When it comes to riding a bike, the wheels and tires are a major factor affecting your speed. However, tubeless tires and rims can be a game-changer in this regard. With advancements in technology, tubeless setups have become the fastest road tire and wheel combination available. If you choose the perfect tubeless tire, wheel, and pressure combination, you can gain some extra speed without exerting any additional effort.
Rolling Resistance
Rolling resistance is mostly caused by the friction that occurs when a wheel rolls over the road. A wider tire has less rolling resistance than a narrow tire because it has a shorter, wider, and rounder contact patch, which rolls more easily than the longer, slimmer, elliptical shape of a narrower tire that deforms more as it rolls. Wider tires can also be run with lower pressures, making them absorb bumps from the road without losing as much momentum. However, to reap the benefits of running wider tires, they need to be mounted on wider rims to maximize speed and efficiency. When a tire is not mounted as firmly as possible on the rim, micro-movements of the rubber on the rim can add up to significant energy losses. Therefore, a 25-mm or 28-mm tire will sit more firmly on a wider rim.
Aerodynamic Drag
As the speed of an object increases, the aerodynamic drag it experiences increases exponentially. This means that it takes more than eight times as much power to go twice as fast relative to the air. Since the power of the rider is limited, achieving higher speeds without increasing power output requires improving the object's aerodynamic shape as it moves through the air. When the rim shape is designed effectively, you can greatly reduce the resultant drag in the wheel and keep it stable.
Lately, there has been a growing trend of using wider tyres on bikes. When it comes to aerodynamics, the width of the rear tyre does not have much effect. However, the width of the front tyre is more impactful. Hence, it is recommended to use a 23mm front tyre, regardless of whether the wheel is designed for 25mm tyres. While riding at speeds above 30km/h, 23mm tyres have greater aerodynamic benefits than 25mm front tyres.
Photo: Courtesy ENVE
Why Choose Tubeless Tire
Tubeless tires are safer to run at lower pressure compared to tubed tires as there is no tube to get pinched when hitting sharp bumps, which reduces rolling resistance on uneven roads. Furthermore, tubeless tires have lower rolling resistance as they eliminate the inner tube's hysteresis and its friction against the inner tire casing. The first generation of tubeless road tires were airtight and did not require sealant, but they had so much rubber coating on their insides that their weight was the same as a comparable tire and tube, and the frictional rolling losses were similar. However, modern tubeless-ready tires with sealant are lighter and have lower rolling resistance than tubed tires.
Hooked Rims vs. Hookless Rims
Rims with hooked rims have a noticeable inward-facing hook or flange on the inner edge of the rim sidewall. This hook serves to secure the tire bead in place and prevent it from detaching from the rim, particularly at high pressures. In the past, most rims were built with hooks to accommodate clincher tires (tires with inner tubes), as the hook provided a dependable mechanical grip.
A hookless rim is a type of wheel that doesn't have a hook or flange on the inner edge of the rim. Instead, it has a straight sidewall profile with no inward-facing hook. The tire bead relies on a precise fit and air pressure to securely engage with the rim. Hookless rims are generally used in tubeless setups, where the tire forms an airtight seal against the rim bed without an inner tube.
While hookless rims offer better impact resistance and easier installation, hooked rims provide extra mechanical lock and security.
If you ride on smoother roads and prioritize aerodynamic gains, hookless rims may be a suitable choice.
Tire and Rim Width
For individual competitions where time is a crucial factor, we recommend using a 25mm tire in the front and a 28mm tire in the back wheel. The external rim width should be at least 1mm wider than the tire used in the front. Choosing a 25mm tire for the front can help reduce the aerodynamic drag on most aero rims with an internal width ranging from 19 to 22mm. Using a wider 28mm tire for the rear wheel doesn't have any negative impact on aerodynamics since it is covered by the frame. Additionally, it helps save some watts of rolling resistance and provides better traction.
To achieve the best performance, athletes are advised to use tubeless clincher tires with low rolling resistance. The tire should be used on a rim that is approximately 5% wider than the tire. However, as the size of both the tire and rim increases, the need for a wider rim decreases. This is because the larger radius of the tire allows the air to attach to the rim more easily when exposed to yaw.
The Fastest Setup
Firstly, tubeless tires are a better choice than tubular tires. They have lower rolling resistance and provide a smoother transition to the rim, especially with hookless rims. This results in better aerodynamics.
Secondly, optimizing the rim and tire width can double your performance. For optimal aerodynamic performance, use 27-30mm (outside width) rims with 25-26mm wide tires on the front. Remember to mount the tire on the rim before measuring, as the tire markings are only a guide. Use 25-28mm wide tubeless tires on the rear wheels on the same width rims. If you're using hookless rims, you'll experience even better aerodynamics.