So you need to buy new tubes for your bike, but you have no idea what size to choose. What do you need to know to make sure you put the right size tube in your cart before you click the “Buy” button?
As a golden rule, the tube must match the diameter and the width of the tire. Whereas the diameters must match exactly, there is some wiggle room in the widths.
Tire dimensions can be confusing, but they don’t have to be.
With a little knowledge and the right information about your wheels, you can choose tubes and tires for your bike with confidence.
Which is exactly what you will be able to do by the time you’re done reading this post. In a moment, we’ll talk about how to read bike tire markings and how to match the size of an inner tube to your tire so you don’t have to go the bike shop twice.
How to Read Bike Tire Sizes
All bicycle tires have the diameter and the width written on the sidewall, usually as
Diameter x Width.
Although variations with
Width x Diameter are not uncommon, it’s easy to tell one from the other if you remember that a tire’s diameter is always greater than its width, without exception.
Most bike tires will also have a value for the maximum recommended tire pressure by the manufacturer (in Pounds per Square Inch, or “PSI”).
Multiple tire sizing systems are actively used in the cycling world. By far the two most prevalent, however, are the English-American and the European tire sizing systems.
Mountain Bikes (Inches)
The size of mountain bike tires is given in inches since manufacturers typically use the imperial, English-American tire sizing system.
For example, a 27.5 x 2.2 mountain bike tire has a diameter of 27.5 inches and a width of 2.2 inches.
Road Bikes (Millimeters… Sort Of)
The size of road bike tires is given in millimeters because manufacturers traditionally use the metric, European tire sizing system.
For example, the standard tire size for a road bike is a diameter of 622 mm and a width of 23 mm. With that said, this size can be represented in two ways:
- With the exact diameter and the width in millimeters. Namely, 622 x 23.
- With the diameter represented by three digits and the width in millimeters, followed by the lowercase letter “c.” For example, 700 x 23 c.
This means that a 700 x 23 c tire is the same as a 622 x 23 tire. It’s just that the tire’s diameter is represented in two different ways.
The seven hundred in 700c doesn’t stand for the diameter of the rim or the tire. Instead, it stands for the outer diameter of the full tires that once used to go on a 622 mm rim.
Contrary to what some cyclists think, the letter “c” on the sidewalls of road bike tires doesn’t stand for “clincher.” Instead, it was part of a French tire sizing system that’s no longer in use.
Related: What Does 700c Stand For on Road Bike Tires?
So in the world of road bikes, there are a lot of remnants of tire sizes—and tire sizing systems—that are no longer used. Just remember that a 700 x 23 c tire is the same as a 622 x 23 tire, and you’ll be fine.
Exactly what it says on the tires in your local bike shop depends on where you live and which manufacturer you buy your tires from.
How to Determine What Size Inner Tube You Need
Like tires, inner tubes have a diameter that’s measured either in inches (for mountain bikes) or millimeters (for road bikes). Unlike tires, they don’t have a single width value, but there are a range of widths to fit different tires.
Now that you know how to read tire sizes—and how to distinguish English-American from European tire sizes—it will be easy for you to choose tubes for your bike.
To choose the right tube for the your bicycle’s tire, make sure that (1) the diameter of the tube is exactly the same as the tire and (2) the width of the tire is within the width range on the tube.
For example, a tube for a road bike that’s marked as 700c x 20-25 mm will fit a 700c / 622 mm tire whose width is anywhere in the range from 20 mm to 25 mm. This would be common for a road bike, gravel bike, and many hybrid/commuter bikes.
Let’s say that your tire is 700 x 23c. This means 700 mm in wheel diameter and 23mm in tire width. You would then choose a tube that corresponds to that size: 700 x 20-25mm. A range of widths is given, since the tubes stretch slightly and can fit on other tires.
Or, if it’s a mountain bike, your tire might say 27.5 x 2.6. You will use the diameter of the tire (27.5 inches) and then choose the correct range of width, such as: 2.4-2.8 inches. (Fat-tire bicycles would require tubes over 3 inches in width.)
Can You Use a Smaller or Bigger Tube on My Tire?
What if the width range of your tube doesn’t match the tire width exactly?
Tube sizes vary depending on the tube manufacturer, so it’s common to have a little wiggle room. If a tube is a little too big, it can still be inflated in the tire, but it will contract and fold. This is a recipe for a pinch flat and/or a loud blowout.
An inner tube that’s slightly smaller than the rim/tire will usually expand to fit. However, a tube that’s stretched too thin can burst and puncture quickly, leaving you with a flat tire.
Neither option is particularly safe because you can’t know if you will get a flat tire while riding. As every cyclist who’s been through this or that will tell you, tires and tubes are not something you want to skimp (or compromise) on.
Does the Type of Valve Matter When Choosing Bike Tubes?
You, you figured out what size of tube you need for your bike’s tires. Before you load them in the cart and click the “Buy” button, make sure you’re looking at the correct valves.
Valves come out of the inner tubes and stick through holes in the wheels. However, be advised that your wheels were designed to work with one type of valve only, and you will have to buy tubes with the correct type.
Bike tubes have either Schrader valves or Presta valves.
Schrader valves are the same as the valves on car and motorcycle tires—short, stubby, and uniform, without a narrow screw tip.
Presta valves, on the other hand, are longer and skinnier and have a thinner screw tip at the top. These are most often found on road bikes with narrow tires.
Since Schrader and Presta valves have different widths, the holes in your tires will only fit one type of valve.
Does It Matter What the Inner Tubes Are Made Of?
Bike tubes are made out of either butyl or latex, both of which are rubber.
The everyman’s tube is made out of butyl. It’s cheap, puncture resistant, and capable of lasting for thousands of miles.
The pro cyclist’s tube is made out of latex. It’s pricey, light weigh, and rolls with minimal resistance. It’s also thin, difficult to mount, and loses air pressure much more quickly than butyl.
Unless you’re a pro cyclist, in which case you probably wouldn’t be reading this article, you’ll want to opt for a butyl tube.
Reading bike tire sizes and selecting tubes are among the skills that every cyclist sooner or later has to learn. Tire sizes and tire sizing systems can be confusing, and I hope this guide helped ease your learning curve and answer your questions.