When riding a bicycle, the wheels and tires are an important factor that affects speed. However, tubeless tires and rims can play a crucial role in this regard. Thanks to advances in technology, tubeless tires are the fastest tire and rim combination on the road. By choosing the perfect combination of tubeless tires, rims and air pressure, you can gain speed without any additional effort.

rolling resistance

Rolling resistance is primarily caused by the friction created when a wheel rolls across the road. A wider tire has less rolling resistance than a narrow tire because it has a shorter, wider, rounder contact patch that rolls more easily than the longer, slimmer, elliptical shape of a narrower tire, which deforms more as it rolls. Wider tires can also be run at lower pressures, allowing them to absorb bumps in the road without losing as much momentum. However, to take advantage of wider tires, they must be mounted on wider rims to maximize speed and efficiency. If a tire is not as tight as possible on the rim, the micro-movements of the rubber on the rim can add up to significant energy losses. Therefore, a 25 or 28 mm tire sits tighter on a wider rim.

aerodynamic drag

As an object's speed increases, air resistance increases exponentially. This means that more than eight times the power is required to achieve twice the speed relative to the air. Since the driver's power is limited, the aerodynamic shape of the object moving through the air must be improved to achieve higher speeds without increasing power. If the rim shape is designed effectively, one can significantly reduce the resulting drag of the wheel and keep it stable.

Recently, wider tires have been increasingly used for bicycles. In terms of aerodynamics, the width of the rear tire doesn't have much of an impact. However, the width of the front tire is of greater importance. It is therefore recommended to use a 23mm front tire regardless of whether the wheel is designed for 25mm tires. At speeds above 30 km/h, 23 mm tires have greater aerodynamic advantages than 25 mm front tires.

Photo: Courtesy of ENVE

Why tubeless tires

Tubeless tires are safer than tubed tires at lower pressures because the tube cannot be pinched when hitting sharp bumps, reducing rolling resistance on uneven roads. In addition, tubeless tires have lower rolling resistance because the hysteresis of the tube and its friction on the inner tire carcass are eliminated. The first generation of tubeless road tires was airtight and did not require sealant, but had so much rubber coating on the inside that their weight was equivalent to that of a comparable tire with a tube and the rolling losses due to friction were similar. However, modern tubeless tires with sealing material are lighter and have lower rolling resistance than tires with tubes.

Hook rims vs. hookless rims

Hooked rims have a prominent, inward-facing hook or flange on the inside edge of the rim side. This hook is used to secure the tire bead in place and prevent it from coming loose from the rim, especially under high pressure. In the past, most rims were built with hooks to mount clincher tires (tubed tires) because the hook provided a reliable mechanical grip.

A hookless rim is a type of wheel that does not have a hook or flange on the inside 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 the rim. Hookless rims are usually used in tubeless systems, where the tire forms an airtight seal with the rim well without a tube.

While hookless rims offer better impact resistance and easier installation, hooked rims provide additional mechanical support and security.

If you ride on smoother roads and value aerodynamic benefits, hookless rims may be the right choice.

tire and rim width

For individual competitions where time is of the essence, we recommend using a 25mm tire on the front wheel and a 28mm tire on the rear wheel. The outer rim width should be at least 1 mm wider than that of the front tire. Choosing a 25mm tire for the front wheel can reduce drag on most aero rims with an internal width of 19-22mm. Using a wider 28mm tire for the rear wheel has no negative impact on aerodynamics as it is covered by the frame. It also helps save a few watts of rolling resistance and offers better traction.

To achieve the best performance, athletes are recommended 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 the tire and rim increases, the need for a wider rim decreases. This is because the larger radius of the tire makes it easier for air to attach to the rim when exposed to yaw.

The fastest setup

First, tubeless tires are a better choice than tubular tires. They have lower rolling resistance and provide a smoother transition to the rim, especially on hookless rims. This leads to better aerodynamics.

Secondly, by optimizing rim and tire width you can double your performance. For optimal aerodynamic performance, use 27-30mm wide rims (external width) with 25-26mm wide tires at the front. Remember to mount the tire on the rim before measuring as the tire markings are a guide only. Use 25-28mm wide tubeless tires on the rear wheels on rims of the same width. If you use hookless rims you will experience even better aerodynamics.