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

By David Sholicar

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.

Identify causes of tyre air loss

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.

Get a professional's opinion on your tyres for peace-of-mind

Free Tyre Checks are available at any of our garages. Don't risk driving on illegal tyres, keep you and your passengers safe. Click the button below to book a free check at your local Protyre garage:

Free Tyre Check

Share with your friends...

About the author

Article Author Photo
By David Sholicar
David is the National Retail Operations Manager for Protyre. One of David’s areas of responsibility and expertise is dealing with the DVSA and MOT’s for Protyre. As the Authorised Examiner Designate Manager ( AEDM ) David deals with applications for changes to the many Vehicle Testing Stations ( VTS’s) including managing the growth of the Number of MOT testing stations that Protyre operate, allocating MOT tester roles, and monitoring the MOT Test logs to ensure that Protyre MOT standards are maintained as the best in the industry.
View authorArrow right
What you should know about Tyre Pressure Monitoring Systems
Most motorists know that they should keep track of the pressure in their tyres both for comfort and safety, with the added bonus that the right tyre pressure will help your tyres to wear more evenly and last longer. In addition, tyres at the right pressure consume less fuel and save you money.
Find out moreChevron
Tyre Puncture Repair: Can You Fix a Car Tyre Puncture?
There is never a convenient time to puncture a tyre, so whenever and wherever it happens, you will be keen to get the problem fixed as soon as possible.
Find out moreChevron
Help! What is the best tyre pressure for my car?
Under-inflated tyres negatively affect handling, safety and the overall performance of your car - make sure your tyre pressures are correct.
Find out moreChevron