What Does 700x38c On Your Bike Inner Tube and Tire mean?

When you buy new tires, inner tubes, and tubes from tire shops, do you notice anything special about the size of the tires? Do you see any numbers written anywhere on the tube or tire?

You might find numbers such as 700x38c. This means your tube is made for a specific bike with a certain number of inches in diameter (the number written).

A 700x38c tire is an approximate tire size of 27 1⁄2″ x 1 1⁄2″ (inches in diameter).

Sounds simple, right? Unfortunately, it isn’t as easy when discussing bike tire sizes.

Even if you replace your 700x38c inner tube tires with the exact same tire size, you might run into issues later on.

Why is that? There are several reasons why it happens.

But first, let’s understand in detail what 700x38c means exactly.

What Does 700x38c Inner Tube Mean?

The simple answer is that the 700x38c inner tube number is used to indicate the size of your bicycle wheel (its diameter in millimeters).

This is important because it tells us how wide your tires are relative to each other.


A larger number indicates a wider tire. In this case, we’re talking about the size of the tire itself, not the rim upon which it sits.

700 refers to the nominal diameter of the bead seat. This is the distance around the outside edge of the tire where the beads sit.

If you look at your bike’s frame from the front, you’ll see three holes that hold the frame together. Each hole corresponds to one of the three beads.

The bead closest to the center of the wheel is called the bead seat.

38 refers to the width of the tire, measured across the widest part of the tread.

C refers to the old French classification system for measuring the size of a bicycle wheel. The letter C stands for Compresseur (compressor), which refers to the rim’s shape.

There are five classes of rims based on the degree of compression of the spokes. Class C is the most common type of rim found on bicycles today.

What Tire Size Do I Need?

The question of what size tire you’ll need is one that many people ask themselves every day. Three main factors determine what size tire you’ll want:

• Your weight – If you weigh less than about 70kg, you’ll probably find that 700x25mm tires work well.

• Your intended use – A road bike might require something different from a mountain bike.

• How much grip you need – This depends on how fast you plan to go. You don’t necessarily need a lot of traction, but you do need some.

Bike Tire

To make sure you buy the correct size, follow these steps:

• Measure the circumference of your current tire.

• Multiply that number by 2.5cm to obtain the width of the rim.

• Divide the resulting figure by 25 to calculate the diameter of the new tire.

If you’re unsure whether you’ve got the right-sized tire, check out our handy guide here.

How Do I Change A Flat Bike Tire?

If you are replacing a flat tire, it might seem like a daunting task. However, there are several things you can do to make the job easier.

First off, you’ll want to find out what type of tire you’re dealing with.

Then, you’ll need to determine whether you need to use a special tool such as a tubeless rim tape system. Once you’ve figured out what tools you need, you can start working on changing your tire.

To change a tire, you’ll need a few items, including some basic tools, a spare inner tube, and a patch kit. You’ll also need to have a pump handy.

Here’s a step-by-step tutorial on changing a bicycle tire and inner tubes.

The Bike Tire Conversion isn’t Always Accurate

If you’re trying to figure out why someone would be interested in tires in inches, you first need to know how the sizes convert from millimeters to inches.

The metric and European tire standards (ETRTO) systems measure tires in millimeters.

Bike Tire

Alternatively, the imperial system uses inches.

If you’re switching from an ETRTO or Metric tire to an Imperial tire, you’ll need to convert tire sizes. This conversion doesn’t come out accurately every time.

There might be small differences between the two systems.

For example, if you take a 25 mm x 1.95 cm tire and convert it into an 18″ x 3.0″ tire, you will get a difference of 0.7″. In other words, the actual measurement of the tire will be 24.3″ instead of 23.8″.

This means that when converting from one system to another, you should always round up or down depending on where you are in the conversion process.

For instance, converting from a 25mm x 1.95cm to an 18″ x 3″, you would round up to 19″ x 4″.

This is because the conversion rate is inaccurate enough to account for the rounding error. Therefore, you must round up or down accordingly.


We hope this article has helped answer what 700x38c inner tube means and all other questions regarding the proper size of your bicycle tire.

We recommend using the above information to help you choose the best tire for your needs.

Thomas Kersten

Hi, I am a passionate biker, and I have been riding for more than ten years and share my biking tips and tricks with the world. I've tested more than 300 bikes.

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