TPMS explained: how tyre pressure monitoring systems work

TPMS, short for tyre pressure monitoring system, is a system that watches the pressure in a car’s tyres while it is being driven and warns the driver when one runs low. It comes in two kinds. A direct TPMS has a sensor in each wheel, usually built into the valve, that measures the pressure and sends it to the dashboard, often as a figure for each tyre. An indirect TPMS has no sensors in the tyres; it uses the anti-lock braking system’s wheel-speed sensors to spot a tyre turning faster than the others, which is what an under-inflated tyre does. Either way, the warning is designed to come on only after a tyre has lost a substantial amount of air, so a TPMS is a safety net, not a substitute for checking pressures every month.

What is TPMS and why cars have it

A tyre can lose pressure slowly enough that the driver never feels it. An under-inflated tyre wears faster, grips less and runs hotter. A tyre pressure monitoring system closes that gap by watching for falling pressure while the car is moving.

India’s road transport ministry described the system in exactly those terms when it added a TPMS specification to the Central Motor Vehicles Rules in July 2020: a system that monitors the inflation pressure of the tyres, or changes in it, while the vehicle is running, and passes that information to the driver.

Direct vs indirect TPMS

Direct TPMS uses a pressure sensor in or on each wheel, typically part of the valve. Michelin and Hyundai both describe it as giving real-time readings for each tyre, which the car shows on the dashboard, either as a warning light or as a picture of the car with each tyre’s pressure. The sensors run on batteries; Michelin gives their typical life as five to seven years, and notes they are exposed to corrosion, shocks and high speeds.

Indirect TPMS works out pressure without measuring it. When a tyre loses air its rolling diameter shrinks slightly, so it turns faster than the others. The system reads the wheel-speed sensors already used by the ABS and stability control and warns when one wheel’s speed drifts. Hyundai notes this costs less, as no extra sensors are needed, but is less precise and may not catch slow leaks as well.

	Direct TPMS	Indirect TPMS
How it measures	Sensor in each wheel	Wheel-speed comparison
What you see	Often each tyre’s pressure	Usually a warning light only
Extra parts	A sensor in every wheel	None in the wheels
Weak spot	Sensor batteries and higher cost	Less precise; may not catch slow leaks as well

When does the TPMS warning light come on?

The international regulation for these systems, UN Regulation 141, sets the benchmark for cars. The warning must come on within 10 minutes of driving at 40 km/h or more once a tyre’s pressure has dropped 20% below its normal operating level, or to 150 kPa (about 22 psi), whichever is higher. For a slower loss affecting the tyres more gradually, it allows up to 60 minutes. The system must also show a separate warning if it develops a fault.

In practice, Michelin translates the 20% threshold as roughly 0.4 bar on an average car, and points out that by then the tyre is already under-inflated. That is why it still recommends a monthly check.

The light itself often looks like a tyre with an exclamation mark inside. Hyundai explains that a steady light normally signals low pressure, while a blinking light points to a fault in the system.

Is TPMS mandatory in India?

Not on every car, as far as we can find. The July 2020 amendment to the Central Motor Vehicles Rules set out a specification for tyre pressure monitoring systems on vehicles up to 3.5 tonnes that applies if one is fitted. India’s TPMS standard, AIS-154, follows UN Regulation 141 and covers passenger cars and light goods vehicles when they are equipped with a monitoring system; the main difference is a wider test temperature range of 0 to 50 °C.

The same 2020 amendment created a strong reason to fit one. A car with a tyre repair kit and a TPMS no longer needs to carry a spare wheel, which lets car makers supply a sealant kit in place of the spare. Our guide to run flat tyres covers the other way cars can do without a spare.

By comparison, Michelin notes that TPMS has been compulsory on new cars in Europe since 1 November 2014 and in the United States since 2007. If India makes it compulsory, we will update this guide.

Which Indian cars have TPMS?

It depends on the model and, often, the variant, so check the brochure or the specification sheet for the exact version you are buying. Hyundai Motor India says TPMS is standard on many of its new models. BMW India’s specification sheets list a tyre pressure indicator alongside run flat tyres. On cars sold with a repair kit instead of a spare wheel, a monitoring system is part of what allows that.

Add-on TPMS kits and smart tyres

If your car did not come with TPMS, kits can be added later; Hyundai notes that aftermarket systems exist, while recommending professional servicing for its own. Some tyre makers build the sensing into the tyre itself. JK Tyre, for example, launched passenger car tyres with sensors embedded inside in November 2025, made at its Banmore plant in sizes from 14 to 17 inches, which track pressure, temperature and air leaks. It describes them as an advance on the SMART tyre technology it introduced in 2019, which combined TPMS with cloud-based analysis.

Living with TPMS

• Keep checking monthly. The light warns of a large loss, not a small one. Our guide on how to check tyre pressure covers the routine, and the tyre pressure lookup gives makers’ figures for Indian cars.
• Tell the shop your car has TPMS when you change or rotate tyres. Michelin notes that after a change of tyre size, which can change the right pressure, the system has to be reset by a professional.
• Mind the spare. Hyundai notes that fitting the spare typically leaves that wheel unmonitored.
• Do not ignore a blinking light. It means the system cannot do its job until it is repaired.
• Nitrogen does not change any of this. See our guide to nitrogen vs air.