Your Questions Answered: Tire pressure and TPMS sensors

Answering the internet's most popular questions about tires and their monitors

Seasons change, and shifting temperatures are in the forecast. Even when it doesn't feel like much, the expansion of hot air or shrinkage of cold air often impacts tire pressures, which is why you’re more likely to see a warning from your Tire Pressure Monitoring System (TPMS) as seasons swing.

Many new cars use a Tire Pressure Monitoring System (TPMS) to electronically monitor tire pressure in real time. The TPMS sensors can give drivers an important warning the moment they get a flat tire, and can alert of a potential loss of tire pressure for other reasons, too. If there's a problem with the inflation pressure of one or more tires on your car or truck, TPMS gives you an early warning to take corrective action.

Checking and maintaining the inflation pressure of your tires is vital for maximum safety, efficiency, and performance in your vehicle. Maintaining the proper pressure also ensures that your tires will last as long as intended, saving you money in the long run. Thankfully, checking and adjusting your tire pressure is one of the easiest parts of maintaining your car.

Whether or not your car is equipped with TPMS, regular manual tire pressure checks are very important. Still, a survey commissioned by the Tire and Rubber Association of Canada (TRAC) says that Canadian drivers have been making some pretty serious mistakes around checking and adjusting tire pressure on their cars and trucks.

Firstly, nearly a third of surveyed drivers hadn't checked their tire pressure in the past year, and fewer than one quarter reported checking tire pressures monthly, as is recommended by the owner's manual. For a closer look at the most common mistakes when it comes to tire inflation, check out this story.

Remember: to avoid tire pressure problems, check your tire pressure manually and regularly using a quality pressure gauge, especially during shoulder seasons.

Below, we’ve compiled some of the internet's most popular search questions on tire pressure, TPMS systems and tire pressure sensors, and asked some experts to chime in with their best answers.

"Yes, All TPMS sensors are powered by a small, built-in battery. These batteries, which are similar to what you might find in a vehicle key fob, have an average life expectancy of about five years. Unlike the battery in your key fob, these batteries are non-replaceable and the sensor will need to be replaced when the battery reaches the end of its life."

Tim Orpen, Manager, Mechanical Program at Kal Tire

"The most common failure of TPMS sensors is due to the sensors’ built in battery failing at the end of its life cycle."

Tim Orpen, Manager, Mechanical Program — Kal Tire

"There are two different systems: Indirect TPMS and Direct TPMS

Indirect TPMS works with your car's Antilock Braking System sensors. If a tire's pressure is low, the tire will rotate at a different speed than the other tires. When the rotation seems wrong, the information is detected, and signals are sent to the car's computer to trigger the dashboard indicator light. An indirect TPMS doesn't measure the tire air pressure like a Direct TPMS would.

Direct TPMS uses a sensor installed in each wheel to measure air pressure in each tire — not just wheel rotation data from the anti-lock brake system. Direct TPMS sends all data to a centralized control module where it's interpreted, and if tire pressure is lower, it will trigger your dashboard indicator light."

Nico van Wieringen, Operations Manager — OK Tire, Parksville, B.C.

Direct tire pressure monitoring is a more premium technology and is more commonly used on tires with lower sidewall profiles and larger sizes, where speed difference alone is no longer an effective indicator of low pressure. See owner's manuals for details on what capabilities each vehicles’ system has."

Toyota Canada

"With an Indirect TPMS, the information is taken from your car's Antilock Braking System's (ABS) wheel speed sensors. Direct TPMS transmits all data wirelessly via low-frequency radio to the vehicle's onboard computer. Each sensor has a unique serial number to identify itself from other vehicles."

Nico van Wieringen, Operations Manager — OK Tire, Parksville, B.C.

"An under-inflated tire will ride a bloated contact patch (the part of the tire that contacts the road) that exceeds the tire manufacture's design specifications. In addition to increased wear on the tire and reduced performance, the enlarged contact patch on an under-inflated tire will bring increased rolling resistance. Put another way, it’ll take more energy (i.e. fuel) to move the tire and car down the road."

Jonathan Scott, Technical Expert, Toyo Tires

"Yes, they would be covered under normal warranty terms. However, if a vehicle is brought in for a warranty concern and is found to have non-OEM sensors installed, an issue caused by those sensors would not be a warrantable repair."

Toyota Canada

"Unlike our U.S. counterparts, vehicles sold in Canada are not required to have factory-installed TPMS systems."

Tim Orpen, Manager, Mechanical Program — Kal Tire

"Most TPMS sensors are fairly accurate, however it is still important to manually check your tire pressures monthly. Don't just rely on the system itself."

Tim Orpen, Manager, Mechanical Program — Kal Tire

"A sensor is constructed like a valve stem, made of similar rubber or with a rubber gasket. As the rubber heats up, cools, and ages, the rubber can crack and leak. Another reason for air leaking is corrosion, usually caused by moisture between the base of the sensor and the wheel. Any dirt, grit, or brine trapped in this spot can eventually cause a slow leak."

Jonathan Scott, Technical Expert, Toyo Tires

"Although not as common as passenger-vehicle TPMS, some RV and utility trailers now equip tire pressure monitoring systems as well. Depending on your vehicle manufacturer's software accommodations, the trailer TPMS systems may be able to connect to your vehicle and actively display the trailer tires’ air pressures through the vehicle information system."

Tim Orpen, Manager, Mechanical Program — Kal Tire

"No — different sensors are made to work with different TPMS systems. The frequencies and communication algorithms differ between different brands and generations of TPMS systems. For example, some older systems use a different number of characters in their identifying codes than newer systems, meaning that the sensors cannot be interchanged as the systems will not recognize their unique identifying code structures."

Toyota Canada

"The cost of TPMS sensors varies, but is usually between $30 and $200 per sensor. Calibration of the sensors also differs greatly, with some calibrating automatically and others needing a calibration at a cost of $100 or more. On average, the majority of sensors can be replaced for between $50-60 each."

Tim Orpen, Manager, Mechanical Program — Kal Tire

"Although not as common as passenger-vehicle TPMS, some RV and utility trailers now equip tire pressure monitoring systems as well. Depending on your vehicle manufacturer's software accommodations, the trailer TPMS may be able to connect to your vehicle and actively display the trailer tires’ air pressures through the vehicle information system."

Tim Orpen, Manager, Mechanical Program — Kal Tire

"Yes, and most vehicles manufactures recommend that the TPMS be calibrated after a tire rotation or seasonal tire change. The process is usually done through the vehicle's infotainment system and may require driving up to 50 km while the TPMS "detects" variations in tire pressures. It's important to note that tires should always be inflated when they’re ‘cold,’ ie. with at least at least three hours’ cooldown since they were driven. The pressure level should match the vehicle manufacturer's recommendations noted on the tire info placard or in the owner's manual."

Jonathan Scott, Technical Expert, Toyo Tires

"When the temperature drops, air contracts and as the air molecules get closer together. This reduction in air volume causes tires to lose their pressure. These smaller air molecules can also naturally work their way through the pores of a tire's rubber, causing further pressure loss. Additionally, rubber hardens in colder temperatures, sometimes causing additional air loss from the seal of the tire where it meets the rim. Most tire repairs in winter months are due to seal leaks."

Tim Orpen, Manager, Mechanical Program — Kal Tire

"If your old TPMS sensors are still working when you get new tires, they can be reused. In Canada's harsh climate, TPMS sensors may rust into a wheel and require replacement."

Nico van Wieringen, Operations Manager — OK Tire, Parksville, B.C.

"We recommend doing a monthly inspection of your tires that includes checking the air pressure with a reliable tire pressure gauge and comparing the result to your to your TPMS indication. If there's a significant difference between the tire pressure gauge and TPMS setting, you may want to have your tire dealer inspect the TPMS monitors for any issues."

Jonathan Scott, Technical Expert, Toyo Tires

"TPMS sensors do not freeze, but they may indicate low tire pressure in colder weather even though the tire is properly inflated. A general rule of thumb in the tire industry that the air in the tire will condense (the air molecules will move closer together) at approximately one PSI for every 10ºC drop in temperature. This phenomenon may be short-lived, as the tire pressure will expand to the correct level as the vehicle is driven and the air in the tire warms up."

Jonathan Scott, Technical Expert, Toyo Tires

"If a fault is identified with the tire pressure monitoring system, a TPMS light will illuminate or flash, and a message may be displayed. Faults can arise from any number of issues including electronic interference from external devices, improperly programmed sensors, or a fault with a sensor or part of the vehicle system. It is important to note that the vast majority of TPMS issues arise from aftermarket or non-genuine parts being used. If a fault occurs, the first step is always to ensure you have OEM sensors, though this may not be possible to determine without disassembling the tire from the rim."

Toyota Canada

"Winter tires, as well as all-season or summer tires, should always be set to the manufacturer's recommendations for the vehicle. This specification is usually found on a large sticker in the driver's door jamb, owner's manual, or sometimes inside your fuel door. Remember that tires should be checked ‘cold’ and not immediately after driving, as this will alter the pressure reading due to increased tire temperature from road friction."

Tim Orpen, Manager, Mechanical Program — Kal Tire

"Vehicles equipped with run-flat tires are required to have a tire pressure monitoring device on the vehicle, but relying on TPMS to monitor your tire pressures is not recommended. Run-flat tires should have their air pressure checked monthly as it is difficult to visually distinguish if the tire pressure is low."

Tim Orpen, Manager, Mechanical Program — Kal Tire

"Like all gases, the air in a tire will expand as it heats while driving. Vehicle manufacturers have taken this into consideration when recommending the "cold" or baseline psi settings on the tire information placard. This is important to ensure the tire's proper performance."

Jonathan Scott, Technical Expert, Toyo Tires

"The principles of tire pressure are the same for any vehicle tire, regardless of type. The pressure inside the tire has to apply force across the contact patch of the tire in order to support the weight of the vehicle. Any vehicle, regardless of type, will have a prescribed pressure needed to support its weight on the appropriately sized tire.

Tire pressure is generally calculated according to the type and construction of tire and the weight of the vehicle, regardless of its powertrain. Electrified vehicles, however, are often equipped with "low rolling-resistance" tires, which may require higher or lower pressures based on their particular construction. The tire pressure and tire size listed on the driver's door label should be observed."

Toyota Canada

"No — the changes in altitude that most drivers experience are relatively small. If you check your tire pressure on a monthly basis with a reliable gauge and ensure that it conforms to the vehicle manufacturer's specifications, you should be okay."

Jonathan Scott, Technical Expert, Toyo Tires

"Most TPMS sensors run on lithium-ion batteries, designed to last 5-10 years. Still, TPMS sensors need regular checkups. The most common issues are corrosion, damage, and run-down battery life. Our climate plays a significant role too, as the road salt used in winter conditions may accelerate the rusting and failure of a TPMS sensor."

Nico van Wieringen, Operations Manager — OK Tire, Parksville, B.C.

Justin Pritchard is a Sudbury, Ontario based automotive journalist and award-winning presenter, photographer, videographer and technical writer. Every week, Justin uses his keyboard, voice and cameras to share his latest automotive reviews and discoveries with his audience, via multiple Canadian television programs, print and online publications.

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