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How do tyre pressure sensors work?

9th January 2023

What is a tyre pressure monitoring system?

A tyre pressure monitoring system, also known as TPMS, is installed into your vehicle to monitor the air pressure in your tyres. It will alert you when your tyre pressure that is under the legal requirement.  

Some manufacturers set the warning light to appear when the sensors detect a smaller decrease than the legal requirements to give drivers additional peace of mind. TPMS can determine whether your tyre is frequently leaking air due to a slow puncture or through the trim. This allows drivers to solve the problem before a flat tyre or accident occurs due to a blowout.  

Types of tyre pressure indicators

There are two types of tyre pressure indicators that work in different ways to identify if you have a problem with your tyre pressure: 

  • Direct TPMS 
  • Indirect TPMS 

How do tyre pressure sensors work? 

Direct TPMS 

These are the most common type of sensor as they are typically the most reliable. This is because it uses pressure sensors that are located within the tyre to track the exact pressure within the tyre – allowing for accuracy.  

A warning light will appear on your dashboard if your tyre pressure drops below a pre-set level. Once you have received the warning light, you should manually check your tyres and inflate the required tyre. Some direct TPMS may not specify which tyre is low, so you will not have to manually check them all yourself.  

Indirect TPMS 

This type of sensor incorporates the anti-lock braking system (ABS) as they don’t have their own sensor. The ABS sensor is located inside the wheel and works by tracking the tyres as they revolve. When a tyre is underinflated, the radius will be smaller than a tyre that is properly inflated, causing more irregular turns. When a wheel spins faster than expected, the sensor detects that the pressure could be low and alerts the driver accordingly. Though this system is less accurate than a direct TPMS, it is still able to tell you when a tyre requires more air.  

Where are tyre pressure sensors located? 

Generally, direct TPMS sensors are located within the tyre. Between the space between the tyre and the wheel trim. Indirect TPMS however, use the sensor on the ABS (anti-lock braking system). The ABS sensor is located near the brake rotor and may require your wheel to be removed in order to access it.  

Learn more about tyre pressure here or book in for a free tyre check at your local Merityre branch. Need more information? Contact our expert team who will be happy to help.