Why tyres lose pressure

One of the questions that customers often ask our fitters is "why do tyres lose pressure?" There are a number of possible reasons. At first glance, a tyre may seem perfectly fine, yet it slowly loses pressure over time, requiring regular inflation.

In our experience in dealing with vehicles both old and new, we have identified the primary reasons as to why this may be the case. Also, and perhaps crucially, this knowledge helps us to determine whether or not you may need to replace your tyres, or if the pressure loss is normal.

Permeation is normal

First of all, it is important to understand that all tyres will lose pressure over time. The natural materials which make up the tyre means that permeation will occur, with air passing through the structure of the tyre. Permeation usually affects the pressure of a tyre by between 1-3 psi per month. This will vary depending on the make and model of the tyre, with different blends of rubber resulting in different rates of pressure loss. This makes it important to check the pressure of your tyres regularly to ensure they stay within manufacturer's tolerances.

Using nitrogen

In order to combat permeation, some drivers opt to fill their tyres with nitrogen rather than air. This is due to the fact that nitrogen molecules are larger than those of oxygen, thus reducing the permeation rates.

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Temperature changes

As temperature reduces, the air pressure within a tyre will also reduce. If you are in a region with dramatic fluctuation between winter and summer temperatures, it may be wise to reinflate your tyres during winter. Similarly, the differences in day and nighttime temperatures could cause tyres to have reduced pressure in the night. It is not recommended to reinflate here, as the pressure would increase beyond the recommended level as it becomes warmer in the daytime.

Damage to the wheel

Whilst permeation and temperature changes are no cause for alarm, damage to the wheel rim could soon see you heading to replace your tyres. Flat spots on a wheel or any deviation in its shape may compromise the seal between the wheel and tyre. This could easily result in your tyre losing air and becoming flat over a week or less. Wheels and tyres can be damaged at any point, for example when encountering potholes. Similarly, wheel corrosion can compromise the tyre seal.


Valve stems are likely to deteriorate over time due to wear and tear. If your tyre loses pressure by more than the maximum expected due to permeation, it is possible that there is a valve issue.

Tyre damage

If you drive over a nail, it is unlikely to cause your tyre to burst, but your tyre will steadily lose pressure. Punctures can usually be repaired if they occur in the tread. Damage to the sidewall will require a replacement.
If you would like any additional help or information, please don't hesitate to contact us. We stock leading tyre brands including Pirelli at competitive prices and we offer a range of free tyre and vehicle inspections.

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Protyre offer free tyre checks at all of our garages. Click the button below to book your vehicle in and let our technicians advise on the best tyres for you. 

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Tom Boote

Tom has over 5 years’ digital marketing experience within the automotive industry in both B2B and B2C ...

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