[scottkeen]

FWIW, I have my TST 507 TPMS alerts for the trailer set to:

Low Pressure alert = 90 psi (10% below 100 psi)
High Pressure alert = 125 psi (25% above 100 psi)

The 10% low and 25% high alert thresholds is what the TST 507 user manual recommends.

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Sidebar: The TST 507 TPMS alerts for my 2007.5 Dodge Ram 3500 DRW truck are set to:

Front
Low Pressure alert = 58 psi (10% below 65 psi)
High Pressure alert = 81 psi (25% above 65 psi)

Rear dually
Low Pressure alert = 54 psi (10% below 60 psi)
High Pressure alert = 75 psi (25% above 60 psi)

I didn't know what pressure to fill my rear tires to, the sticker on the inside of the door says "Front = 65 psi, Rear = 40 psi normal load, 65 psi max load" so I figured 60 psi for the rear was some compromise between 40-65. What do you have your rear truck tires filled to?