Why Do Bike Tires Go Flat In The Garage?

There are few things more disheartening than wanting to cycle on a bright and sunny day, only to discover a flat tire stands between you and freedom. I’ve had my fair share of mornings taken from me in this way, but thankfully I’ve since figured out why it happens. So, why do bike tires go flat in the garage?

Bike tires go flat in the garage because they are porous and constantly release air. When a bike is stationary on its wheels for long periods, it loses air quicker. Tires’ deflation rate can be slower by filling it with nitrogen because the air molecules are bigger and don’t escape easily.

Want to put unexpected flat-tire days behind you? There is some excellent information ahead, not only explaining why bike tires go flat but also what you can do about it! 

Why Do Bike Tires Go Flat In The Garage?

Bike tires get flat in a garage after sitting for a long time because the rubber is relatively porous at the molecular level and has millions of microscopic pores that continually release air. Although the rubber used to make a tube appears impenetrable to humans, it has pores large enough for air molecules to pass through.

Some air molecules escape via minute holes in the rubber, while others escape through the tire and rim gap. As a result, the tire’s air pressure will eventually equalize with the ambient pressure. The impact is also influenced by the size of the gas molecules employed.

When a bicycle (or anything else with rubberized tires, like a vehicle) is stationary in one spot, gravity and the bike’s weight compile to create strain. For this reason, it is ill-advised to store a bike on its wheels because it will lose pressure much faster due to flat-spotting. It is also an indicator to use your bicycle more often to balance the stress.

The deflation rate is also affected by the type of gas used to fill the tire. Many bikers, for example, use compressed CO2 chargers on the road to fill their tires if they have a flat tire; they’re compact, light, and simple to use. However, because CO2 molecules are smaller, they will leak out your tire faster than conventional air.

It might be a gradual leak from a puncture, valve stem, rim seal, or sidewall abrasion if your tire goes flat over a few days. Tires feature two types of rubber: the outer, which provides grip and structure, and the inner, which holds air. The internal rubber will break down if the sidewall is damaged (hitting curbs or driving flat).

How Do You Keep Your Bike Tires From Deflating?

In truth, you cannot prevent a tire from deflating altogether because it continuously leaks air. However, you can take some pre-planned measures to ensure it stays inflated for more extended periods.

Fill Your Tires With Nitrogen Instead Of CO2

The molecules of air are smaller than those of rubber. As a result, they move through the rubber. Just for that reason, if you leave a perfect tire for long enough, it will get flat.

Because nitrogen molecules are larger than oxygen and other gases, the pressure loss from filling the bike tires with nitrogen should be less substantial. But, of course, ordinary air contains around 70% nitrogen. Another advantage of nitrogen is that it does not degrade rubber as quickly as oxygen.

However, no one can fill a tire with pure nitrogen without vacuuming all the CO2. As a result, the problem will not disappear, but it will diminish to the point where it is nearly undetectable.

It’s prudent never to store a bicycle on its wheels. Bicycle tubes comprise mainly of buttle rubber and are prone to air leaks. Therefore,  bicycle tubes must be filled at least once a week and even more regularly depending on how much air the tubes have lost. Additionally, flat tires harm both the inner tube and the tire.

Ensure The Air Valve is Closed Correctly

It can happen that the tire valve was not closed correctly when last you filled your tire with air (it happens to the best of us). In this case, a tire can quickly lose all its air in one week. It is especially true with CO2-filled tires; they generally lose much pressure overnight. They are not entirely flat after that but need a refill again.

Other Reasons Why Bike Tires Deflate In A Garage

If you’re sure something specific is causing your bike tires to deflate, and you’ve been pulling out your hair, rest assured that your hairless days are nearly at an end. Here is a quick checklist for why your tire may be deflating in the garage.


  • A spoke end pierces the tube and protrudes through the rim strip. ​
  • The tube gets pierced by a sharp item already within the tire casing.
  • To avoid recurring flats, it’s usually a good idea to examine the tire casing when patching a flat.

Improper installation

The tube may be trapped between the rim and the tire bead, forming a bubble that bursts under the force of the bead’s compression.

Manufacturing defect

Occasionally, a brand new tube will have a material weakness that will cause a little rip.

Rim Damage

The tire bead cannot seat properly due to a flaw in the rim, causing a bubble to develop in the tube. The stress of riding with a bubble trying to come out between the rim and the bead will penetrate the tube if the flaw itself doesn’t.


When riding over a bump or pothole, an under-inflated tire compresses, trapping the tube against the rim and subjecting it to forces that generate two holes in a “snake bite” pattern.

Old age

Tires and tubes deteriorate with time, weakening the materials and reducing their flexibility. A slight weakness will evolve into a small rip that slowly seeps air if a catastrophic breakdown occurs first. Each time you pump the tire back up to pressure, this little rip will usually develop into a bigger one. 


  • Unfortunately, some individuals purposefully deflate the tires of abandoned bicycles.
  • Even worse, some people slash or puncture the tires of unattended bicycles on purpose.


Even though a Ziploc bag appears to be entirely non-porous, canines may detect illicit substances through these bags due to a bit of porosity. Bike tires work on the same principle, which is why they deflate when kept in a garage.

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