newworldjj

I bought 2015 CPO ES350. The tire pressure info says 37 cold pressure. Dealer service advisor says that is normal range. Should I leave this alone or let some air out?

pab12

>Should I leave this alone
Depends, do you want a softer ride or do you like the sense of control that higher air pressure brings? It's purely a matter of choice, 37 lbs cold is in the "performance" level not the "touring" one.
===================================
Angle parked in a parallel universe

newworldjj

Thanks, pab12, for your reply. I had no idea pressure could be set as more than the factory recommendations. Since dealer set it as is, I'll leave it alone for now. See how I like it this way.

mcomer

PSI varies with ambient temperature and driving speed. More meaningful is
that all four tires are roughly the same, less then 5 PSI different. If one gets
way off you should check for a puncture or less often, a bad valve. Not shown
but worth a check is the pressure in the temporary spare. Your ES has a panel
in the driver's door opening that calls for 33 PSI. Since the low tire light will come
on at about 28, it is easiest for the shop to run them up a bit to save you from
coming in or calling all upset over a light you may think is more critical than it is.

sderman

If you want a comfortable "Lexus ride:" I would change the pressure to 33 psi as recommended by the manufacturer for the vehicle. 37-38 psi gives a harsher ride. My past ES350 (2007) had the recommended pressure at 30 psi, so 33 is more than sufficient.

newworldjj

Thanks, mcomer and sderman, for your reply. I'm incredibly grateful for your information.

Poppa

Personally I would let some air out.. I keep my air pressure right around 32 psi. Seems to help give the car a bit of a softer ride.

Roland

hisstojay

I totally agree with Sderman, leaving it as recommended pressure is best and safe. All my cars have always been set at recommended psi.

newworldjj

Thanks, Roland & hisstojay, for your advice. I'm going to set it at 33 per factory recommendations.

jfelbab

While 37psi is 5psi over the manufacturer's recommendation, that is not necessarily a bad pressure reading depending on where and when the pressure was read.

The manufacturer recommends tire pressure be set when the tire is cool, typically first thing in the morning before the vehicle is driven. Say you set the pressure to 32psi at that time. You've been driving for a while and check the pressure in the afternoon when the outside temperature is now 80-90°F. Now the tires are hot and your pressure could easily be 35-37 psi.

Whether you run air (78% nitrogen or you use pure nitrogen ~96% nitrogen, your tire pressure will change by 1 psi for every 10°F in temperature change. Nitrogen use doesn't alter that, this is a law of physics affecting all gases.

Say you set your tires to 32psi at 7am when it is 50F. You check the pressure at 2PM and it is now 90° F. the pressure would now read 36psi. Drive around for an hour on roads that are in the low 100's and the tires will now read 38-40psi. Don't drop the psi in a hot tire to the factory recommended value. Wait until the tire is cool to set the pressure and check it regularly. Tires handle over inflation much better than they handle under inflation. Consider your lowest expected temperature when adjusting your tires.

I used to live in the north and would to wonder why the dealer would set the pressure to 37psi at times. It was because the temperature in the garage was 68°F and the outside temperatures were often in the teens. When these tires were checked at my home in the morning they would usually read about 32psi. Sometimes the overnight temps would drop to below 0. I'd then be riding on a tire that likely would be 28-30psi. Just be aware that the tire will achieve maximum traction, handling and comfort at the manufacturers recommended psi.

I set my tire pressures based on my driving conditions. I check them monthly and adjust them for the expected seasonal temperature changes. Based on where I live now and the kind of driving I do, I set my tires to 33psi cold. I use regular air as I am a long way from any Nitrogen. More important is the regular checking and adjusting the tire pressures.

newworldjj

Thanks, jfelbab, for your detailed response. I read in this forum some members keep a air compressor in their garage and I can guess why now. Mine is 37 in the garage in the morning by the way.

jfelbab

Oh yeah. I bought this compressor a few years back. Really rugged and low maintenance.

Sulu

In addition to what jfelbab said, we must remember that the recommended pressure recorded on the door jamb is the automaker's recommendation for a comfortable ride, for the original tire; that recommended pressure will be lower than the maximum tire pressure printed on the tire's sidewall.

And yes, it may be dangerous to be on the low side of tire pressure. Those who remember the Ford Explorer - Firestone tire problems and recalls may remember that a cause was recommended tire pressure that was too low. Low tire pressures are more prone to overheating than higher tire pressures, and the overheating of the Firestone tires on those Explorers contributed to the separation of the tread from the tires, causing high-speed rollovers.

newworldjj

Thanks, sulu. These are so useful information to have.

jfelbab

One additional thought. Many of the cheap pencil tire gauges are not very accurate. They often will change over time and temperature. Best to get a good tire gauge and take care of it. I prefer one of these digital gauges Accutire MS-4400B or MS-4021B, or Joe's Racing 32307 analog gauge.