Trying to set a tpms system. How much should a 225-75-16 tire pressure rise from 60psi cold to ?hot?, assuming outside temp of 70*. On the tpms you set for cold pressure. It will alarm at 15% . I wanted to alarm at a recognized 55psi. So if I set to say 63psi then it falls 15%, that would be around 55psi, or close enough. BUT coming from the tire store today it alarmed as high pressure and showed 73psi as the tire warmed up. Best I can explain it.

You should factor in what summer temps are going to do to the pressure. I've seen my 11:22.5 go from 90 lbs to 122+

A good rule of thumb which I use is that for each 10 deg F rise in temperature, the tire pressure will rise 1 psi.

On my TST system, the defaults were minus 10% and plus 20%. For my rear tires , cold pressure 80 psi. The low alarm would go at 72 psi and high pressure at 96psi. I changed the high pressure alarm to about 104, because of driving in 100f temps. The side in the sun were just over 100psi, but the shady side stayed around 95 , 96 psi The high temperature alarm was defaulted to 160f. My tires were close to alarming that day as well. That temperature did agree with my infrared temp, I also checked a couple of parked trucks and there temps ranged from 170-180 on the driving sunny side. I’m much more concerned about low pressure than the highs, so I reset the low pressure alarm to 75 psi. Also the appropriate change for the front axle where I run 65 psi Ken

Side note, tires are rated at double what is stamped on the side - because they know heat and hard use will increase the temps inside the tire. 80 psi tire new should handle 160psi without blowing up. An older tire will blow up.

Op again. My tire traker is alarm at 15% low, 25% high, not changeable. Unit is advertised at +/- 2.7% pressure precision. So if I run cold tire pressure 60psi then: error of about 6psi either way. Only interested in low pressure, so if I set base pressure at 60 psi, alarm should sound at about 50psi considering error rate and 15%. But that means the high pressure could sound as low as about 70psi. Yesterday on a short drive with outside temp at less than 70* tire pressure went up to 74psi and high pressure alarm sounded. So on a hot day like Mex’s post, where do you set your base? Do you have to adjust all of your pressures thru out the day? Another’s rule of thumb would only be 3psi for a 30* temp swing?Where am I figuring wrong.

Cold tire pressure vs hot | Good Sam Community

Beverley_Ken
Explorer
Mar 16, 2019
On my TST system, the defaults were minus 10% and plus 20%. For my rear tires , cold pressure 80 psi. The low alarm would go at 72 psi and high pressure at 96psi.
I changed the high pressure alarm to about 104, because of driving in 100f temps. The side in the sun were just over 100psi, but the shady side stayed around 95 , 96 psi
The high temperature alarm was defaulted to 160f. My tires were close to alarming that day as well. That temperature did agree with my infrared temp, I also checked a couple of parked trucks and there temps ranged from 170-180 on the driving sunny side.
I’m much more concerned about low pressure than the highs, so I reset the low pressure alarm to 75 psi. Also the appropriate change for the front axle where I run 65 psi

Ken
Gonzo42
Explorer
Mar 16, 2019
A good rule of thumb which I use is that for each 10 deg F rise in temperature, the tire pressure will rise 1 psi.
MEXICOWANDERER
Explorer
Mar 16, 2019
You should factor in what summer temps are going to do to the pressure. I've seen my 11:22.5 go from 90 lbs to 122+

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