One of the most common problems you will have as a cyclist is punctures.
No matter how great your tires are, there’s always a thorn or piece of flint that can get inside and cause issues. A replacement inner tube is typically the fix when these pesky punctures come around.
One of the biggest challenges when it comes to replacing the inner tube is finding the correct size. As someone who has spent years working as a bike mechanic, I am very used to hearing, “What size inner tube do I need for my bike?”
In this article, we’ll provide you with a bike inner tube size chart, along with some helpful information to get you on your way!
Let’s get into it!
Bike Inner Tube Size Chart
First things first – if you don’t already know how to find tire sizes, then this inner tube size chart will probably look like gibberish.
If that’s the case, check out all the information below first to find out how to work out your tire’s size, what all these numbers mean, and which type of valve you’re going to need.
What Size Inner Tube Do I Need?
This all comes down to the tire size and the valve type.
There are three bits of information you’ll need to find:
- Tire Diameter (e.g. 700c, 650b, 26″, etc.)
- Tire Width (typically measured in mm, but often written as “c”)
- Valve Type (almost always Presta or Schrader, as discussed above)
Find The Tire Size
The first method is to look for the size written on the tire’s sidewall. It will typically be written in the form of the bicycle tire’s diameter and width.
It might look something like this:
- 700c x 25c
This would be a pretty typical road bike wheel. The “700c” part refers to the tire’s diameter (700c is the same size as 29-inch MTB tires), and the “25c” refers to the tire’s width (25 mm).
If you can find this information on the tire, you can then use it with the inner tube size chart below to find your replacement inner tube.
Unfortunately, not all tires have their size written directly on the sidewall. If you can’t find this information, your next option is to find the tire code.
Use The Tire Code
The tire code comes in two numbers. The first is the tire width, and the second is the bead seat diameter (the wheel’s diameter at the point where the tire’s bead is seated in mm), also known as the “ISO” tire size. It will look something like this:
- 50-559
This would be a typical 26″ mountain bike tire. The “50” is the tire’s width (50 mm or 1.9″), and the “559” is the bead seat diameter, which is equivalent to a 26-inch tire.
- 28-622
This shows that the tire is 28 mm wide, and fits a 700c wheel.
Here’s a quick cheat sheet to know how ISO tire codes translate to the most common wheel sizes, as they’re written in either “French” style (e.g. 700c) or in inches (typical for mountain bikes).
Using the tire code is an excellent method, as very few bicycle tires out there don’t state the code. It’s also good to learn this for sizing bike wheels and getting the correct replacement tires.
In my opinion, when it comes to what inner tube size I need, this is the best way to go.
Measure The Tire Width Yourself
Finally, if you can’t find either the tire size or tire code stamped anywhere on the sidewall, you can measure the tire from the wheel and the tire itself.
Take a tape measure from the wheel’s center to the wheel rim’s outside edge and double it for the bead seat diameter.
Then, use a tape measure to measure the tire’s width from the top. This isn’t an exact science, as in practice tire widths vary slightly from manufacturer to manufacturer when inflated.
Get The Right Valve Type: Presta Vs Schrader
Before you start finding the right inner tube size, you first need to identify the type of valve your inner tube will need to be fitted with.
Inner tubes also come with different valve types, and it’s essential to choose the right one as otherwise it won’t fit your rim properly.
Presta Valves
Presta valves are longer and thinner (see the image above). They’ve long been standard on road bikes, but are now commonplace on mountain bikes too.
Note that some aerodynamic wheels with deep rims require longer valves or extension valves, so be sure to check.
Schrader Valves
Schrader valves are shorter and wider. They’re the same valve type you get on your car tires.
They’re becoming less common for modern bikes, but are still found on some mountain bikes, hybrids, and city bikes.
There are other varieties such as Dunlop valves, but almost all the inner tubes you’re likely to come across will be either Presta or Schrader valves.
Why Is It Important To Have The Correct Size Inner Tube?
When I first started, I underestimated the importance of the correct inner tube size and, unfortunately, learned the hard way.
Here’s why it has to be right:
Tire Shape
The inner tube shapes the tire at the correct pressure. If it is the wrong size, you can shape the tire wrong, and it won’t work as intended. An inner tube too large stretches it too much outward, possibly off the bead, and an inner tube too small won’t fill it enough.
Safety
The wrong-size inner tube isn’t going to work as well as you might want. It is too small, and it becomes overstretched, and you risk a blowout. Too big, and you risk pinch flats. Both these result in the tire losing pressure quickly, which can be unsafe.
Durability
Another big factor is durability. If you have the right inner tube, it sits inside the tire as it should. This means there’s reduced internal friction, and the inner tube has the correct thickness at full capacity. This heavily improves durability and can reduce punctures.
Efficiency
Tires with the right inner tubes are actually more efficient. It reduces rolling resistance, keeps the inner tube width correct, and makes installation much easier compared to using the wrong-size inner tube.
Will The Wrong Inner Tube Size Fit My Bike?
We’re often asked, “What inner tube size do I need? And does it matter if it’s not perfect?” Interestingly enough, if you are in an emergency and can’t find the correct size tube, then the wrong size can fit.
It has to be fairly close, and it might be challenging to fit, but if this is no other option, you can put a similar-sized tube in.
I don’t recommend it, but while backpacking in countries with limited bike shop stock, it is something I have had to do before. Eventually, when I got the correct inner tube, I did swap it out, but as a last resort, it got me out of a muddle.