The Mystery of 'C' in Bicycle Tire Size

Bicycle tire sizing can be confusing, especially for those new to the world of cycling. One term that frequently puzzles riders is the 'C' in '700C' tire sizes. This article delves into the meaning of this letter and provides a comprehensive understanding of what the numbers and letters on your bicycle tires actually represent.

Understanding 700C Tire Sizes

The number 700 in '700C' refers to the nominal diameter of the tire, which is approximately 700 millimeters (mm). However, it is important to note that this is a nominal figure, and the actual diameter may be slightly less. The letter 'C' is a crucial part of this designation and holds a specific meaning in the tire sizing system.

The Significance of the Letter 'C'

The 'C' in '700C' does not stand for centimeters. It is instead a legacy from an older French tire-sizing system. The letter 'C' originally denoted tires that were 'commerciales' (commercial) in nature, used for vehicles carrying heavy loads such as minivans and trucks. However, in the context of bicycle tires, 'C' has a different meaning and significance.

What 'C' Really Means

Sheldon Brown, a renowned expert in bicycle maintenance and tire sizing, explains that in the French system, 'A' represented the narrowest tires, 'D' the widest, and 'C' were the tires that fell in between. Today, the 'C' in '700C' tires indicates a specific inner diameter of 622 mm, which is a crucial measurement for fitting the tire correctly to the rim. This inner diameter is a standard dimension that all '700C' tires share.

Inner Diameter of 622mm

The 'C' in '700C' tires stands for a consistent inner diameter of 622 mm. This is a reliable and dependable feature, making '700C' tires easy to identify and install. The inner diameter is a critical measurement, ensuring that the tire can fit correctly onto the rim and provide the necessary support and balance for a smooth and safe ride.

Nominal vs. Actual Dimensions

Although the outside diameter of '700C' tires is often quoted as 700 mm, this is a nominal figure. The actual diameter may be slightly less. Other tire sizes like 700A, 700B, and 700D have different inner diameters, which can range from 594 mm to 630 mm. However, for practical purposes, '700C' is considered a standard size with a fixed inner diameter.

Why 700C Isn't the Only Option

While '700C' is the most common bicycle tire size, other sizes do exist for different purposes. For example, 650B tires have a nominal outside diameter of around 650 mm, with a different inner diameter. Understanding the differences between these sizes is essential for selecting the right tire for your bicycle and riding conditions.

Conclusion

Understanding the 'C' in '700C' tire sizes is crucial for riders looking to choose the right tire for their bicycle. The 'C' signifies a standard inner diameter of 622 mm, making '700C' tires easy to identify and install. Additionally, familiarity with other tire sizes can help riders make informed decisions based on their specific needs and riding conditions.

Further Reading

To delve deeper into bicycle tire sizing and maintenance, visit the Sheldon Brown's Tire Sizing Page. This extensive resource provides detailed information and valuable insights into the world of bicycle tires.