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There is no shortage of worried or hesitant cyclists online asking if they can use a smaller bike inner tube than they are supposed to. If you are one of these many hundreds of concerned cycling customers, then look no further!
In this article that question will be answered, using a focus on the exact mechanical reasons for using or not using a smaller inner tube.
So, can you use a smaller bike inner tube than you are supposed to? Yes, you can. Bike inner tubes are made of a pliable enough material that it should stretch to fill the gap of a wider tire. In some instances, cyclists even prefer the smaller inner tubes as they are less difficult to get into the tire.
If you happen to be caught short with only a smaller bike inner tube than your tire would normally use – you should be fine.
Of course, most sources would suggest that you match your inner tube size with the size of your bike’s tire.
This article will go into more detail on why that may be, why some prefer to use a smaller inner tube and explain a bit more about different types of inner tubes and why the inner tube size might not even be the most important factor when thinking about replacing your inner tube.
If that sounds right up your street, then read on, as we find out together: Can I use a smaller bike inner tube than I am supposed to?
So, will a smaller inner tube work in a larger tire?
The function of an inner tube is to provide the correct amount of air to fill the tire in a pressurized space, keeping the tire functional even when the force of a human being atop a metal frame is pushing it into the ground.
As air disperses to fill the volume of its container, a fixed and sealed container like a bike tube will inflate as much as it can to accommodate a certain amount of air. Like a balloon, if this is much too high then it can burst quite easily, and if this is too low it will not have any proper bounce or shape.
To continue the balloon analogy – the inner tube can inflate a lot. It can even inflate so much that it can effectively fill a tire of a completely different size as it was intended for!
In order to meet this increased size of tire, however, your smaller inner tube will need to inflate more than it usually would. The material these inner tubes are made from is pliable enough that it is not massively more likely to burst, but it is always worth remembering that you have inflated it past its optimal size.
When most people talk about size here, they are talking about thickness and width. Due to the butyl rubber of the inner tubes, this attribute does not matter a massive amount, and there is generally a small range that will fit most tires.
If you are thinking about inner tube size though, it is essential that you match the right inner tube diameter to your bike’s tires. If that requirement is not met, you will be much more prone to flat tires during your cycles – meaning you will be searching up this exact question again in no time.
What are the benefits to using a smaller bike inner tube?
So, while we have established that it is fine to use a smaller bike inner tube in your tires, are there any actual benefits to this approach?
Many cyclists would argue that there are some significant benefits.
Firstly, a less thick inner tube is going to have one obvious benefit: a lighter bicycle. If your tire suddenly has a reduced capacity for air storage in its tires, then you can cut the extra weight from those tires significantly.
Smaller tubes have been known to save up to around 20 grams in overall bicycle weight, perhaps making it ideal for longer haul trips or fast sprints. Those two types of cycles are where the weight differential will be felt the most.
Secondly, changing inner tubes can be a hassle. They are tricksy beasts, the inside of a tire, and leveraging a tire properly to fit a full size or larger tube in can be exceedingly difficult.
If you are ever caught in a position where you have to change over an inner tube by a roadside or on a trail, you are going to want to be able to make the switch fast. A normal inner tube will simply not allow that to happen, with all of the extra care you have to take to avoid the well trapping or pinching parts of the tube.
Negatives to using a smaller bike inner tube.
There are of course downsides to not using the technically correct bike inner tube.
Some claim an increased risk of punctures and flat tires are a likely consequence of using the wrong size of inner tube. While this is technically possible, it is unlikely. The likelihood of a puncture or flat is more determined by the tube’s diameter and the strength of its tires.
It is worth noting, however, that repairing a punctured inner tube to fit a larger tire is much more difficult. A plastered inner tube that is much smaller than its tire will be difficult to properly inflate to the right level of stretch to fill the larger tire.
Other information to know about inner tube types.
Why are some inner tube types different?
So far we have covered the benefits and disadvantages of a smaller inner tube used for a larger tire size.
I would contend that there is a much more important distinguishing factor that should impact your choice of inner tube much more: the valve.
While some sizes of inner tubes are largely interchangeable with each other, valve types are not. There are two common types of valve in inner tubes: the Presta or the Schrader.
Prestas are narrower, thinner valves that are often used on mountain and road bikes. You can find examples of them here:
Schraders are much thicker products, being the same type of valve that is used in car tires. They tend to be less common than Presta valves. Examples of this can be found here:
You physically cannot fit Schrader valves into wheels built for Prestas, and it is inadvisable to try fitting Presta valves into Schrader wheels as a long-term fix.
Can you use a larger inner tube?
You can, and some prefer the extra security it provides. However, they will be more likely to catch and nick on your wheel rims.
How long do inner tubes last?
Due to the chemical composition of butyl rubber, this depends entirely on how they are stored. Tubes stored properly in dry, cool conditions should last you for years, sometimes even decades.