A Guide to Tire Pressure Monitoring Systems (Part 3)
Welcome to part 3 in our series on Tire Pressure Monitoring Systems. For part 1, please click here, and for part 2, please click here.
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Indirect Monitoring Systems
Indirect systems use the car’s anti-lock braking system’s wheel speed sensors to determine rotational speed of one tire and compare it with another on the same vehicle. If one of the tires has a lower pressure level, the circumference changes enough to roll at slightly more revolutions per mile than the other 3 tires. Reading the same signal that supports Anti-lock braking systems, car manufacturers’ have programmed another function into a vehicle’s on board computer to warn drivers when one of the tires is running at reduced or increased inflation pressure compared to the other 3.
Unfortunately, indirect TPMS have several demerits. They will not tell you which tire is low or higher in pressure, and will not warn you if all the four tires are losing pressure at the same time at the same rate. Additionally, they sometimes generate frequent false warnings. This may occur when the tires spin on icy, wet and snow covered surfaces. In these cases the false warnings may train you to disregard the system’s warnings negating its main purpose completely.