I live in Phoenix AZ where it gets very hot during the Summer. The Lexus Door recommended PSI for my RX350 is 32. One Lexus dealership says should have 28 PSI and a second says 36 PSI. I know the temperatures can affect tire pressure. Of the three 28, 32, or 36 is correct. Or perhaps change when it is cooler than hotter?

 

Running at lower pressure than recommended will heat up the tire even more. The least heat buildup actually occurs when the tire runs at the maximum shown on the tire’s sidewall (the pressure at which the tire receives its maximum load rating) but ride quality will suffer slightly and traction is usually lower than when the tire is run at the recommended pressure shown on the placard pasted on the car, which on mine (with the 20” tires) is 33 psi. I run mine at about 35 psi cold.

For reference, one contributing factor to the Ford Explorer rollovers some 25 years ago was that Ford lowered the recommended tire pressure for greater comfort while increasing the weight of the vehicle, cutting the tire’s safety factor down considerably. So that when the vehicle was run in the southern US in the summer, at high speeds, the tire sometimes failed prematurely.

 

The consensus of this board is to follow the sticker on the door. I personally don't do much with adjusting frequently as the temps change except for like today when it was below zero and one tire caused the light to come on at 28 pounds so I added some. This spring, when it warms up and I'm wondering why the ride is so harsh, I'll probably remember to let some air out

 

I think overinflate is better than underinflate.

I myself inflate the tires 10% higher than what prescribed on the sticker (36 vs 33). The ride is just a bit firmer but I feel I can control the vehicle better.

I check and adjust tire pressure monthly, early morning the first Saturday of the month.

 

For city driving plus or minus 2 psi is no big deal for tire pressure. If going on a long trip, you want to be at or slightly above the recommended number. This will put the car at maximum stability at highway speeds.

 

Go by sticker. The sticker shows required tire pressure for your car, cold tires - prior to driving the vehicle. If it is hot outside (your case) and your car is parked in cooler garage, you need to move it outside to get a correct tire pressure before adjusting it. I personally keep tire pressure just 1-2 psi above stated on the sticker. If you overinflate tires, they will wear out fast in the middle, and this is dangerous for vehicle handling, and is not rectifiable. It is more dangerous, than worn out edges of the tires as your car main contact with the road is the middle part.

 

Manual says door jamb psi on oe tires were taken when the vehicle had sat overnight or more then 4 hours.

 

Moving the car outside and waiting for it to reach outside temperatures to adjust tire pressure? No. Not necessary and it can result in uneven pressures. The instructions merely mean to set tire pressure before driving the vehicle, when tire temperature really escalates.

Garages here typically aren’t cooled, they’ll still be quite warm. 100 degrees in summer afternoons…

 

The recommended Tire PSI should be 33 PSI (COLD), which is stated on the Placard.

I've been playing with the pressures going 1-2 PSI over the spec and I have noticed 33 PSI (COLD) is best.

Either way, going over by 1-2 PSI will not compromise ride quality and performance by much.

As you drive, the tire expands and the PSI will go up natural (up by 5 PSI!).

 

I set my tire pressure so that it is 36 sometimes 37 when the tires are warm. I set the cold pressure to achieve the warm pressure.

 

Morning temps were 5 degrees this week. My wife texted me the TPSM light came on. The psi had dropped to ~29, so just filled up to 33 psi. Interesting that none of our other 3 cars had the TPSM light come on.

 

It is not unusual for the seal strength between the tire and rim be different for different cars. They all leak air over time but do so at different rates. Check your tire psi at least twice a year.

 

Uneven pressures especially if one side of the car gets full sunlight which will further warm and increase the pressures on that side.

 

Overthinking to the max.

First thing in morning, before you drive, pump to the placard.

That is it.

 

The placard is a good starting point normally about 33 psi. Add 2 or 3 psi if you live up north for winter. The psi will decrease over time. It is normal for tires to leak some air. Do not panic over a small amount of leakage.
I add about 2 psi 2 times a year to my tires. Very easy.