The Acura Link app shows that I have 39 psi of pressure about three hours after parking the car. How much pressure are you running in your cars?

 

as you found out, driving the car will heat up the tires, spiking the PSI.
Measure the car when its cold....6 hours of no driving and it will be in the correct range as indicated as the door placard.

 

Cold, my PSI is 34PSI all around, when the tires are warmed up they jump to about 36. For reference, I have the A Spec so I have the 20" wheels.

People have noted that their tires come overinflated when they first purchased the car, that might be the case of your vehicle.

 

Parking in the sun will also raise the tire pressure. I've seen as much as a 3 psi difference between right and left side when one's in sun and the other in shade.

 

OoO forgot about that pesky sun.

 

 

My PSI was set at 36 front and rear and I wasn't real happy with the feel of my RDX. It wasn't bad but it felt more like a sports car rather than a soft ride. The dealer suggested lowering the PSI to 34 and so far I see a huge improvement.

 

 

Do your valve stems have green caps? If so, then the dealer "supposedly" filled them with nitrogen.

I bought mine in Tucson also, and they have green caps, and were filled to 40 lbs. which seems highly unlikely if they are filled with nitrogen....especially considering the high number of owners who have reported them being at 39-40 lbs on delivery.

 

 

Not a valid gauge at all since nitrogen will expand/contract with temperature.

From: https://m.tirerack.com/tires/tiretec...jsp?techid=191

 

 

 

SUMMARY: NITROGEN IS GOOD but not that good. — there is no true or real benefit in using nitrogen over compressed air. However, keep in mind that if you plug the benefits of nitrogen over air in each category and apply scientific reasons and graphs you’ll see that there’s an absolute benefit to using nitrogen each and every time over every category.

However, this benefit is negligible or tiny when weighed in the real world. My opinion is that if someone offers you nitrogen of course take it. But don’t go out of your way to get it. Also, no one has mentioned the idea “why” hot tires increase in pressures.... => normal compressed air causes condensed gas water vapors to solidify into water in the bottom of storage tanks which gets into your tires. This creates heat and friction and expansion later when the water heats back into gas and expands as the tires performs. Not an issue with nitrogen.

Cooler running temperatures: When air is pressurized, the humidity in it condenses to a liquid and collects in the air storage tank you use at the local gas station. When you add compressed air to the tire, the water comes along for the ride. As the tire heats up during driving, that water changes to a gas, which then expands, increasing tire pressure. Because nitrogen is dry, there is no water vapor in the tire to contribute to pressure fluctuations.