Does Inner Tube Width Matter? (Yes, Here’s How To Pick The Right Size)

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Ben Jones

Bike Maintenance, Other

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Does inner tube width even make a difference? Yup, it certainly does. Choose the wrong size and you might end up with tires that are too soft and squishy or inner tubes that explode. Let’s see WHY it matters and how to pick the size tube that’s the perfect fit for your bike.

Inner Tube Width Matters. A Lot. Here’s Why

The job of an inner tube is to push the sides of a bike tire outwards. Because the tubes are filled with air, this gives a firm, but somewhat cushioned, surface for you and the bike to ride along on.

When you’re riding, you want the tire walls to be pushed outwards by just the right amount.

Not enough and you’ll have problems. Too much and you’ll also have problems. More on these problems in a moment.

Think about inner tubes as essentially party balloons that are shaped like a doughnut.

Imagine that you cut through the doughnut and you’d see the circular cross-section of the inner tube.

The diameter of this circular cross-section (i.e. the width of the inner tube) depends on the amount of air that you inflate the tube with. As you can see in the diagram below, the width of the tube increases from fully deflated through the Minimum Recommended Inflation up to the Maximum Recommended Inflation.

inner tube width depends on level of inflation

Keep in mind that, just like party balloons, the more you inflate an inner tube the more the rubber walls will stretch out thinner.

Ok, so let’s take a look and see what the problems are with choosing a too big or too small tube.

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What happens if you use a tube that’s too small?

inner tube too small

If you choose a tube that is too small for your tire, it can lead to a couple issues.

If you blow the tube up to its Maximum Recommended Inflation, but no more, then you will have a gap between the outer edge of the tube and the inner edge of the tire. This will cause the tire to feel slack and can lead to damage on the tire walls, including cracks, as the rubber folds and bulges as you cycle along. Tires can be expensive, so this is not a good outcome.

You might be tempted to try and fill that gap between the tube and tire by inflating the tube beyond its Maximum Recommended pressure. Beware! If you do this you’ll find that the rubber of the inner tube becomes thinner and thinner. This makes it more susceptible to punctures from sharp objects and if you carried on inflating the tube, it would eventually pop.

TL;DR: A tube that is too small is more likely to pop or lead to tire damage.

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What happens if you use a tube that’s too big?

inner tube too big

Tubes that are too big can lead to other problems.

If your tube is too big for your tire then you won’t be able to inflate it to the Minimum Recommended pressure because it will be constrained by the tire walls.

This means that the tires will feel soft and squishy, particularly so when you’re riding on the bike.

This can cause punctures to your inner tube known as ‘pinch flats’.

Pinch flats happen when you hit a rock/bump/kerb with underinflated tubes. The tube wall is folded up and ‘pinched’ against the metal wheel rim and the rim punctures the tube. They’re also known as ‘snake bites’ because they often appear as two slash marks next to each other on the tube, as if caused by a snake’s fangs.

If your tubes are particularly underinflated it can also lead to damage to your wheel rims when your tires flatten against obstacles, rather than rolling over them.

TL;DR: A tube that is too big can lead to ‘pinch flat’ punctures and wheel rim damage.

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How to work out what the correct tube size is for your bike

choosing the correct tube size

We can see that inner tube width definitely DOES matter.

So, how do you pick the right size for your bike?

Luckily, this is easy.

If you squat down next to one of your bike wheels, you’ll see that there are lots of numbers and words/letters printed or embossed on the surface.

Follow these around the tire until you find a series of numbers that looks similar to the diagram above. You’re looking for something like “700 x 38c” or “27.5 x 2.25”.

These numbers are your tire size.

The inner tube you need will have the same first number (“700” or “27.5” in the example above) and a range that includes the second number (“35-43” or “2.1-2.4”).

Putting these pieces of information together, you should pick an inner tube that states it is size:

“700 x 35-43c” or
“27.5 x 2.1-2.4”
(though, obviously, you need to go by the numbers on your actual bike tires, not these examples!)

Now you’ve got your tube size, you can compare this against our Bike Inner Tube Size chart to buy the right one for your bike.

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