TPMS sensors monitor tire pressure in real time and alert the driver through warning lights. There are direct, indirect and hybrid types, with the direct type providing accurate readings but at a high cost, and the indirect type costing less but not measuring air pressure directly. TPMS improves safety, extends tire life and improves fuel efficiency, preventing handling and braking degradation due to insufficient tire pressure.
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Table of Contents
1. What is TPMS?
The TPMS system with Tire Pressure Sensor (TPS) provides real-time sensing of tire pressure and alerts the driver in the form of dashboard warning lights, pictograms or pressure gauges. TPMS systems first appeared in some luxury and high-performance vehicles in the 1980s or early 1990s before being widely adopted. Since the early 2000s, TPMS has been a mandatory feature on new vehicles. Low tire pressure triggers a warning light on the dashboard to alert the driver to a potentially dangerous situation.
Tire pressure has a very real effect on vehicle handling and braking, and can also reduce fuel economy due to increased rolling resistance. Under-inflated tires will increase fuel consumption, and under-inflated tires will have excessive sidewall flex, leading to erratic and dangerous handling. In addition, increased rolling resistance and friction can cause tires to overheat and wear out faster, making a blowout at highway speeds very likely. It is estimated that as many as one-third of all cars, trucks, minivans and SUVs on the highway use under-inflated tires. It is estimated that tire failures due to underinflated tires result in 40,000 accidents, 33,000 injuries and 650 deaths annually.
2. TPMS types
There are three main types of Tire Pressure Monitoring Systems (TPMS) currently offered:
Direct TPMS:
Direct systems use actual sensors to communicate with the vehicle’s on-board receiver to monitor pressure and temperature from inside the tire.
Indirect TPMS:
Instead of using actual pressure sensors inside the wheel to monitor a single pressure, indirect systems actually use the vehicle’s ABS system to measure the rotation speed of each tire. A slight difference in tire pressure can cause one or more tires to rotate at a different speed than the others, which the system detects and causes the TPMS indicator light to illuminate. Defective wheel speed sensors or driving in wet conditions can also cause the TPMS indicator to illuminate on such systems.
Hybrid TPMS:
The internal tire sensors work in conjunction with the wheel speed sensors to help tell the driver (via the dashboard indicator) which tire is underinflated.
2.1 Indirect TPMS
Indirect TPMS usually relies on wheel speed sensors used in anti-lock braking systems. These sensors measure the rotational speed of each wheel, which the on-board computer system compares to other vehicle operating data such as vehicle speed. Based on the rotational speed of each wheel, the computer interprets the relative size of the vehicle’s tires. When a wheel begins to rotate faster than expected, the computer calculates that the tire is underinflated and alerts the driver accordingly. Therefore, an indirect tire pressure monitoring system does not actually measure tire pressure. It does not process the measurement electronically like a tire pressure gauge. Instead, the indirect pressure monitor simply measures the tire’s rotation speed and sends a signal to the computer, which activates an indicator light when a problem occurs during rotation.
Advantages of Indirect TPMS
- Relatively inexpensive compared to direct TPMS
- Less overall installation and maintenance than direct TPMS
Disadvantages of indirect TPMS
- May become inaccurate if larger or smaller tires are purchased
- Tire pressure measurement may be unreliable when tires are worn unevenly
- Needs to be reset after each tire is inflated
- Need to reset after daily tire rotation
2.2 Direct TPMS
Direct TPMS uses pressure monitoring sensors within each tire to monitor specific pressure levels, not just wheel speed data from the anti-lock braking system. The sensors in the DPM system also provide tire temperature readings.
The direct tire pressure monitoring system sends all of this data to a central control module where it is analyzed and interpreted, and if the tire pressure is lower than it should be, it is transmitted directly to the instrument panel, where an indicator light will come on. Direct tire pressure monitors usually send all this data wirelessly. Each sensor has a unique serial number.
Advantages of Direct TPMS
- Provides actual tire pressure readings from internal tire measurements;
- No errors due to tire replacement;
- Simple re-synchronization after changing tires;
- The battery in the sensor usually lasts about 5-10 років.
Disadvantages of Direct TPMS
- Overall price is more expensive than indirect TPMS.
- The battery is not serviceable; if the battery is depleted, the entire sensor must be replaced.
- Sensors are easily damaged during installation/disassembly.
3. Benefits of TPMS
The primary benefit of TPMS sensor is to provide drivers with vital tire pressure information, letting them know when their tires are underinflated and preventing dangerous situations from occurring. Improperly inflated tires can affect handling, braking performance and fuel economy, and can lead to tire blowouts at high speeds.
Safety
Under-inflated tires have poor handling, poor braking, unpredictable cornering, and are very unstable, so it is important to read tire pressure accurately.
Tire Wear
Underinflated tires wear out at the edges and shoulders because their footprint on the road is deformed by the weight of the vehicle, and this wear can lead to a reduction in the life of the tire tread. Worse yet, under-inflated tires generate more heat, which damages the integrity of the tire itself, leading to premature wear of the steel belts and fibers, and possibly tread separation.
Fuel Efficiency
Underinflated tires increase rolling resistance and friction, causing your car’s engine to work harder, which in turn affects fuel economy.
Conclusion
TPMS sensors are an indispensable safety feature in modern vehicles, helping drivers identify potential problems in real time by monitoring tire pressure and temperature. Whether they are direct, indirect or hybrid TPMS, they play an important role in enhancing driving safety, extending tire life and improving fuel efficiency. Proper maintenance and use of TPMS sensors not only enhances the driving experience, but also prevents accidents caused by tire failure, providing a safer driving environment for drivers and passengers.
