Do Not Equip Your Road Bike with Tires That Are Too Narrow
The impact of tire width on road cycling performance has always been a topic of great interest among cyclists. A few years ago, it was generally believed that narrower tires had better aerodynamic performance due to their smaller volume. Additionally, the smaller contact area with the ground theoretically resulted in lower rolling resistance. For a long time, even professional road racers held this belief.
With technological advancements and improved testing methods, it has been discovered that slightly wider tires not only offer better aerodynamic performance but also come with lower rolling resistance and improved comfort. Since around 2020, more professional road cycling teams have been moving away from 23c tires in favor of 25c and 28c tires, and sometimes even 30c tires on gravel roads. This shift clearly demonstrates that wider tires outperform the previously more commonly used narrower tires of less than 23mm.
Why 25c & 28c Perform Better Than 23c in Road Cycling?
It seems counter-intuitive, but it is indeed true. Wouldn’t wider tires have a larger frontal area and therefore more wind resistance? The reason lies in the combination of wider tires with wider rims. This combination creates a fatter elliptical cross-sectional profile. If you use 23c or narrower tires, the combined cross-sectional profile is a flatter ellipse. In crosswind conditions, a fatter elliptical profile offers better aerodynamic performance. Of course, this requires the use of wider rims as well.
Rolling Resistance
Previously, we believed that narrower tires had lower rolling resistance. With advances in testing technology, we’ve found this is not true. Although wider tires have a greater contact width with the ground, their contact length is shorter. This means that in the direction of travel, the contact length between the tire and the ground is reduced, thereby lowering rolling resistance.
Comfort
On the other hand, wider tires can hold more air, allowing for greater deformation when impacted. When riding over rough surfaces, the tire inevitably encounters opposing forces from the ground. At this moment, greater deformation absorbs the impact. Under suitable conditions, wider tires not only have lower rolling resistance in the direction of travel but also offer better comfort.
Why Not Choose Tires Wider Than 30c?
This is a good question. In general, after a certain width, the diminishing returns in reduced rolling resistance, wind resistance, and increased comfort become very small. However, the increase in cost and weight is unavoidable. Additionally, considering compatibility with other bicycle parts, extensive experimental data suggests that 25c and 28c tires are currently the optimal choices. Unless you have compelling reasons, avoid choosing 23c or 30c tires. Riders using narrow rims and lighter riders can use 25c tires. If you are heavier or plan to ride on rougher roads, you can opt for 28c tires.
For the Lowest Rolling Resistance
In one test, the Continental Grand Prix 4000s II (28mm) outperformed other brands’ 28mm tires and even the same brand’s 25c tires, offering the lowest rolling resistance.
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