How to measure bike wheel size? (3 Methods That Work)

Wondering how do you measure your bike wheel size? If you are buying a bike, the owner or dealer will let you know the size of your wheel.

However, if you want to be sure or don’t have that info, we will show you how to find it. Here’s how to measure bike wheel size.

How to Measure the Wheel Size

Check Tire Markings

Most tires have markings on the sidewalls showing their rotating direction, size, and the amount of air you should pump into them.

Check the rear or front tire, and you’ll see some numbers printed on them. For mountain tires, you’ll see something like 29 x 2.5. This means the tire is 29 inches just like the wheel and also 2.5-inch wide on the rolling surface.

You see, the tires are always classified by the size of wheel they’ll fit or their bead size. Therefore, tires make it easy to interpret the size of your wheel.

However, if you can’t see the markings on your tires, perhaps because the tire didn’t come with them, or they got erased, then you’ll have to follow the next options to get an accurate measurement.

Check your Bike Manual

If you shop bikes new, your manual has all the bike details you need to know about your bike. If not, you can contact the bike shop, and they’ll provide you with the details. If you bought it used, you could ask the first owner.

Alternatively, check your bike’s details, such as the make year and name, and model. You will also get the serial number of the bike under the frame, which, if you search online, will give you details of your bike. You can also contact your bike manufacturer and ask them the size of your bike wheels.

Measuring the Bike Wheel Size: The Longer Process

The methodology of finding the size of your wheels is more involving but painless. You’ll be required to do the measurements yourself because you would like to confirm the actual size or have no answer to your question.

There are three measurements you need to pay attention to, namely:

  • Tire diameter
  • Tire width
  • Circumference

Grab a measuring tape, follow the steps below, and write them on paper.

Step 1: Lean the bike against the wall

Leaning your bike on the wall or upright position makes it easier to take measurements. Suppose you have a bike stand, the better, especially for your mountain bike. MTBs have wide tires that are more likely to tip and complicate the whole process.

If you don’t have a stand, and you can get assistance from a loved one or a friend, ask them to hold the bike for you. They’ll help make things easier for you as the process is short. If it doesn’t work, you can easily remove a wheel by rotating the quick release screws or thru-axles anticlockwise and pulling the wheel from the bike.

Step 2: Measure the tire’s diameter

The bike has settled, and you want to measure the rim diameter. Place the tape just at the center of the wheel and extend it to the edge of the tire. You will get the tire’s radius and double the length to get the actual diameter of the wheel.

The tire size varies with the bike type. For example, road bikes use the ISO methodology, which requires you to measure in millimeters instead of inches.

MTB wheels are sized according to inches. Therefore use a tape measure with either of these units to make your work easier.

Step 3: measure the width of the tire

The width of the tires refers to the surface area that makes contact with the ground. Put the tape on top of the tire from right to left, or vice versa, and make sure it’s going across the tread. For the MTB, you’ll be using the traditional method to determine the width of the wider tires – inches.

For a road bike, you’ll be using the ISO method to measure the narrow tires. Here is what you’ll be measuring.

  • The wider width of the mountain bike tire
  • The narrow width of the road bike tire.

Step 4: Combine the different measurements

Presuming you already have the diameter and the width of your wheel, you should combine them. However, the traditional sizing and ISO system will have different results. It’s simple! If you are using inches, place diameter first and then the width next, and if you are using the ISO, do the opposite. Place width first.

We assume the tire you were measuring belongs to the bike. Record that information somewhere to refer to it when you are about to buy new tires. If the calculations don’t seem accurate, you can ask for assistance from your bike mechanic.

Step 5: Calculating the circumference of the bike wheel

Now you have combined the diameter and the width, and you have something like 26 x1.25 inches. The next step is calculating the circumference of your bike’s wheel. It’s crucial to do so if you are using the manual bike computer. If you are using Garmin or any other GPS computer, you can skip this process.

If you skipped that math class, or in case you forgot, you need to multiple the diameter with pie, which is equal to 3.14.

For instance, if the wheel radius of your bike is 29 inches, multiply that by two to get the diameter. In this case, the diameter is 58 inches. If you multiply it by 3.14, the answer will be 182.12 inches. That’s the circumference of the wheel.

Another way to find the circumference of your bike Wheel

A string would work a miracle, that’s if you opt for the long process. Just wrap the string along the center of the middle and side threads. The method will give you a rough figure of the wheel’s width. Whatever results you get, carry them to the nearest inch.

Understanding all MTB Wheel Sizes

MTBs come with different purposes and so different wheel sizes to fulfill those purposes. Most trail, cross country mountain bikes, and some Enduro and downhill bikes come with 29” wheels. Dirt jump bikes usually have 26” wheels. Most DH bikes have 27.5” wheels.

Choosing a bike according to wheel size should trickle down to your style of riding and what you are comfortable with. Most people prefer 29-inch wheels. That’s the widest wheel for production bikes, but some brands have developed oversized wheels that haven’t hit the market officially.

Here are the common MTB wheel sizes.

26” Wheels

The first mountain bikes in the 80s came with 26” wheels largest. They were the standard wheels for American cruiser bikes. 26” wheels were a common thing for decades, and many mountain bike lovers of the past two decades started with these.

26” wheels are still common, especially with kids’ bikes and folding bikes. The advantage of running 26-inch wheels is that you can find spares easily anywhere around the world.

They are still off-road favorites even though most riders have shifted to 27.5” and 29” wheels. Back then, you could also get a 16-inch bike and 20-inch bike, but they’ve become rare.

Advantages

  • The spare parts are available and easy to find anywhere
  • They are easier to use in rough terrain with many sharp corners than larger wheels.
  • Their weight, stiffness, and strength can be adjusted.

5” Wheels /650b

27.5” wheels are equivalent to 650b wheels. The wheels were first used on touring bikes in France as early as the 1960s. These wheels were slightly smaller than what’s been used on road bikes today – 700c wheels.

The wheels are still in use today, but the same wheels are sized as 27.5-inch wheels when it comes to mountain bikes. The mountain bike adopted this wheel size a few years before moving to 29” wheels. Both wheels remain popular options.

The 27.5” wheels roll over obstacles more easily than 26” wheels, roll downhill faster, but harder to push uphill than the 26” wheels. 27.5” wheels were also said to offer better contact patch and traction. Surprisingly, most DH racers prefer these wheels. However, these wheels are not easy to find at the spare shops.

Advantages

  • Fast accelerators
  • Stiffer and stronger than 26” wheels.

29” Wheels

29” wheels are the largest production wheels you’ll ever find and are for the larger bikes. They have become so mainstream that, unlike the 27.5” wheels, they are available everywhere in the world.

The 29-inch wheel is the same size as the road bike’s 700c wheel. The only difference is the tire width. Mountain bike tires are generally wider and dwarf the road bike wheels, but don’t be confused. The wheels are the same size.

Like the adoption of the 650b by the MTB world, the 700c became the 29” inch, and bikes with these wheels are known as 29ers.

The wheels came with more advantages than disadvantages. They offer better rolling over obstacles, are faster, but maneuverability was compromised.

Bike brands have improved the geometry to make these large rollers more flexible and to handle trails better. The only difference between the road bike and MTB rims is that the latter are wider to accommodate the huge MTB tires. You’ll see these wheels in almost every trail bike lineup.

Advantages

  • Offer better control on rough terrain, smoother, and stable.
  • Run over obstacles better.

Maintainance of Your Bike Wheels

Inspect the Rims and The Hubs

A rim will last over 20,000 miles if using rim brakes and forever if running disc wheels. If you are running rim brakes, you should check your wheels more often. Wet and muddy conditions will make your bike wheels wear faster.

Most rims have a visible line that runs along the braking surface on the rim or a single hole that disappears with time to indicate that your rim has worn out. If the sidewalls are too thin, the bow will split under the pressure of the tire pressure.

Also, inspect the hubs and make sure that the bearings are regreased and all worn-out parts. If your hub is in sound condition, you can replace the rim without replacing the whole wheel.

Tighten Your Spokes a Bit After Some Time

Apart from hitting a rock, another reason why your wheels are not true might be loose spokes. Squeeze two spokes towards each other with your fingers. You’ll be able to tell that the spokes are tight or loose.

To tighten them, use your fingers to feel which section of the wheel tends to pass closer to the frame. Grab a spoke wrench and tighten the spokes slightly and evenly. You’ll notice the wheel is true after tightening a few spokes, but if it doesn’t work, you’ll need to take the next step.

True the Wheels

The work-stand is the last final solution to your truing problems. Always ensure that your wheels are true all the time, and when they are not, try to fix the issue. Depending on your bike brake type, you’ll notice things are not working the same. 

If you don’t fix it, your wheel will start wobbling, and if you are on rim brakes, you’ll get a brake rub. In the end, your wheel will be weaker and worn out. You might need to replace the wheel sooner than you were supposed to if you want a perfect bike.

Final Remarks

Measuring the size of your wheel is a straightforward process that won’t take much of your time.

However, if you can’t identify your bike’s wheel size and need an extra hand, contact us, and we’ll assist. Don’t make the common mistakes of assuming the size of your wheels or getting the wrong tires.

From riding to school since the age of 13, attending BMX races and events with his dad to himself conquering 10+ trails across the globe, for Rob, his Giant Stance 29 2 2020 is the friend that makes everything better. He is also a proud member of the International Mountain Bicycling Association (IMBA).

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