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How to Measure the Size of a Bike Wheel

When it comes to maintaining or upgrading your bike, knowing the size of your bike wheel is crucial. Whether you need to replace a worn-out tire or want to upgrade your bike’s rims, having the correct measurements is essential. In this guide, we will walk you through the steps on how to measure the size of a bike wheel accurately.

Why is Wheel Size Important?

The size of your bike wheel affects various aspects of your ride, including speed, stability, and comfort. Different types of bikes have different wheel sizes, and each size is designed for specific purposes.

Before we dive into the measurement process, let’s understand the key components of a bike wheel:

  • Rim: The outer metal ring that holds the tire in place.
  • Spokes: The metal rods that connect the rim to the hub.
  • Hub: The center part of the wheel that attaches to the bike frame.
  • Tire: The rubber covering that provides traction and absorbs shock.

Measuring the Bike Rim Diameter

The most crucial measurement for determining the size of a bike wheel is the rim diameter. Follow these steps to measure it accurately:

  1. Remove the tire: Start by deflating the tire and carefully removing it from the rim. This will expose the rim and make it easier to measure.
  2. Locate the bead seat diameter: The bead seat diameter is the inner diameter of the rim where the tire beads sit. It is usually marked on the side of the rim. Look for a number followed by “ISO” (International Organization for Standardization) or “ETRTO” (European Tire and Rim Technical Organization).
  3. Measure the rim diameter: Using a tape measure or a caliper, measure the distance between the two opposite points of the rim’s inner edge. Make sure to measure from the bead seat, not the outer edges of the rim.

Once you have the rim diameter measurement, you can use it to determine the appropriate tire size for your bike.

Understanding Tire Sizing

Bike tire sizes are typically indicated by a series of numbers printed on the sidewall of the tire. The most common format is “A x B – C,” where:

  • A represents the tire width in millimeters.
  • B represents the tire height or aspect ratio as a percentage of the width.
  • C represents the rim diameter in inches.

For example, a tire labeled “700 x 25c” has a width of 25 millimeters and fits a rim with a diameter of 700 millimeters.

Checking the Tire Size Compatibility

When replacing a tire, it is essential to ensure compatibility with your bike’s rim. The rim diameter measurement you obtained earlier will help you find a suitable replacement. Additionally, you should also consider the tire width and clearance within your bike frame.

Consult your bike’s user manual or the manufacturer’s website to determine the recommended tire sizes for your specific bike model.


Knowing how to measure the size of a bike wheel is vital for maintaining and upgrading your bike. By accurately measuring the rim diameter, understanding tire sizing, and checking compatibility, you can confidently choose the right tires for your bike. Remember to consult the manufacturer’s guidelines for specific recommendations and always prioritize safety when making any changes to your bike’s wheels.

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