It's right there in the name: direct TPMS. It gathers accurate pressure data directly from the tire valve via four dedicated sensors, reporting pressure information in near real time. Indirect TPMS, on the other hand, uses the ABS system to approximate tire pressure, and motorists must drive a substantial distance before an alert will be generated.
As the debate over direct and indirect TPMS technologies continues globally among regulatory, consumer and industry groups, one thing is clear: Consumers, when given the choice, express a preference for the direct TPMS scenario. Research undertaken by fast.MAP on behalf of Schrader has revealed that 69% of drivers do not wish to undertake the responsibility of manually resetting an indirect TPMS system. But, because of the absence of pressure sensors, a vehicle equipped with indirect TPMS requires the device to be recalibrated by the driver after tire pressure is modified or a tire is changed. This puts a level of control in the hands of the driver, something that is not the case with other critical safety functions in the vehicle such as air bags.
Additionally, in order for indirect TPMS to work effectively, all four tires must be inflated to the correct recommended pressure and be under optimum conditions. This seems like a defeating proposition for consumers, because the very reason they see the value in TPMS is to help them maintain the tire pressure to begin with. Similarly, indirect technology requires the consumer to install specific tires when replacing the originals in order to operate properly with the system. Last, if all four tires are similarly low in tire pressure from neglect (a common problem) or other reasons, an indirect system will not trigger a warning alarm. When all four tires are low, the tires wear quicker on the edges and the car is unsafe to drive, unstable and more likely to roll over; has less traction on wet roads; takes longer to stop; and uses more fuel. With so many variables about indirect TPMS that leave your brand vulnerable to dissatisfaction and warranty issues, direct TPMS just makes sense–for consumers and for you.