Tire Pressure Monitors

How accurate are electronic tire pressure monitoring systems? My dashboard digital readout usually reflects 3 or more pounds less than psi taken with various manual gauges (cheapo, expensive, digital). Which should I believe?

I consider mine to be accurate within + - 2 psi. + - 3 might be realistic as well. I read your post to mean that all four sensors read about the same amount low which is not likely.

depends. I’ve found the ones on my car to be accurate to within 1 pound. I would not extrapolate this to mean that all of the monitors on all models of my car are that accurate, however - I just got lucky.

I think mine are within one or two #. Not a big problem since pressures change with tire temps. anyway.

When I increase the psi so that the dashboard digital readout reflects GM recommended 30 psi front and 32 psi rear when cold, the manual gauges show about 33 and 35 respectively. And the ride gets much rougher. Can the monitors be checked or recalibrated? Also, the tires are Michelin Pilots, and my previous experience with Michelin is that they last for 50K miles, but the ride is harder than most.

The TPM on my van monitors the air pressure. I do not know how much leaway they allow.