How to Choose the Right Size Bike Inner Tube

Intro

Choosing the right inner tube for your bike can be confusing, especially with the different tyre sizing systems in use today. Whether you’re replacing a punctured tube or upgrading to a more suitable one, understanding tyre sizes is essential to ensure a proper fit. This guide will walk you through the three main sizing systems—Metric, Imperial, and ETRTO—so you can confidently select the right tube for your bike.

Bicycle Tubes

Understanding the difference between Inner Tubes Sizing and Tyre Sizing

While tyre sizing remains strict, inner tubes are often more flexible and can fit a range of tyre sizes. This is because inner tubes are made from elastic rubber, allowing them to expand or contract within a certain range. When selecting an inner tube, look at the range of sizes advertised on that specific product listing – it will indicate the range of tyre sizes the tube is designed to fit. As long as your tyre size falls within this range, the tube will fit.

The Four Golden Rules You Must Get Right

1. Choose the Correct Diameter

Your inner tube must match the tyre’s diameter. This is the first number printed on the tyre sidewall (e.g., 700 in 700x25C or 29 in 29×2.25). Using a tube with the wrong diameter will make installation impossible or unreliable.

2. Choose the Appropriate Width

Inner tubes are flexible and can fit a range of tyre widths, but staying within the recommended range is important. A tube that’s too narrow will overstretch and weaken, increasing the risk of punctures. A tube that’s too wide may bunch up inside the tyre, leading to uneven inflation and potential failure. Always check the second number on your tyre sidewall to ensure compatibility.

3. Choose Your Preferred Valve Type

Inner tubes come with different valve types, primarily Schrader and Presta. Your rim must be compatible with the valve type—Presta valves require a smaller hole, while Schrader valves are wider. If you’re unsure which valve type you need, refer to our dedicated guide on choosing the right valve.

4. Choose Your Preferred Tube Type

Tubes come in different materials, including standard butyl, lightweight TPU, and thorn-resistant options. Each has its advantages, but this guide focuses only on getting the sizing right. If you’re unsure which tube type suits your riding style, we have a separate guide covering the differences.

Identifying Your Tyre Size

Before selecting an inner tube, it’s crucial to determine your tyre size. Inner tubes are designed to fit specific tyre sizes, so identifying your tyre size ensures compatibility. Most bicycle tyres have three different sizing systems printed on the sidewall:

    • Metric (e.g., 700 x 23C)
    • Imperial (e.g., 29 x 2.10)
    • ETRTO (e.g., 23-622)

So go right ahead, find the size printed on your tyre sidewall – we’ll use that as the basis for finding the correct inner tube size.

Understanding the Metric Bicycle Tyre Size System

Tyre Size Explanation (700 x 23)

The metric system, commonly used in Australia, is represented by measurements such as 700 x 23C.

    • The first number (e.g., 700) is expressed in millimetres (mm) and represents the approximate overall diameter of the tyre when inflated to a specific pressure on a particular rim width.
    • The second number (e.g., 23) is expressed in millimetres (mm) and represents the approximate width of the tyre when inflated to a specific pressure on a particular rim width.

The problem:

These measurements are often inaccurate due to variations in rim width, tyre pressure, and manufacturer differences. Despite these inconsistencies, it remains a widely accepted sizing method.

Understanding the Imperial Bicycle Tyre Size System

Tyre Size Explanation
Tyre Size Explanation

Some cyclists are more familiar with the imperial system, which is often used for mountain and city bike tyres. In the imperial system, tyre sizes are given in inches, such as 29 x 2.10.

When there are two numbers:

    • The first number (e.g., 29) represents the tyre’s overall diameter in inches, including the tyre itself, when inflated to a given pressure. However, this measurement does not correspond to the rim’s seat diameter, leading to potential confusion.
    • The second number (e.g., 2.10) indicates the tyre width in inches when mounted on the rim and inflated to a given pressure.

When there are three numbers:

Imperial sizes may also include three numbers, such as 22 x 1-3/8 x 1 1/4:

    • The first number (e.g., 22) represents the overall tyre diameter in inches, including the tyre itself, when inflated to a given pressure. However, this measurement does not correspond to the rim’s seat diameter, leading to potential confusion.
    • The second number (e.g., 1 3/8) indicates the tyre height in inches when inflated to a given pressure.
    • The third number (e.g., 1 1/4) represents the tyre width in inches when inflated to a given pressure.

The problem:

These measurements are often inaccurate due to variations in rim width, tyre pressure, and manufacturer differences. Despite these inconsistencies, it remains a widely accepted sizing method.

Understanding the ETRTO Bicycle Tyre Size System

Tyre Size Explanation

The ETRTO (European Tyre and Rim Technical Organisation) system provides the most precise and reliable measurement. For example, in 23-622:

    • The first number (23) represents the tyre width in millimetres.
    • The second number (622) refers to the rim seat diameter, also in millimetres.

The ETRTO system eliminates confusion by providing exact internal dimensions rather than external approximations. While it may be the least used system for consumer tyre selection, at Mr Cycling World we consider it the gold standard for ensuring compatibility.

What Happens if You Use the Wrong Tube Size?

If you use a tube that is slightly too small, it will stretch when inflated, making it more prone to punctures. If a tube is too large, it may fold inside the tyre, increasing the risk of failure.

In an emergency repair situation, an incorrectly sized tube might get you home, but it should not be relied upon for long-term use. Always aim to use the correct tube size to ensure optimal performance and safety.

Conclusion

Congratulations on understanding bicycle tube sizing! We know this can be a confusing topic, but we are experts in our field and are here to help. If you’re still unsure, don’t hesitate to contact us—we’d prefer to get it right the first time!