TonyC

bumpity. went to Discount Tires to get a small leak patched. they also rec'd 39psi for "longer tire life". hesitant in going up this high, but the OEM tires at 33psi are showing quite a bit of (relatively even) wear at only 15k mi.

should i bump to 35-37?

4TehNguyen

iTrader: (1)

overinflation causes abnormal center wear, under inflation causes abnormal edge wear

alsilverbullet

I guess I should read the manual but what is the recommended tire pressure? Mine read 32psi when cold and go up to 33-34 when warm with the exception of the spare which I believe stays at 32. Just the other day my low inflation light came on while on the highway and stayed on for a good 15 minutes & then went away. Is the spare under inflated thus causing the light to come on?

rominl

iTrader: (4)

i would not listen to discount tire. 39 is VERY high for 18s. like i said, i ran 40 on my 20s and i had premature center wear

rominl

iTrader: (4)

factory is 32 or 33 i forgot

i think if it's under 28 or so it will light up. just read the tire pressure data on the screen, you can see how low it is. i would start by checking the spare

Gojirra99

What psi are you running on your 22's ?

rominl

iTrader: (4)

38psi cold. the ride is huge difference from running 41psi

at 38, i risk a bit more on potholes, but i usually drive "known routes". and at 38, i still expect more center wear over time, but 35psi sounds a bit scary

19psi

tell you what guys, i run 39-41 psi on my 18's al lthe time and never have a problem with excessive center wear.

for your spares, keep them high, like 36 psi. they rarely get used, but they still slowly seep air while sitting in the trunk. if you keep it high, then it will be much longer before it sets the tpms light.

zzzzdoc

Is the factory suggested pressure for the LS600 18's the same 32 or 33. If so, mine also came with the pressure at 44, and I never thought to lower it. They're down to about 37-38 now with the cold weather. Do I need to lower them further?

Oh, and the massive P-Zeros on my Murci run at 45 cold, and I always have to take out air on the track because they quickly get over 50.

rominl

iTrader: (4)

yes, 600hl should have the same tire pressure. i forgot what 19s should be, but i don't think it's going to be much different at alll. 44 is way too high. i would really do 33psi cold on stock

350Dave

The Lexus tires are transported overinflated, your dealer was negligent in not adjusting the pressures as part of the pre-delivery check.

NEVER BLEED AIR from a warm tire. Always adjust PSI when tire is cold, and only use cold pressure readings to perform future adjustments. IT COULD BE DANGEROUS TO BLEED AIR FROM A WARM TIRE!!!

CEOEngr

Please share why? I see people doing this all the time at the tracks.

zzzzdoc

Yeah. They screwed up that one.

I'm wondering why this is also. I would think pressure is pressure as far as risk. Higher is riskier than lower. Don't see how equal pressures at different temperatures would matter. Unless you're thinking about getting thermal burns from it, which shouldn't remotely be an issue at ~140F, considering the heat capacity of air.

daryll40

When they say to use readings "only when cold"...what does that mean? I generally check my tires every 2 weeks in my garage in the morning before the car is driven. That being said, in the Pittsburgh winter the temps can be as low as zero degrees (garage is about 50 degrees) outside. In the Pittsburgh summer outside temps can be 90 degrees while the garage might be 60 or 65 degrees.

So what is really meant by "check when tires are cold". Is 33 pounds in the "cold" garage the same as if I had parked the "cold" car outside overnight and it was 80 in the morning? Is 33 pounds in the "cold car, but warm garage" the same as if I had parked the car outside last night when it was 10 degrees?

zzzzdoc

The ideal gas law is the equation of state of a hypothetical ideal gas, first stated by Benoît Paul Émile Clapeyron in 1834.

The state of an amount of gas is determined by its pressure, volume, and temperature according to the equation:
PV=nRT
where

P is the absolute pressure,
V is the volume of the vessel,
n is the amount of substance of gas,
R is the ideal gas constant,
T is the absolute temperature.

An ideal gas is defined as one in which all collisions between atoms or molecules are perfectly eleastic and in which there are no intermolecular attractive forces. One can visualize it as a collection of perfectly hard spheres which collide but which otherwise do not interact with each other. In such a gas, all the internal energy is in the form of kinetic energy and any change in internal energy is accompanied by a change in temperature.

An ideal gas can be characterized by three state variables: absolute pressure (P), volume (V), and absolute temperature (T). The relationship between them may be deduced from kinetic theory and is called the Ideal Gas Law.

In practice, I find that the best approach is to take out your calculator, plug in several of the above digits, put the calculator behind your tire, and run over the calculator. If it shatters, you have too much air pressure. If it just gets squished, your pressure is about right.