TPMS sensors

[DS80]

Good evening all.

Does anyone know how the tpms sensors work? In terms of, do they have a sensor on the inside of the tyre valve, or is their another way?

Dan

[Clan]

Originally Posted by DS80

Good evening all.

Does anyone know how the tpms sensors work? In terms of, do they have a sensor on the inside of the tyre valve, or is their another way?

Dan

sensors disappeared around 10 years ago.. there are toothed wheels and a sensor which give about 40 pulses per wheel rev.. it compares all 4 wheels and any differences to work out how much your tyre pressures have gone up or down.

[DS80]

Ahh ok. Many thanks. That explains why all the 2nd hand wheels im seeing, have a normal tyre valve 👍

[Philip Fisher]

Originally Posted by Clan

sensors disappeared around 10 years ago.. there are toothed wheels and a sensor which give about 40 pulses per wheel rev.. it compares all 4 wheels and any differences to work out how much your tyre pressures have gone up or down.

Not exactly true. Early SPA cars had direct TPMS with sensors on the back of the valve. So on the SPA platform the switch from sensors to the system you describe above was 7 years ago.

[Philip Fisher]

Originally Posted by DS80

Ahh ok. Many thanks. That explains why all the 2nd hand wheels im seeing, have a normal tyre valve 👍

The valve looks identical from the outside. Inside there is a small transmitter and battery. It is about 200 quid for a set of 4 from Volvo.

You can tell if you car has sensors (direct TPMS) or uses the ABS sensors (indirect TPMS) by looking at your tyre display in the main screen. Actual pressures mean a direct system. Red and green dots mean an indirect system.