TPMSDirect Frequency Asked TPMS QuestionsWhat is Indirect TPMS?Indirect TPMS are ABS-based, meaning that wheel speed sensors are installed on a vehicle's anti-lock brake (ABS) system. Wheel speed sensors measure tire pressure data by tracking the rotational speed of each tire. The basic premise of Indirect TPMS is that an under-inflated tire has a smaller radius and thus spins at a higher RPM compared to a normally inflated tire. An overinflated tire has a larger radius and spins as a lower RPM compared to a normally inflated tire. Wheel speed sensors translate rotational speed data into tire pressure data and then relay the information back to the driver. Several Audi vehicles implement the Indirect TPMS method.  |