Tyre Myths: You Won’t Lose Air If You Use Valve Caps

What Job do Valve Caps Really Do?

Cars are designed with precision and thought. Every detail, even down to the small things, are placed there for a reason – that includes your valve caps. However, there is a lot of misinformation around what value caps are for. Do they stop the air coming out of your tyres, or are they for something else?

What Are Valve Caps?

Valve caps are placed on the stem of your vehicle tyres. They are small, made of plastic or metal, and may seem insignificant. However, they play an important role in tyre maintenance.

A valve cap is designed to protect the Schrader valve, which a valve stem core is threaded through. The stem core is what keeps the air or nitrogen in your tyres.

Why Do You Need Valve Caps on Your Tyres?

If a valve cap is not fitted to your tyres, the stem is left unprotected. Dirt and moisture can enter the valve stem, causing blockages or damaging the valve.

Not having a valve cap does make your tyres more susceptible to losing air. However, having your valve cap in place does not mean that your tyres won’t deflate.

What Should Your Tyre Pressure Be?

Tyre pressure is measured in PSI (pounds per square inch) and varies for each vehicle. Typically, on newer cars, the recommended tyre pressure is listed on a sticker inside the driver’s door. For some vehicles that have all the new mod-cons, the current pressure of each tyre can be displayed on the dashboard. It will warn you when you are over or under the recommended tyre pressure.

Low tyre pressure can make your car less fuel-efficient and impact the safety of your vehicle. Maintaining proper inflation is important to keep your tyres wearing evenly and improves their longevity.

If your vehicle is doing coast-to-coast drives over the interstates, or regularly going on unpaved roads, you should check the pressure more frequently.

What Causes Your Tyres to Lose Air?

Every car owner or fleet manager should aim to maintain proper tyre pressure. Knowing what causes tyre deflation can help you put preventative measures in place, to keep your tyres at the correct air pressure.

·      Movement of Air (Osmosis)

Osmosis of air through the tyres can lead to the loss of 1 to 3 PSI every month. The material and manufacture of the tyre impact the osmosis. This is as much as 10% of your tyre’s air pressure.

·      Slow Punctures

One of the most common causes of loss of air pressure is a slow puncture. A nail or other debris stuck in the tyre can cause it to lose 1 to 3 PSI every day. Often you won’t notice the puncture until there is significant deflation of your tyres, so it’s good practice to check your pressure regularly.

·      Impact Breaks

Hitting the curb or driving over large rocks or other objects on the road can cause sudden and excessive air loss. Impacts such as these will be noticeable almost immediately and you will need to call a roadside response like NRMA or RAC to come and fix or replace the tyre.

What Do the Experts Have to Say?

Most tyre and vehicle manufacturers give the same advice for having valve caps on your tyres. Bridgestone’s advice is typical of that from tyre manufacturers:

Valve caps are designed to keep water and dust particles out. Air will inevitably escape through the tyre rubber in all directions even with the valve caps in place. It is recommended to regularly inflate your tyres to ensure that they are at the right pressure and perform as they should.

In short, tyres will lose air pressure over time with or without a valve in place. However, the valve does help to retain air and does an important job of protecting the valve stem from dirt and moisture. Checking your tyre pressure regularly and ensuring your valve caps are securely in place are two ways you can ensure good tyre maintenance.

Is your tyre losing air pressure? Feel free to contact us to book an appointment or ask any questions you may have.

Keeping your family and fleet safe on the road,

Dean Wood

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