Why do bicycle tires lose air?

We all have had it before. You’re going to ride your bike yet again after one week and you see that you have to fill your tire up. You’re left wondering why do my bicycle tires lose air?

There is a difference between the normal leakage and a slow leak which is important to note – as all bike tires will always slowly leak air out of the innertube.

When you are riding, and when the bike is in storage, some air will be released. This is because as the air inflates the innertube, the molecules in the tube will spread apart and release small amounts of air.

In a road bike, it is possible to lose 5-10 psi per day. In my own experience, I will lose about between 2-3 psi per day, with an average closer to 2. When I go on a long ride of 50 miles or more, typically I will come back with about 5-10 psi lower than when I left for that day.

It is useful to know this so that you aren’t surprised that you are filling up your bike tire with air more often than not. To save my hands, I typically will opt for an electric pump.

I have been using these for years, and the technology has not been perfected so after about 1 year the pump will become louder than it was when you bought it. Then afterwards, just like the reviews state, the motor tends to be less effective or simply stop working after about 2-3 years.

I still like it because for about $40, I don’t have to think about tire pressure at all – just blow up and go. Though, I am excited for when over time these bike tire inflators’ technology will become better for longer durability and quieter usability.

Why do bicycle tires lose air?

Bicycle tires lose air because the elastic inner tubes are not air tight. This might seem strainge for the very thing that is supposed to hold air to not be air tight, though this is because the innertubes are made of rubber.

In order for the material to be able to stretch, and deflate back to normal when you are filling the tube with air, this means that space in between the individual bits of mass needs to be created.

This is similar to the reason why a balloon will slowly deflate over time. The rubber that the balloon is made of will decrease in size as it slowly loses air out of the rubber that it is made of.

This is also why the air will seep out faster when there is higher pressure and the tube has a larger surface area surrounding it.

Why won’t my bike tire stay inflated?

A bike tire will typically lose 5-10 psi per day. My bike tire innertubes will typically lose 2-3 per day with exception to the days that I go for a long ride where it loses about twice the amount of air.

If the ride has a lot of hills, change in elevation, and bumps, then perhaps a touch more. The tires will not stay inflated because your innertubes will naturally slowly leak air from the innertube.

It is important to know that your bike tire should leak this amount, though if it is leaking any more air you may have a slow leak. Read here to learn how to fix a slow leak.

Changing your tire for the most part, you will not slow down the leaking in your tire.

Why is my bike tire losing air without a hole?

Your tire may have a slow leak that you are unaware of. Finding them is fairly simple, and patching them is easy as well.

If you are in a pinch or on the road, then it is smart to patch the tire. If you find that you have a slow leak at home, or near a shop, I would recommend replacing the tube over patching it. The amount to patch the tube versus replacing the entire tube is negligibly higher.

Why does my tire slowly deflate after a few days?

Your tire may slowly deflate after two days because it is old, or has a very small puncture somewhere in the tube.

When the bicycle inner tube gets older, small tears can form in the skin of the inner tube. This will cause air to leave the inner tube when you are riding and the tube is full.

If your bike has a small puncture, this can be caused from a small thorn, or a piece of glass from a car window (Thank you San Francisco) on the ground. When the item does not penetrate the innertube fully, the tire will slowly deflate over time rather than doing the standard “pop” that most are used to.

This will occur over a couple of days.

How do you fix a slow leak in a bike?

The way to fix a slow leak in a bike is to either patch the tube, or to replace the inner tube.

We typically recommend replacing the inner tube, because to replace an innertube is about $10-$20 at a shop. When you are patching a tube, the cost may be around $10, though if it is not done correct, then you may need to replace the tube, or redo the patch later on.

Conclusion: Why do bicycle tires lose air?

Your bicycle tires lose air more than likely for two reasons, The first is that you have a slow leak. This can be caused by your tire being punctured by glass or a thorn.

The other reason why your tire may lose air is if the inner tube is beginning to age. When the innertube begins to age, then the tube may start to leak air at a faster rate than typical.