What are the differences between direct and indirect tire pressure monitoring systems?
Direct TPM systems directly measure the tire temperature and pressure via a sensor that is installed on the wheel. Indirect TPM systems indirectly measure air pressure. The most prevalent indirect TPM systems in use today utilize anti-lock braking systems (ABS) to measure the difference in the rotational speed of the four wheels. A wheel that is rotating faster than the others infers that wheel has lower pressure than the other wheels.
