Navigating the world of bike wheel sizes can initially feel like deciphering a secret code. You’ll encounter terms like 26 inch, 650b, 700c, and 29er, and understanding what these measurements signify is key to everything from replacing a tire to choosing the right bike accessories. This guide will demystify bike wheel measurements and show you exactly how to determine your bike wheel size.
Decoding Bike Wheel Sizes: MTB vs. Road
Bike wheels are typically measured using two systems, depending on the style of bike.
For mountain bikes (MTB), wheel sizes are generally expressed in inches. Historically, 26-inch wheels were standard, but now 27.5-inch and 29-inch wheels have become increasingly popular, offering different advantages on trails.
Mountain bike wheel with tubeless sealant
Road bikes, on the other hand, commonly use the ISO (International Organization for Standardization) system, which measures in millimeters. The most prevalent road bike wheel size is 700c, although you might also find 650b or 650c sizes, particularly on smaller frames or gravel bikes.
Road bike wheel for inflation
Finding Your Bike Wheel Size: Initial Checks
Before you grab a measuring tape, there are a few places to quickly check for your wheel size.
- Rim Stickers: Some wheel manufacturers conveniently print the wheel size directly onto the rim stickers. Inspect your rims closely for any labeled sizes.
- Tire Sidewall: Your tire sidewall is another prime location to find size information. Look for markings like “700x25c” or “27.5×2.2”. These markings indicate the wheel diameter and tire width.
- Bike Frame (New Bikes): If your bike is brand new, the wheel size might be specified on a sticker or label somewhere on the frame itself.
If these quick checks don’t yield results, don’t worry! Measuring your bike wheel is a simple process.
Step-by-Step Guide: Measuring Your Bike Wheel
To accurately measure your bike wheel using the ISO system, you’ll need to measure from the center of the hub to the outside edge of the rim. This measurement represents the radius. Doubling this measurement gives you the diameter.
Measuring bike wheel diameter with ISO system
Once you have this measurement in millimeters (mm), you can use the size guide below to identify your wheel size in both ISO and inches (where applicable).
Bike Wheel Size Guide
| ISO Diameter (mm) | Inches (MTB Size) | Road Bike Size | Common Bike Types |
|---|---|---|---|
| 305 | 16 | Kids Bikes, Folding Bikes | |
| 406 | 20 | BMX Bikes, Kids Bikes | |
| 507 | 24 | Kids Bikes, Older Mountain Bikes | |
| 559 | 26 | 650c | Older Mountain Bikes, Some Road Bikes (smaller frames) |
| 584 | 27.5 | 650b | Mountain Bikes, Gravel Bikes |
| 622 | 29 | 700c | Mountain Bikes, Road Bikes, Hybrid Bikes |
Key Points to Remember About Bike Wheel Sizes
- 27.5 inch vs. 650b: These terms are interchangeable when discussing mountain bike wheels. Both refer to the same wheel diameter.
- 29 inch vs. 700c: While technically the same diameter (622mm), mountain bikers will always refer to them as 29 inch, and road cyclists as 700c. The difference often lies in tire width and intended use.
- 24 inch wheels: Commonly found on children’s bikes and dirt jump bikes.
- 20 inch wheels: Standard size for BMX bikes.
- Tire Width: Bike wheel sizes are often followed by another number indicating tire width, for example, ‘700 x 35c’ or ‘27.5 x 2.10’. The first number refers to the wheel diameter, and the second to the tire width.
Understanding how to measure your bike wheel and decipher size markings empowers you to maintain your bike, choose the correct components, and confidently navigate the world of cycling.
