Picture this: you pull your bike out of the garage after months of neglect, only to find that the tires are completely flat.
It’s a frustrating situation that many bike owners have experienced. But why does it happen?
Do bike tires deflate over time for real, or is there something else at play?
Yes, bike tires DO deflate over time due to permeation and a couple of other reasons.
In this blog post, we’ll dive into the science behind why bike tires deflate over time and give you some tips on how to prevent it.
Why Do My Bicycle Tires Go Flat Over Time?
There are 3 reasons why bike tires deflate over time. Let’s go through each of these:
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The Nature Of Rubber
The main reason why bike tires lose air over time is due to their porous nature. Bike tires are made of rubber, which is a permeable material.
Rubber contains microscopic pores or gaps that allow air molecules to slowly escape through the tire walls.
This process is known as permeation or diffusion
Over time (even though it may not be noticeable at first) these tiny air molecules find their way through the rubber, leading to a gradual loss of air pressure within the tire.
Thinner tires tend to lose air more rapidly than thicker ones, but all tires will lose air over time.
This happens even faster if the bike is kept sitting on its wheels for extended periods as it puts additional pressure on the inner tubes.
This pressure can cause air molecules to escape from the tires at a slightly faster rate.
Temperature fluctuations can have an impact on the air pressure inside bike tires.
When the temperature drops, such as during colder seasons or overnight, the air molecules within the tire contract.
This contraction leads to a decrease in the volume of air, which in turn results in a decrease in tire pressure.
Cold temperatures can also make rubber more brittle and less flexible. When rubber becomes brittle, it loses some of its elasticity, making it more prone to developing cracks and fissures.
These cracks can weaken the integrity of the rubber and create pathways for air molecules to escape, leading to leaks and deflation of the tires.
If your bike is stored in a damp environment, this can cause the rubber to degrade over time.
We call this dry rot.
Dampness or high humidity in the storage area allows moisture to seep into the rubber and cause it to deteriorate more rapidly.
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It can weaken the chemical bonds within the rubber material and contribute to the breakdown of its structure.
How Quickly Do Unused Bike Tires Deflate?
In general, if a bike tire is left unused and properly inflated, it can typically maintain its air pressure for several weeks to a few months.
But this depends on factors like how and where it’s stored, the quality and age of tires etc..
So it’s generally recommended to periodically check the tire pressure and inflate them to the recommended levels, even if the bike will not be in use.
How To Stop Bike Tires Losing Air Over Time?
Unfortunately, it is NOT possible to completely prevent bike tires from deflating over time. We can’t change the nature of rubber.
However, what we can do is reduce the speed at which the tires lose air.
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Here are some recommendations:
Store in a Proper Environment
The best way to store bike tires is in a cool, dry, and dark place.
Avoid storing them in extreme temperatures, excessive humidity, or direct sunlight, as these factors can accelerate rubber degradation and increase the rate of air loss.
Use Tire Covers
Consider using tire covers to protect the tires during storage. Tire covers shield the tires from dust, moisture, dirt, and UV exposure, which can degrade the rubber.
This extra layer of protection helps maintain tire integrity and reduces air loss.
Rotate The Tires
Periodically rotate the tires while in storage.
Lift the bike and spin the wheels to change their position.
Rotating the tires helps distribute the weight and minimizes the development of flat spots, which can contribute to air loss.
In conclusion, it is completely normal for bike tires to lose air over time due to the porous nature of rubber. This gradual air loss occurs as air molecules permeate through the tire walls.
Thinner tires, with their larger surface area-to-volume ratio, tend to experience faster air loss compared to thicker ones.
However, all types of bike tires, regardless of thickness, will eventually lose air.