In recent years, cycling has seen a noticeable shift towards wider road tyres, moving from the traditional 23mm to a more substantial 28mm and now venturing into the realms of 30mm and beyond. At the upcoming Paris-Roubaix event, some professional riders are even experimenting with 35mm tyres—tyres that would have disqualified them in cyclocross events just a few years ago due to their size.

The burning question now is, will we reach a point where elite cyclists like Tadej Pogačar and Jonas Vingegaard will be racing on 40mm or even 50mm road tyres? Or should we skip ahead and start implementing them now?

Pirelli has taken a considerable step in this direction, recently launching its P-Zero Race TLR range available in widths from 26mm to an impressive 40mm. But what really matters? It's widely known that wider tyres generally reduce rolling resistance—which means they make pedaling easier. However, the larger size also brings aerodynamic concerns that could negatively impact speed. The key question is whether the rolling resistance benefits of wider tyres outweigh the aerodynamic drawbacks.

To tackle these questions, a rigorous study was conducted at the Silverstone Sports Engineering Hub, utilizing both a Pedalling Efficiency Rig for rolling resistance and a Wind Tunnel for aerodynamics testing.

Rolling Resistance Testing: What You Need to Know

The Pedalling Efficiency Rig is designed to simulate real-world riding conditions and measure the total wattage loss in the system, allowing researchers to clearly define how much power is lost due to each tyre's rolling resistance. A series of tests were carried out, maintaining uniform conditions while only changing the tyre width, revealing critical data.

The results were striking: wider tyres exhibited significantly lower rolling resistance on rough surfaces like cobbles compared to their narrower counterparts—showing a whopping difference of 65.7 watts at higher speeds when moving from a 26mm to a 40mm tyre on a gravel-specific rim. This indicates that when it comes to navigating rough terrains, wider tyres can provide significant performance benefits.

Aerodynamic Testing: The Other Side of the Coin

The Wind Tunnel testing provided insights into aerodynamics, measuring how different tyres and widths affect drag. Surprisingly, it revealed that narrow tyres generally offered less drag, thanks to their smaller frontal area. The data suggested that while wider tyres improve handling and comfort on rough surfaces, they do carry an aerodynamic cost that becomes more apparent at higher speeds.

For example, when switching from a 26mm to a 40mm tyre, the drag increased by about 10.47 watts at higher speeds—leading to a net negative effect in terms of aerodynamic efficiency. This serves as a critical consideration for racers who rely on speed above all else.

The Future of Cycling: Could 40mm Tyres Become the Norm?

Given the findings, the age-old debate surrounding tyre widths heats up—a wider tyre may not be the ultimate choice for smooth roads, but on cobblestones and rough surfaces, the advantages are clear. As cycling develops, there is a profound case to be made for adopting wider tyres in future bike designs.

Currently, the cycling industry lacks the necessary design adjustments to optimize aerodynamics for these expansive tyres fully. The future may see bikes built with wider clearances—resulting in a seamless integration of 40mm tyres without the substantial aerodynamic penalties currently observed.

As for everyday cyclists, the recommendations are simple: opt for the widest tyre that fits comfortably within your bike’s infrastructure. This change can help with overall comfort, control, and performance across various terrains, particularly in the varied conditions many of us experience daily.

Conclusion: A New Era of Cycling?

Will tomorrow's cyclists be racing on 40mm tyres? While the current generation of road bikes isn't fully equipped to handle such sizes, it’s apparent that the evolution of bike design will likely embrace wider tyres for all riders over time. Whether you’re a casual weekend rider or a competitive racer, investing in the latest generation of tyres may ease the strain on your body and enhance your overall riding experience. Don't wait for the change—embrace it now and redefine your ride!