Correct Tire Pressure?

[jason510]

I did a search for this topic and all kinds of threads show up but none with the exact info I'm looking for. So, I took my car in for oil change/rotation at the dealership. I drove it into the service drive about 10am and they were done about noon. It was about 75-80 degrees or so.

I checked the tire pressure the next morning (it was 65 degrees inside my garage) and all four tires were set to 29-28psi. As we all know, our cars call for 33 front/32 rear cold tire pressure. I still have the crappy Goodyear F1 summer tires on.

I'm thinking they adjusted to 33/32 when doing the oil change when the tires were still warm? My thinking says that they should have set PSI to around 37-38 to account for warm tire pressure. My first inclination is to add air to the suggested tire pressure, but I'm also wondering why a tech at a large dealership would adjust to this pressure in the first place.

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[MoodySara]

A simple answer is that the tech used a crappy, uncalibrated tire gauge.

Your guess about setting them while hot is also a strong possibility.

I'd just wait for the tires to cool to ambient in your garage and reset them.

 

[DRuby]

I did a search for this topic and all kinds of threads show up but none with the exact info I'm looking for. So, I took my car in for oil change/rotation at the dealership. I drove it into the service drive about 10am and they were done about noon. It was about 75-80 degrees or so.

I checked the tire pressure the next morning (it was 65 degrees inside my garage) and all four tires were set to 29-28psi. As we all know, our cars call for 33 front/32 rear cold tire pressure. I still have the crappy Goodyear F1 summer tires on.

I'm thinking they adjusted to 33/32 when doing the oil change when the tires were still warm? My thinking says that they should have set PSI to around 37-38 to account for warm tire pressure. My first inclination is to add air to the suggested tire pressure, but I'm also wondering why a tech at a large dealership would adjust to this pressure in the first place.

Some web pages indicated a 1 psi loss for a 10 deg temp drop. Start by estimating the warm tire pressure. 120 deg is a very hot shower temp. I wouldn't expect tires that warm so maybe 100 deg. Cooling down to 65 deg would drop 4 psi.
I wouldn't expect rocket science calculations from an oil change tech so best is doing it right by doing it yourself.

 

[gtman]

I'm also wondering why a tech at a large dealership would adjust to this pressure in the first place.

Because he probably was someone who was just fired from Jiffy Lube for not meeting their standards.

Just fill your tires to proper psi when cold. Voila.

 

[DRuby]

Here's a link for a discussion about tire pressure changing between being set while on the lift and checked while on the ground.
https://community.cartalk.com/t/tire-pressure-on-the-lift-on-the-ground/1980

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