers first started designing aero wheels, they began with a sharp “V” shape. While this shape gave the appearance of speed, they offered little aero benefit, and were quite unstable. Rim manufacturers continued designing and testing shapes with some deciding that a more rounded, blunt “U” shape may be a better option. While this updated shape does have its limitations, testing revealed that the flatter shape not only improved the handling, but the aero performance as well.
When the design process began at Knight Wheels, our engineers started with a wide array of shapes. Each shape was designed, tested and refined with the focus being the trailing edge of the rim. The more tests we conducted, the clearer it became that a parabolic shape (not as sharp as a V, but a more gradual width increase than a U) best suited our needs.
Once the idea of a refined parabolic shape was agreed to, our engineering team continued to enhance it. Using the tools at their disposal, including Computational Fluid Dynamics (CFD) and several wind tunnels, the Knight Wheels engineers started with a NACA (National Advisory Committee for Aeronautics, now known as NASA) airfoil-based shape and reworked it to better meet our goals. The final result is an elongated parabolic shape, with an arc that was manipulated based on our testing.
In aerodynamic terms there are three different types of airflow. The most desirable is laminar flow, which means the air remains attached to the surface of the rim and other elements of the bicycle system for as long as possible. Testing in the wind tunnel revealed that the airflow passes over a V shape with minimal attachment, and has to overcome an abrupt transition at the blunt edge of a U shape. The Knight Wheel rim shape is engineered to offer a more gradual wrapping of the airflow around the rim, resulting in smoother, more attached flow. With each turn of the pedal, the rider battles airflow. By engineering a more aerodynamic shape, Knight Wheels reduces the drag resulting in a more efficient ride.
Since first being introduced to the market, carbon wheel braking has been a major concern with consumers. Despite the numerous advancements that have been made over the years, the thought of poor braking performance is still a significant reason many people will not make the switch to full-carbon wheels.
The challenge with the braking system on a carbon rim is a result of the carbon material itself. When the brakes are applied, the caliber is closed, and the brake pads press against the rim to slow it down. The pad rubbing along the rim creates friction, and that friction creates heat – under extreme braking conditions, a significant amount of heat can be produced. If this potential heat is not considered during the design phase, the adhesives that hold the carbon fiber together can breakdown. The result is the rim begins to separate along the braking track until the eventual point of failure.
To address this concern, our engineering team took the approach to overbuild our carbon structure at the brake track. Most carbon rims on the market have a wall thickness of 1.5mm at the brake track; Knight Wheels are designed with 3mm of thickness. While this thicker section of carbon adds a bit of weight to the rim, it also adds significant heat-resistance as well. Under braking load, the heat has more carbon material in which to dissipate, allowing temperatures to stay cooler, and the adhesives to stay strong.
Manufacturing a wheel that is aerodynamically superior is the goal of Knight Wheels, however, safety is also a key concern. Each of our rims must meet our rigorous standards, which we believe surpass those of the cycling industry. Case in point, some of our competitors’ wheels repeatedly failed our testing protocol at 1/3 of our standards. While these self-imposed requirements add some weight to the rims, and increase our design time, it also ensures the safety of each rider that puts their trust in Knight Wheels.
Not all carbon fibers are created equal, and we choose Toray of Japan’s Torayca® brand fibers. Toray Industries is the unequivocal global leader in the carbon fiber industry, and as such is the world’s number one supplier of carbon fibers for aerospace applications, including Boeing’s 787 Dreamliner and the Airbus A350; Lockheed Martin’s F-35 Lightning II fighter jet, the International Space Station, satellites and rocket casings.
When most cyclists think hubs their first thought is DT Swiss. No name in the hub industry carries such an outstanding reputation for quality, consistency, durability and serviceability. Naturally we chose DT as the source for all our hubs, spokes and nipples to further bolster the already meticulous and rigorous standards by which we manufacture our rims.
When choosing the specific hub, we selected the renowned 240s hubs for all of our models. While not the lightest on the market, 240s are an extremely durable, race-ready hub that performs equally well in crits, centuries or a weekend ride. They feature the legendary Star Ratchet System drive mechanism – a simple system of two alloy “gears” ratcheting together in smooth, precise action, with an easy-to-service and highly compatible press fit design.
Using lighter weight bearings, axle and shell than most DT hubs, the 240s is only manufactured in one Swiss shop to ensure consistency. And their modular design allows for easy, tool-free servicing and end-cap swapping for added convenience.
Sapim’s CX-Ray spoke still turns in the best results in fatigue testing of any spoke in its class. Its unique strength and flexibility makes the CX-Ray suitable for most bicycle disciplines and as such are used by top bike racers and triathletes around the world. Even downhillers use them, recognizing their strength and flexibility. Special alloy treatment and sophisticated production make this all possible.
- Almost as light as Titanium
- More long lasting than any other spokes on the market.- extremely high fatigue test results
- Special alloy treatment and sophisticated production
- The best aerodynamic spoke available
- Produced from high-tensile, fatigue-resistant 18/8 stainless steel conforming to the Sapim quality standard specifications.
Once the decision had been made to utilize the CX Ray spokes, our engineering team needed to decide which format – J-Bend or Straight-Pull – best suited our needs. Each spoke format has its benefits and limitations.
- J-Blend spokes are more cost-efficient, but are seen by some as less durable than a Straight-pull spoke, mainly due to the spoke hole interface
- Straight-pull spokes are seen as more durable, but come at a significant price premium
In an effort to keep Knight Wheels rims as affordable as possible, we decided to go with the J-Bend format. But rather than accept the increased potential for breakage, our engineering team was tasked with solving this challenge.
The first step was to review the interaction between the rim and spoke. Most spoke holes are drilled in a straight line toward the center of the hub. This means the spokes have to be angled toward the hub flange, which results in the spoke being exposed to a slight torque as it exits the nipple. With the assistance of a computer-controlled CNC machine, our spoke holes are now drilled at the precise angle at which the spoke exits towards the flange. This small, but important change, alleviates the torque on the spoke resulting in longer life.
In addition to adjusting the hole direction, our engineering team also increased the amount of carbon material around the spoke holes. This additional material increases the strength and minimizes the potential for spoke “pull through,” where tension on the spoke and nipple actually pulls the nipple through the hole, which can potentially damage the rim structure. Our spoke holes are tested to withstand the highest spoke pull-through pressure standards in the industry – far above minimum requirements.
We use only the Pillar Hex 10 made from 7075 aluminum, which is a hexagonal industry standard nipple with a special ‘rounded’ face that allows the spoke to articulate within the spoke hole, resulting in less stress beteen the spoke/rim interface.
Better testing leads to a better wheel
The standard design process for most wheel companies starts with developing and testing a theory, moves to drawing and testing new shapes using Computational Fluid Dynamics (CFD), and then prototyping and testing in a large format wind tunnel. The engineering team at Knight Wheels added a few additional steps to the process to ensure a better product in the end.
The first addition was the use of a small format wind tunnel, before moving to a large format one. Wind tunnels are incredibly useful in helping to determine how a shape will perform under real world conditions. The challenge with a large format tunnel, which most manufacturers use, is that they are designed to test the aero performance of a wide array of products – bobsleds, cars, even scaled to model planes. Because of the space required to test these products, a large wind tunnel needs to move a high volume of air causing additional disturbance, which can skew the results of smaller products such as wheels.
By utilizing a smaller format tunnel, before moving to a larger one, we are able to ensure a higher level of uniformity – which leads to more accurate testing. Given its size, a small tunnel moves less air through a smaller space. The reduced airflow significantly minimizes the number of variables, and allows the wheels to behave in a more real-world setting than in a larger tunnel.
The second step the Knight Wheels engineering team added was the development a custom-made scale. As previously mentioned, large format tunnels are designed with bigger products in mind. This is true for both wind flow as well as the measuring apparatus. To ensure the most accurate testing available, our engineering team developed a custom scale that is capable of measuring significantly smaller amounts of drag with a much higher accuracy.
Finally, once the engineering team was satisfied with their theory and testing process, they turned to the field of academia. Knight Wheels worked with Dr. Phil Lavoie, Associate Professor with a PhD in Aerodynamics, to hone and validate our work throughout the entire research and development phase. By partnering with Dr. Lavoie, it provided an expert third party to review the work, interpret and validate the data and provide additional insight.
Each of these steps allow for improved accuracy in our testing and development. This increase allows us to push the envelope in our design, and provide a better product for our customers.
After braking safety, one of the largest concerns with aero wheels amongst consumers is handling. Aerodynamic rims are designed with varying levels of depths to provide lift, which helps the wheel move through the wind more efficiently. The challenge comes when the wheel is at yaw, and the rider experiences wind steer.
Wind steer occurs when the rider faces airflow above zero degree yaw, resulting in a crosswind. When a crosswind hits a carbon wheel it can force the wheel off of the desired plain. This causes the rider to veer off course, or expend additional energy to maintain the preferred path.
The engineering team at Knight Wheels took the wind steer effect into consideration when designing our wheels. They were able to determine that moving a higher percentage of the aerodynamic lift to the back half of the wheel aided in counteracting the effects of a crosswind. Most wheels are designed with either equal lift, or a higher percentage in the front half of the wheel, which only exasperates the problem.
Reducing the wind steer, not only helps our consumers ride faster, but also gives them the confidence to do so.