How to Identify causes of air loss & how to deal with it

The consequences of driving on under-inflated tyres can be serious. The worst possible outcome would be a blowout while driving at high speed. More certain, however, are damage to the tyres, higher fuel consumption and impaired steering.

When a tyre is under-inflated it changes shape. Contact with the ground is transferred from a central location toward the edges. Eventually, you are almost driving on your sidewalls, while the middle points, where tread is optimised to grip the road, actually begin to lift away from it.
 
Friction with the road now resists both forward movement and steering, increasing your expenditure on fuel, while shear forces in the increasingly flexible tyre begin to weaken its internal structure.
 

Tyres Lose Pressure for Five Reasons

Air loss can never be completely avoided because of osmosis. Most materials are porous to some degree, and rubber certainly is. In other words, air slowly escapes directly through the tyre itself - no puncture is required. The rate of osmosis depends upon the construction of the tyre (especially its inner liner) but can be as high as 3 psi per month.
 
If your normal tyre pressure is around 32 psi, you can see how quickly a problem can develop. Most tyres leak slower than that, but many are dangerously flat after just months of neglect.
 
Slow punctures are the leading cause of more rapid deflation. If you’re losing 1-3 psi per day, this is almost certainly the cause, but puncture losses can be slower and therefore take longer to spot. Nails, screws, shards of glass, metal or sharp rocks get embedded somewhere in the tyre grooves, where they are almost impossible to spot. Even if you find them, removing them is likely to increase the rate of deflation - not cure it.
 
The third most likely cause of air loss is a faulty valve. A common cause is damage from over-tightening the valve cores. If you have your tyres checked at a specialist garage like Protyre, you’ll have the peace of mind of knowing your valve cores have been set properly using a purpose-designed torque wrench.
 
Impacts are a fourth cause of air loss. Each slight run-in with the curb when parking or turning, or when hitting rocks and pot holes on bad roads, can deform the tyre sufficiently to accelerate air loss from each of the previous three causes. Of course, if your tyres are already in poor condition, an explosive deflation can happen there and then.
 
The fifth reason for low pressure readings isn’t even a tyre fault. It’s the weather. Both temperature and air pressure vary day by day and affect the pressure readings you get from the tyres. In the UK you can usually ignore this fluctuation (it’s about 1 psi for every 10 degrees Fahrenheit or 5 ½ degrees Centigrade), but being aware of it will help you interpret the changes you see when checking your tyre pressures.

Regular Checks and Maintenance

Most manufacturers recommend tyre pressure checks every fortnight or before any long journey. Your manual will tell you the correct values for your particular vehicle. If in any doubt, call in at a Protyre garage for advice and an expert inspection.

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About the author

David Sholicar

David is the National Retail Operations Manager for Protyre. One of David’s areas of responsibility and ...

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