How Does A Tire Pressure Monitor System Work?

Tire pressure systems were first seen in luxury vehicles in Europe back in the 1980’s with the first manufacturer to adopt it being Porsche on their 959 models from 1987-89.

Tire pressure monitoring systems became compulsory for all passenger cars and light trucks sold in the U.S from September 2007. This is known as the TREAD act which came into play to assist drivers in being aware of their tire pressure. So how do these tire pressure monitoring systems (TPMS) work?

Direct TPMS uses sensors inside the tires that send information to the vehicle’s computer. If the pressure is 25% lower than the optimal pressure, the TPMS light will glow on your dashboard. Indirect TPMS does the same by using the ABS system to detect a tire that is rotating faster than the rest.

These two systems work in very different ways but both get the same job done adequately. The direct TPMS is the more reliable and accurate system between the two. Let’s have a look to see why.

Direct TPMS

Direct TPMS is the more expensive type of system because it uses actual gauges inside each tire to accurately measure the pressure at any time. These sensors communicate with the computer of your vehicle wirelessly and give it the tire pressure readings.

These sensors are able to check the tire pressure at any time without needing the car to rotate its wheels first. So it can check your tire pressure as soon as you turn the ignition in the parked position.

Direct TPMS uses batteries that last around 7 to 10 years these days and are not replaceable. This means that you’ll have to replace the whole tire pressure sensor when the battery dies. Usually, you’ll be advised to replace all sensors if one or two have run their full battery life cycle because the other batteries will shortly follow.

A direct TPMS usually consists of a pressure sensor, microcontroller, oscillator, radion frequency transmitter, system controller, analog-digital converter and voltage regulator (battery management)

Indirect TPMS

Your antilock braking system (ABS) has a wheel speed sensor that can check to see if one or more tires are rotating faster than the others while driving. An underinflated tire will have to rotate faster than the others to keep up as its circumference is smaller and therefore has to rotate more times to cover the same distance as an inflated tire. So when the ABS picks up one or more wheels rotating faster than the rest it will trigger your TPMS light on your dashboard.

Needing the wheels to rotate for this system to work means that it won’t warn you of low tire pressures while parked. The benefit of this system is that you’ll never have to replace physical pressure gauges inside the wheels.

How Much Does It Cost To Replace A Tire Pressure Sensor?

At the time of writing this article the cost to replace one TPMS is between $40 and $100 depending on what you choose. The best thing to do is get a few different prices including labor and go for the best deal. The good news is the price is getting cheaper as technology evolves.

How Accurate Are Tire Pressure Monitor Systems?

Tire Pressure monitoring systems are accurate to the nearest PSI which is perfectly acceptable to serve its purpose. After all, the TPMS system is there to warn you if the pressure drops by 25% and not to warn you of minor pressure changes. You must still check your tire pressure at a service station periodically or get yourself a tire gauge to keep in the glovebox to maintain your tire pressure properly.

Where Are The Tire Pressure Sensors Located?

With direct TPMS, the tire pressure sensor is located in the rim of the wheel or in the tire pressure valve. Either way it’s concealed and closed up inside the tire.

With indirect TPMS there are no physical pressure sensors, your vehicle’s computer determines the tire pressure by checking the speed of the tires via the ABS wheel speed sensors.
How Can You Check Your Tire Pressure Sensors?

You can use a gauge to check the PSI of the tires and then check what the TPMS of your vehicle says to see if it’s giving accurate measurements. The main thing to check with TPMS is the warning light, the warning light will glow if the tire pressure has dropped by 25% of its recommended pressure.

You still need to perform regular visual tire checks and measured pressure checks with pressure gauges regularly yourself.

Recommended Tire Pressure Ranges

Normal passenger vehicles and small trucks have a tire pressure range of 30 to 35 PSI. For your specific PSI recommendation, check the sticker in the door jab of your car. (Sometimes under the hood or inside the fuel cap)

Over or underinflated tires will wear down inconsistently and will cause the to replace tires quicker than normal. It can also cause the tires to heat up and blowout.

Tire Pressure Safety Tips

It is absolutely crucial that you drive with tires that are inflated to the correct pressure. Besides wearing your tires down inconsistently, a tire that is not correctly inflated can blow out at any time leading to disaster.

Tire blowouts used to be the cause of many more accidents before the TREAD act came into play in 2007. Needless to say, tire pressure monitoring systems have saved many lives since it became compulsory in all vehicles.

Tire pressure monitoring systems are extremely useful but you should also always visually check your tires before getting into your car to drive. Walk around your car and perform an inspection of all four tires checking for any that look underinflated. If you’re unsure, you can check the tire pressures at the nearest service station.

A sticker with the optimal tire pressures for your vehicle is stuck on the inside of your door jab, under your hood or sometimes on the inside of your fuel hatch.

In terms of safety, your vehicle’s tires are the most important parts of the vehicle for you to inspect daily and maintain.

Even if you just purchased the best tires on the market, you could easily suffer from a puncher from a nail in the road. If you walk around your car and check the tires every time you drive it, you will save yourself from unnecessary drama.

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