The Ultimate Guide to Bicycle Tire Markings: Understanding Sizes in 2026

Bicycle tire markings follow three primary systems: ETRTO (e.g., 28-622), Inch (e.g., 29x2.4), and French (e.g., 700x28c). The ETRTO system is the most precise for ensuring rim compatibility, while road cyclists typically use the French system and mountain bikers rely on the Inch system. Always match the numbers on your current sidewall when buying new tires.

Why are Bicycle Tire Sizes So Confusing?

If you have ever looked at the side of your bike tires, you probably saw a string of numbers that looked like a secret code. These markings are essential for safety and performance, yet they vary depending on the type of bike you ride.

Most cyclists stick to the system they are familiar with. Road and gravel bike tires usually display French measurements, while mountain bike tires and 26x4.0 fat bike tires use the Inch system. However, relying solely on inches can lead to mistakes, as not all "26-inch" tires are designed for the same rim diameter.

The Three Main Sizing Systems

To navigate the market effectively, you need to understand how these three systems overlap:

1. ETRTO (European Tyre and Rim Technical Organisation): This is the universal standard. It uses two numbers (e.g., 35-622). The first is the tire width in millimeters, and the second is the internal diameter of the tire (the bead seat diameter).

2. Inch System: Traditional and common in the US. It lists the outer diameter and the width (e.g., 27.5 mountain bike tires might be marked 27.5x2.25).

3. French System: Primarily used for road and gravel. It lists the outer diameter and a letter indicating the width (e.g., 700x35c).

Quick Reference: Tire Size Comparison Table

How to Choose the Right Size for Your Ride

When shopping for road bike tires or MTB rubber, the most reliable method is to find the ETRTO number on your current tire. While "26 inch" is a common search term, there are actually three different rim diameters that can be labeled as 26 inches. Using the ETRTO number (like 559mm or 590mm) ensures the tire actually fits your rim.

• For Speed: Narrower tires (25mm–28mm) reduce aerodynamic drag.

• For Comfort: Wider tires (35mm+) allow for lower PSI, which absorbs road vibrations.

• For Grip: High-volume mountain bike tires (2.4" and up) provide a larger contact patch for off-road traction.

Note: Real‑world speed depends on more than just nominal tire width. Tire pressure, rim width and profile, and the surface you ride on all play a major role in how fast a given setup actually feels and rolls. For example, a slightly wider tire run at an optimised pressure on a modern wide rim can be faster on rough tarmac or gravel than a narrower tire pumped up too hard on a narrow rim, because it reduces vibration losses and maintains better contact with the ground.

Product Spotlight: Fincci Precision Tires

At Fincci, we design our tires to meet the exact standards required by modern cyclists, whether you are commuting or hitting the trails. Our catalog covers everything from high-pressure road slicks to high-volume 26 inch bike tires.

Technical Specs & Features:

• High TPI (Threads Per Inch): Increases casing flexibility for a smoother ride.

• Optimized PSI Ranges: Clearly marked on every sidewall to help you find the balance between speed and grip.

• Versatile Sizing: We offer a full range of sizes, including 700x28, 700x35, 700x45, 29x2.4 etc.

The Fincci Insight:
Many riders are surprised to learn that a 29-inch MTB tire and a 700c road tire actually share the same rim diameter (622mm). The difference lies in the width and volume. If you are looking for reliability and a perfect fit, checking the ETRTO 622 marking on our tires ensures they will seat perfectly on your wheels every time.

Explore the Full Fincci Tire Collection Here

Frequently Asked Questions (FAQ)

What is the ETRTO number and why does it matter?

The ETRTO number is the only truly standardized measurement for bike tires. It tells you the exact width and the internal diameter in millimeters. Using this number prevents you from buying a tire that is the right "inch" size but the wrong rim diameter.

Can I put a 29-inch tire on a 700c rim?

Technically, yes, because both share a 622mm bead seat diameter. However, you must ensure your rim is wide enough to support a high-volume mountain bike tire and that your bike frame has enough clearance for the extra width.

How do I find the correct tire size for my bike?

Look at the sidewall of your current tire. You will usually see a combination of systems (e.g., 700x35c and 37-622). When purchasing a replacement, matching the ETRTO (the numbers with the hyphen) is the safest way to guarantee compatibility.

Conclusion

Navigating bicycle tire markings doesn't have to be a guessing game. By understanding the relationship between the French, Inch, and ETRTO systems, you can shop with confidence. Whether you need 26x4.0 fat bike tires for snow or 700c tires for a triathlon, always prioritize the ETRTO standard for a perfect fit. Ready to upgrade? Check out the Fincci catalog for high-performance tires tailored to your specific riding style.