Tire Pressure Question
 

Driving my 2021 350 ES on original tires with 13,000 miles on them. When driving the other day, I randomly checked my tire pressures by the meter on the dash. 35 PSI. Car drives beautifully and I thought all was well. But next day, I noticed the posting inside the door says 36 PSI COLD. That would be about 40 PSI when the tires heat up. Isn't that a bit much and harmful for the tires? Won't a pressure that high compromise the comfortable ride I'm enjoying at 35 PSI (warm) and 31 PSI (cold), which is what it is after overnight in the garage as I just checked? Am I harming the tires with 31 PSI COLD?

I would start by not relying on the readings from the tire pressure sensors; these can easily be off. Get the actual pressures by using a good gauge.
My understanding, and I'm no tire expert, is that the posted pressures are based on a lot of different things, not just comfort. You can deviate from that, but when you improve one aspect of the tire by adding or subtracting from the posted PSI, you affect other aspects. I would think that decreasing air pressure a bit would make any car's ride seem softer; adding more pressure would make the tire harder and lessen its shock absorbing capacity, giving you a harder ride.
I would try the car for a while at the posted pressure for a while, and then see how you like the ride when you increase or lessen it. I do not know how either of those would impact on the life of the tire.

In addition to tfischer's comments, on US sold tires there's a requirement that the maximum (safe) tire pressure be printed in some permanent form on the tire's sidewall. On my OEM Bridgestone TURANZA EL440 94V tires in tiny raised lettering 51 psi is the maximum pressure specified.

Also, if you check the Owner's Manual in chapter 8's "Tires and wheels" section you'll see for your 17 inch tires there's two "Recommended cold tire inflation pressure"s: 36 psi (250 kPa, 2.5 kgf/cm2 or bar) for 100 mph (160km/h) or less and 46 psi (320 kPa, 3.2 kgf/cm2 or bar) for more than 100 mph (160 km/h).

So, assuming you're a below 100 mph driver, a 36 psi cold inflation pressure that raises to about 40 psi when the tires heat up isn't a bit too much or harmful to the tires.

Trading off comfort for mileage. I like 35 cold.

34 cold is my favorite for noise and comfort

my TPMS sensors are exactly the same as when I measure with one of our tire gauges

running 40psi cold is not only not dangerous, but in fact better for high speed driving safety. A Porsche has a warning to not drive at high speed until PSI is raised from comfort pressure to high speed pressure which is something like 5psi higher

higher pressure gives more protection for the rims when you hit a bump especially with low profile tires. I run my wife’s IS350 FS at about 38psi cold because it has 19 inch wheels with 35 series rubber

I find 32 cold (36 hot) is the softer ride I prefer. So am I harming the tires or causing them to wear prematurely by not doing 36/40?

Go by the way the tires wear straight across. If you see the outsides wearing more than center then raise it. Also makes a difference in gas mileage.

Thank you.

The ES with noise reduction wheels heat up the tires and the pressure tend to rise, 35 to 38.

So if set cold at say 32PSI, then they heat up to 35-38. That sounds ideal to me.

All tires heat up and psi rises after driving

The door sticker on my 2020 ES350 UL says 35 PSI. It's amazing my TPMS readings and the readings on my digital gauge are within 1 pound of each other at worst. I keep everything at 35 but need to adjust at least twice a year due to changes in weather and temps. I never have the dealership change my tire pressure since they ALWAYS overinflate my tires by 4-5 pounds every time.

Both Lexus dealers here do that also and it’s annoying. Discount Tire inflates to door sticker PSI.

sinxe to many dealers do this there must be a reason, perhaps liability because driving over 100mph you should run higher PSI.

injust adjust my pressures after visiting the dealer myself, we keep an electric air punp in each car already.

No, inflate them to 35 when they are cold.

The reason most likely varies by locale. For example, there's a California Air Resources Board (CARB) Tire Pressure Regulation requiring California automotive service providers to "Check and inflate each vehicle’s tires to the recommended tire pressure rating, with air or nitrogen, as appropriate, at the time of performing any automotive maintenance or repair service." (The FAQ link on that web page does have an item on the conditions for a customer to decline the check and inflate service requirement.)