How To Measure Bike Wheel Size For Computer

By: Alex Bristol

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Are you looking to get a new bike computer but aren’t sure about your tire size or tire width?

Well, this is something we’ve all faced so don’t panic. in this article, we’re going to discuss some methods of measuring your wheel and tire size so you can get the right bike computer for you.

When you’re done with your tape measure you’re probably going to be looking for a good bicycle computer to become a part of your kit. In which case, you should definitely check out our guide on the best budget bike computer.

So, now you know what’s in store ahead, grab your bike tire, and we’ll show you how to properly measure it.

How Are Bike Sizes Measured?

Bicycle frame sizes and tire sizes differ, but neither of these applies when talking about whether a bicycle is 18 inches, 20 inches, 24 inches, 26 inches, or 700 millimeters. These metrics can seem confusing when you first look at a new bike.

Bicycle size refers to the tire’s rim diameter. Bicycles sizes are usually given in inches while some of the newer street bikes will be referred to as 700 millimeters.

An important thing to bear in mind is that 24-inch bicycles, for example, won’t always be the same size and the actual size will vary depending on the manufacturer.

The 700-millimeter street and racing bikes are of similar size to the older, now discontinued 27-inch rim bicycles, but the two tire sizes are not interchangeable. If you have 27-inch bicycles will most likely have to visit a specialty shop to find tires for their bicycles.

How To Measure Your Tire Size

You can find calculators online that will tell you your wheel size by simply filling in the details, however, if you’d prefer to double-check yourself then there are a few methods of measuring tire size.

Roll Out Method

One way to set your wheel size is to measure the distance you travel in one revolution of the tire with it inflated to the pressure you normally would use.

Use a wall

  1. Place your bike with the tire against a wall.
  2. Roll your bike forward until your valve stem is at the bottom of the wheel.
  3. Have you or someone else mark that spot with some tape or a marker.
  4. Then roll forward one revolution of the wheel so the valve stem is at the bottom of the wheel again.
  5. Then mark this spot with some tape or a marker.
  6. Finally, measure the distance between the two marks in mm and you have your size.

 Use paint or water

  1. Firstly, put a dab of wet paint on the pavement.
  2. Ride over it with your bike and keep riding.
  3. Each time your tire hits the pavement again, it should leave a mark of paint.
  4. You should then be able to measure the distance between marks.
  5. Measure that distance in mm and you’ll have your tire size.
Standard Method
  1. First, stand the bike upright by leaning it against a wall or using the kickstand. When the bicycle is upright, measure the bike wheel. If you are measuring the bike alone, a retractable metal tape measure will be sturdier than a plastic tape measure while leaving you a free hand.
  2. Measure the distance in inches from the ground beneath the tire to the center point of the wheel. This measurement is the wheel’s radius. Multiply the length by two in order to calculate the tire’s diameter. It should be around 26-29 inches in diameter as this is the average for bikes.
  3. After that, measure the flat part of the tire across the tread from one side to the other. The distance you measure is the tire’s width. As a rule of thumb, the wider the tread, the rougher the intended terrain, while narrower treads promise a smoother, faster ride.
  4. Put the diameter first and the width second then remember when purchasing a new tire that traditional, or standard sizes place the diameter first, followed by the width.
ISO Method
  1. First of all, check if your bike’s wheels are measured by the ISO system (International Organization for Standardization). This measuring system uses millimeters to signify the size of your bicycle’s wheel. If you don’t have a measuring tape with metric measurements, note that there are 25.4 millimeters in one inch and then determine the width with a calculator, multiplying inches x 25.4.
  2. Next up, you should ensure the bike is propped up against the wall. Measure in millimeters from the center of the wheel to only the inner edge of the tire. Then, once again, double the figure to determine the diameter. Most adult bicycle tires measured with the ISO system range from 650 to 700 millimeters in diameter.
  3. Measure the tire’s width in millimeters across the tread from one side to the other. Tires of various widths can be used on the same bicycle wheel, as long as the difference is not too much
  4. Lastly, list the width first and the diameter second. Remember when purchasing a new tire measured by the ISO system, the width is listed first, followed by the diameter.

Frequently Asked Questions

Why are power meters so expensive?

Because they are niche items that function as high precision, high-frequency torque meters that must also serve as bike components under adverse conditions power meters can set you back a few bucks. but they’re worth it if you take your cycling seriously.

What does a bike computer do?

Bike computers attach to your handlebars or stem and display a range of real-time information on your speed, distance, time, and much more. They have increased in popularity due to the increased usage of performance software, such as Strava, providing a world of statistics and data for cyclists everywhere. You can find out more about cycle computers by reading our article on what is a bike computer?

Do bike tire sizes have to be exact?

While your diameter measurement needs to be exact, your width measurement does not. This is because inner tubes stretch and they typically come in a range of widths.

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