Why Do Bike Tires go flat when not in Use?

Having a flat tire is something that is so common among bikers even with the best mountain bikes in the market. It happens once in a while. Whether it is pinch flats or a rare phenomenon of tube explosion, cyclists should always be prepared for any eventualities.  Most experienced bikers will also admit that flat tires are often a cause of inconveniences, and sometimes worry. Think about it this way. You’ve just registered for a triathlon for the first time then the unexpected happens, your tire bursts in the middle of the race.  How do you go about it?

Why Do Bike Tires go flat when not in Use?

When not in use, tires get deflated over time. This is mainly due to the permeability of the tube and the small size of air molecules. Slowly air molecules find there way through the tube and valve seal. When it is hot the air pressure will be higher and the process goes somewhat quicker. If you have a tubeless tire it can lose air due to the sealant leaking.

Well, the catch here is that like every unfortunate eventuality, flat tires can be annoying and very frustrating. The good news, however, is that with good bike care and maintenance, it is something you can control so that it does not happen often. In this blog, we answer a few questions about flat tires.

Why Bike Tires go flat if not in use.

Forget about buying a new pair of tires for your old mountain bike and think about an uninterrupted cycling experience. With it, you should, nonetheless, think about perfect tires whose tread will remain in good shape even after a long ride on rough terrain. Nevertheless, bikes do differ. As soon as you acquire a new one, you will want to make sure it is in good shape and condition. This way; basic tire care comes to mind. Will we look at this shortly, but first, here is a quick run through some of the reasons why bike tires go flat when not in use:

● Air Molecules vs. tube permeability

When not in use, tires get deflated over time. Like balloons that lose air day by day, air molecules in bike tires squeeze their way out through valve seal. Air, you must already know, can squeeze through anything even that which is seal-proof, albeit, it takes place slowly.

● Heated air vs. cold air

Most bikers will also admit that bikes lose pressure much slower when in use. The reason is simple. Like an excited biker, tires heat up when in use causing the air inside to expand. Keeping bikes for a long time without use means the air inside will contract, lowering the pressure, hence they flatten. Many scientific derivatives help explain this phenomenon of low tire pressure, but we will reserve that topic for another day.

Tubeless tires losing air

Tubeless MTB tires are getting more and more popular. They give you a smoother ride and help to maintain traction in rough terrain. But one of the disadvantages of tubeless tires is that they can lose air over time due to the sealant leaking.

Use the following steps to stop tubeless tires losing air:

  • New sealant: Add a new sealant every 2 to 3 months. Heat makes the sealant evaporate faster than normal, and the sealant is also absorbed by the material of the tire material and when it seals punctures.
  • Dirt buildup: Check for dirt around the spoke nipples. If you see excessive dirt around the spoke nipples it can be a sign of sealant leaking. The tire liner can be punctured and need to be replaced.
  • Wear and tear: Check for wear and tear of the tire. When you see threads in the sidewall you have to replace it.

Note: As the tubeless tire can start loose air during your ride you should make sure you always carry a tube and pump with you.

Why do bike tires go flat in cold weather?

As winter approaches, most bikers/cyclists are getting worried sick about low tire pressure. Talk of waking up early morning to a flat tire or stopping midway to fix a faulty tube. Cold weather does not auger well with tire pressure, to say the least.  So, the big question is this: Why does it happen?

Well, let’s explore some reasons to help explain this phenomenon. First, you should note that it is important to keep checking your tire pressure with a gauge during cold weather. If your bike does not have an inbuilt pressure gauge, then stopping by a refill station wouldn’t hurt. It will save you from unfortunate eventualities such as pinch flats that occur when riding on low-pressure tires.

Now, on explaining why flat tires are a common phenomenon during cold weather, think about air density.  During winter, the air becomes denser or heavier, whichever way you like to call it.  As a result, tires lose their pressure. Most of the time, it has nothing to do with a puncture or tiny air spaces in the tube.

A common understanding among experienced cyclists is that during cold weather, pressure in bike tires drop by at least 1 psi with every 10 degrees Fahrenheit temperature drop. Thus, it is often a real challenge monitoring tire pressure in real-time, especially for cyclists whose bikes do not have a monitoring system. Take for instance, waking to ride on a chilly morning, you should be sure to check psi and top it up if necessary before setting out.  But after riding for a while, the tires warm up causing the air inside to expand. Do not run the risk of waiting for a week before adding pressure.

Do bike tires go flat if not used?

A straightforward answer is, yes, bike tires lose their pressure if not used. Unless you have a pressure gauge to test the difference, you may not notice such a change for a long time. When you go out riding your mountain bike, air molecules inside tire tubes get excited, something that causes them to expand and fill up empty spaces on the upper parts. Leaving your bike idle for weeks or months results in contraction of air molecules and soon enough, they either settle on the bottom of the tube or escape through pressure valve.

Moreover, when not in use, bike tires harden because they do not heat up. The latter only happens when you go out cycling. Depending on whether you are riding on wide or narrow tires, the rate at which tires lose pressure varies. Take note that when in use, you should often check pressure using a gauge and fill up when necessary. This is, however, not the case when you leave your bike unused for a long time. In the latter case, the only possibility is a flat tire or low pressure.

How can you cushion your bike against unprecedented flat tires?

Thus far, every cyclist out there must be asking one big question. How then do you cushion your bike tires against flattening during cold weather or when not in use? First, you have to admit that riding on low-pressure tires will cause more damage than good to your bike. From pinch flats to wreaking havoc on the rims, you must be careful not to end up with a grounded bike.

With the above situations at the back of your mind, it is true that proper bike maintenance goes a long way in helping to keep your treasured possession in good shape and stead. Thus far, a few points worth noting about using your bike include but are not limited to the following:

● Ride on ideal bike tire pressure

There are different types of tires and each has a unique pressure rating. They include:

  • Tires of mountain bikes that should have a pressure of between 30 and 50 psi. Anything below this range means your tire is likely to experience pinch flats on rough terrain.
  • Psi in the range of 60 and 80 is the ideal gauge value for casual and urban bikes.
  • For bikers/cyclists who use road tires, you must always check to make sure psi is not less than 100 or more than 140.

Taking the above psi ranges into consideration, it goes that any value that is below or above could be a trigger for flat tires or uncomfortable riding experience. For instance, when you under inflate bike tires, pinch flats are the most likely outcome as soon as you start riding. While overinflating tires may not be something to worry much about, it could lead to tire burst in some cases.

● Keep checking pressure

As a bike owner, you have one holistic responsibility. Keep checking psi value on your tires. It may not be often but it is crucial that you do, at least once every week, if not after every cycling expedition. For those who own high-end mountain, urban or road bikes that have pressure gauges, checking pressure is something you should do very often.  However, owners of low-end bikes must ensure to carry pressure gauges at all times or stop by pressure stations very often.

● Check tires for foreign objects

While this may sound like a basic tire maintenance routine, many bikers/cyclists ignore it. Thus, we include it here as a reminder that after a long day on the road, tires may have run over broken glass, sharp rocks or any other objects. If left unchecked, these foreign bodies will pierce through tubes causing unprecedented punctures in the middle of high-octane riding experience. These are often not a cause for immediate worry because new tires with good tread will withstand them. However, they would potentially ruin your cycling experience one fateful day as they dig deeper and deeper into the treads.

● Check for wear and tear

No matter how much money you spend on new tires, wear and tear is a common phenomenon with machines. It is, therefore, imperative that you keep checking your bike tire sidewalls for cracks, dryness, and other damages. This is because wear and tear of tread increase the rate at which tires go flat without warming on the pressure gauge.


In summary, bike tires will go flat as it is common. However, with good care and maintenance, it is possible to control how often it happens. We hope this blog has helped shed some light on why bike tires go flat and how to guard against it.

Recent Posts