I searched but did not find this answered. Does anyone know how much of a psi drop will activate the TPM warning in the dash? I hadn't checked my tires for about 2 months (I know, too long). I drove up to Asheville, NC on Saturday evening and ended up staying overnight with the car parked outside. When I started the car up Sunday morning, all 4 tires tripped the warning. When I got home, all 4 tires were right at 31 psi. I inflated them to 36 psi and reset the TPM and all is fine. But, it would be nice to know exactly how much variation trips the light. TIA.

 

I do not have access to the MINI TIS right at this moment but from memory a 10% drop is all that is needed.

Please note a 10 degree drop in temperature will cause approximately 1 psi drop in pressure.

So lets say you checked the tires at 5pm with an outside temp of 80 degrees then you drive to the mountains and the next morning you get up and the outside temp is 40 degrees Now check the tires and you will see them at about 31-32 psi. 40 degree temp drop drops the pressure approximately 3.7-3.9 degrees.

This could be part of your problem. I.E. the tires were slightly low before you left but not enough to trip the sensors and then with a temp drop it pushed them below the trip point.

 

Thanks. A 10% drop isn't much to trip the warning.

 

And that is why many of us have problems with the system in the fall and the spring when there is a wide range of temps from day to day. There have been times in the past 4 years where I have had to reset it 2-3 times in a week.

There is also a minimum pressure as well which if i remember correctly is like 25 PSI where you can not reset the monitor.