Our Anti-Theft Airchecker TPMS caps work on a very simple principle. They are based on a selection of high pressure springs that are manufactured to specific tolerances. They range from 26psi (1.8bar) to 80psi (5.5bar) to match the most common pressure settings for cars, motorcycles, commercial vehicles, trailers and caravans.
 
When the tyre is correctly inflated the spring pressure allows a green indicator to be clearly visible in the viewing window, showing that the tyre pressure is correct (as shown on the right).

If the pressure reduces by 15% (around 4psi) the green indicator is replaced by a yellow one, giving a warning that the tyre pressure is reducing (as shown on the right).

If there is a 30% (around 8psi) or more reduction in tyre pressure then a red indicator becomes clearly visible, giving a clear warning that the tyre pressure is now dangerously low (as shown on the right).

This system is both reliable and affordable and will give an early indication of a potentially dangerous reduction in tyre pressure. For further details visit our FAQ page here.

This is just as important as the other 4 (even if it's a space saver it's still requires air), should you ever need to use it in an emergency you need to know it's ready for the job - it's no good it being flat when you need it most! If your tyre pressures are different from the front to the rear, have the spare set at the higher pressure (excluding space savers as they usually run at higher pressures - check to see what pressure it requires).