How to measure bicycle wheel size? (Step-By-Step)

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Cycling is a fun hobby that is growing in popularity these days. You can ride for pleasure, for exercise and even take part in events and competitions.

Due to the different kind of cycling activities, bicycles come with different wheel to cater to everyone. Bicycle wheels come in different sizes.

The standard sizes are 20, 24 and 26 inches but there are many more options available with different width sizes in each wheel. In this article, I will show you how to measure the size of your bicycle wheel.

Also Read: 10 Best Bicycle For Seniors

Systems of Measuring Bicycle Wheel Sizes

There are two systems to measure the size of bicycle wheels.

  • The standard method measures the diameter and width in inches.
  • The International Organization for Standardization (ISO) measures the width of the wheel and the inner diameter in millimeters.

Components you need to measure for determining the size of wheel

When determining the size of the bicycle tire, you need to measure two components. In the standard system, you calculate the width and diameter of the tire. In the ISO system, you measure the width and the inner diameter, also called the bead seat diameter.

In this article, I will go over both the systems and show you how to measure the wheel size in each system. It is important to know both sizes, as replacing wheels may turn out to be an issue if you know the size in one system, but they are available in the other system.

Measuring the wheels size in the Standard System.

It is important to note that the standard of measurement used in this system is inches.

You need to calculate the diameter and the width of the wheel in the appropriate unit. Furthermore, in this system the diameter of the wheel is indicated first followed by the width. The steps to measure the bicycle wheel size are given below:

  • Step 1: Make sure the bicycle is standing upright or is propped up against a wall. If you find that it is not stable, you may ask someone to hold the bicycle for you while you take the appropriate measurements.
  • Step 2: Take a tape measure and put it against the center of the bicycle wheel. Extend it along the wheel to the outer edge of the wheel in a straight line. Ensure that you end at the outer edge of the wheel and not the inner wheel.
  • Step 3: Take the reading in inches. This will give you the radius of the wheel. Since, you need the diameter of the wheel, you can multiply this reading by 2 to get the size of the diameter. A diameter is double of the radius.
  • Step 4: Next, you need to measure the width of the bicycle wheel. To do this, you need to measure the flat side of the bicycle wheel. Measure from one side of the wheel treads to the other. Note that this reading should also be taken in inches as the diameter.

Measuring the wheels size in the ISO system

Standard of measurement used in the ISO system is millimeter. Hence, all the measurements will be taken in this unit. Under this system, you measure the width of the wheel and the diameter.

The diameter in this case is to the inner rim of the wheel as opposed to the outer rim. This is how it differs from the standard system. Furthermore, according to the specifications of this system, you need to write the width first, followed by the diameter.

This is another area in which this system differs from the former. The steps to measure the bicycle wheel size are as follows:

  • Step 1: Prop the bicycle against a wall or ask someone to hold it to ensure that it is upright.
  • Step 2: Measure the distance from the center of the bicycle wheel to the inner rim of the wheel. Please note that you need to take this measurement in millimeters.
  • Step 3: This will give you the radius of the wheel. Just like before we can multiply the radius by 2 to get the diameter.
  • Step 4: If your tape measure does not show reading in millimeters, you can multiply the inches by 25.4. Multiplying inches by 25.4 gives the correct amount in millimeters.
  • Step 5: Once you have calculated the diameter, you can calculate the width of the bicycle wheel. Using the same process as indicated earlier, measure the width from one side of the tread of the wheel to the other. Again, this should be taken in millimeter. If you have measured it in inches, you can convert the reading to millimeters.

The above two methods are useful to measure the size of your bicycle wheel.

It is better to know both options, as there are times when the size is specified in the ISO system and others when it is indicated in the Standard system.

Standard System vs ISO system

Even though, both the systems are used interchangeably, it is important to note that the ISO sizing gives a more accurate reading when measuring at home. However, both systems are popular.

The size of the bicycle wheel size is usually indicated on the sidewall of the tire. It is usually indicated in both sizes. However, if the size in any system is not shown or if the readings have been rubbed off due to wear and tear, it is possible to calculate the size using the methods indicated above.

Measuring Circumference of the Bicycle Wheel

There are many instances in which it is helpful to know the circumference of the wheel. It is needed to calibrate the speedometer, odometer or GPS of the bicycle. If the circumference of the wheel changes, the speedometer can give inaccurate data.

Ways to measure the circumference

  1. You can calculate the circumference by applying the formula.

C = Pi x d

Pi is equal to 3.14, so you can get the circumference by multiplying the diameter by 3.14. Note that you use the diameter from the outer rim of the wheel and not the inner rim.

  1. Another method of measuring the circumference is to take a string and wrapping it around the outer rim of the wheel. You then measure the length of the string to get the circumference.

Conclusion

Once you have learnt the basics of measuring the size of your bicycle wheel, it will be useful for you when you want to order wheel replacements online. You do not need to call a professional for help to measure the size of your bicycle wheel. You can just do it yourself.

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