Tire Pressure Question

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This is a hypothetical situation. Let's say you have a vehicle that comes into a shop for routine maintenance. The vehicle is equipped with an indirect TPMS system which requires a reset (calibration) if the pressure is adjusted on any tire or if the tires are rotated. The routine maintenance work is completed after 30-45 min and the tires are still "hot." You proceed to set the tire pressure and you are faced with one of the two options: Option #1) Set the tire pressures to the cold spec (door jamb label) and perform the tpms reset. This option will allow for the thresholds to be set correctly, but the actual tire pressure will be a few pounds low once the tires cool down. Option #2) Set the tire pressures 2-3 lbs above the cold spec. This option will result in the thresholds being set incorrectly, but the actual tire pressure should be correct (or very close) once the tires have cooled down. Which option would you choose and why? Note: skipping the TPMS reset is not an option as the vehicle is extremely sensitive.
 
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Question is too vague. Would need to know year, make, model, mileage of vehicle. Would need to know tire size, make, model and mileage.
 

The Critic

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Originally Posted by BretK
Question is too vague. Would need to know year, make, model, mileage of vehicle. Would need to know tire size, make, model and mileage.
I don't see how any of those items are relevant for this question. We are working with a sensitive indirect TPMS system. Tire size has no factor in this situation.
 
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The Critic

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Originally Posted by Snagglefoot
Also, are you using a hand held reset gizmo or doing it by adjusting the pressure until the horn sounds for each corner.
This particular system has a reset option in the vehicle's cluster.
 
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Originally Posted by The Critic
Originally Posted by BretK
Question is too vague. Would need to know year, make, model, mileage of vehicle. Would need to know tire size, make, model and mileage.
I don't see how any of those items are relevant for this question. We are working with a sensitive indirect TPMS system. Tire size has no factor in this situation.
If you want a complete answer, complete info is necessary. The question is too vague. Or the answer might be "It depends ...."
 
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I would diffinately use #2. Setting the tire pressure to 2 psig over due to the tire being warm is the way I go. Don't over think this simple question. ed
 
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When I was turning wrenches I would add a couple PSI to hot tires. Wasn't an exact thing, but it got it closer to the proper cold temp. Even now on my car I wait until the end of the day after my car has sat for 9 hours to slowly drive it into the shop and set pressures.
 
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When I ran a tire shop the guys in the back knew to increase tire pressure in the winter. This also applied to new tire install as the shop is ~60 degrees but it's 10 outside. I was there pre-TPMS so we made sure to educate the customer.
 
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It doesnt matter with indirect tpms. A reset, whether hot or cold just sets a baseline for the system to detect rotation speed differences between the tires. 4 tires at a cold 32 psi will all slow down equally as the temp rises to 34 as the car is driven. As for having to adjust the pressures on a hot car I'd just inflate the three lowest tires to the one with the highest pressure as long as it is within 3 to 5 psi of the cold spec.
 
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I know nothing about this stuff. Seems that option 2 is the most correct. Page 87 of this tech bulletin linked below recommends adjusting the pressure 2 - 4 lbs. above the placard recommendation for tires that are not cooled down to "room temp" of 72 degrees F. https://www.pearsonhighered.com/assets/samplechapter/0/1/3/4/0134073657.pdf Could an infrared temperature gun be calibrated to use in this situation, assuming the tires are not in direct sun??
 
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I always add 2-3 PSI when I air up my tires if they are hot or cold That is for eventual leakage and colder weather
 

Nick1994

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Originally Posted by CharlieBauer
Set TPMS at correct PSI. Then add 2-3 PSI to ensure tires are at right inflation to be driven.
+1
 
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As mentioned, indirect systems typically monitor rotational speed differences, the actual pressure is irrelevant. So no need for a reset. I have two vehicles with this system. As for the exact pressure to set them at. If you feel it needs to be exact, then just wait until the next day and adjust them when they're cold to whatever pressure you desire.
 
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Set the tires higher than the cold spec. I once tried to explain to a young apprentice technician why setting the tires to the cold spec, inside a heated shop + 15*C (60*f ), with outside winter temps around - 25*C ( -13*f ), was a bad idea. The tire pressure would drop roughly 7- 8 psi as the tire cooled down to outside temperatures. Enough to trigger tpms sensors, and be a potentially serious safety problem.
 
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My tires goes up as 5-6 PSI when it becomes hot. Adding 2-3 PSI is quite low on a hot tire.
 
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