When will the TPM light up?

I am wondering how much air the tire pressure has to lose in order to activate the TPM warning light? Are all four TPM modules set to detect the same X PSI to activate the warning system?

I always stay with the door label for 35psi at front and 38psi at rear. If, for example, all 4 TPM modules are set at 28psi, then it will activate the warning light when the front lost 7psi (20%) from 35 to 28. But then if the rear tire pressure drop to 28psi, it means a 10psi difference (a 26% lost of pressure compares to only 20% at the front).

Can someone enlight me with a possible answer?

 

Thanks a lot. That's the exact info I was looking for. :thumb: