Recommended tire pressure too high

[SammichLover]

interesting, but I suppose it makes sense. Your car is about 400 pounds heavier than mine, so I can see more pressure being helpful.

Mine actually bled down to 32–33 before I aired them up yesterday, and I noticed no negative handling characteristics at all. Definitely less jittery than when they were at 45.

You have an SR+ or a LEMR? Good point, that could indeed be a factor.

It’ll also depend on how hard you turn-in, too. I normally do so near the maximum allowed by law, and since there isn’t law short of “don’t hit the ditch/curb/bystanders” ...

If you don’t turn hard you might not notice until that time you need it. But in the meantime you sidewalls will be heating with the extra flex (where a lot of the RR energy goes).

At 45 PSI the “jittery” is just the road coming through. They respond lightning quick, too, but the are so high pointed in the middle of the tire traction is compromised as is wear (later creates clear, easy to spot sign of “overpressure”).

 

[Jandieg]

On 19" I use 40 on front and 38 rear. I think is a good compromise for comfort. With stock 42 the ride was so stiff (since I have lowering H&R kit)

For long straight forward trips I would put 42 all.

I also fill tires with nitrogen so heat will not bloat them too much.

 

[Watts_Up]

I also fill tires with nitrogen so heat will not bloat them too much.

Ambient air has 80% of Nitrogen, cannot really notice a difference of pressure between air and Nitrogene when the temperature increase?

 

[Jandieg]

Ambient air has 80% of Nitrogen, cannot really notice a difference of pressure between air and Nitrogene when the temperature increase?

In Dubai it can make some difference

What I get is +1 PSI between night/day (eg 30° to 45°). With air it would be +2PSI.

Little difference of 1PSI

 

[vickh]

In Dubai it can make some difference

What I get is +1 PSI between night/day (eg 30° to 45°). With air it would be +2PSI.

Little difference of 1PSI

would be same here in Phoenix AZ i think. esp since i usually get air topped in middle of day. My Pirelli' Z elects seem to slow leak more than OEM Michelins too

 

[texas_star_TM3]

would be same here in Phoenix AZ i think. esp since i usually get air topped in middle of day. My Pirelli' Z elects seem to slow leak more than OEM Michelins too

i noticed the same. love my P Zero elects.... but they do drop (all tires, not just one) around 1 psi every 2 weeks or so (same temperature and time of measuring)

 

[DD27]

i noticed the same. love my P Zero elects.... but they do drop (all tires, not just one) around 1 psi every 2 weeks or so (same temperature and time of measuring)

Also noticed the same, thought it was just me!

 

[rpiotro]

The OEM Michelins on my M3 SR+ have no leakage at all. After 13 months. Zero. In my 55 years of driving this is a first. I wonder how they do it?

 

[Perscitus]

YMMV, but with stock suspension and a good alignment, even (front/back, side to side and groove to groove) tire wear... MPP recommends cranking the tire pressure up to 46-48psi on stock or stock-like spec 18s/19 tires.

This results in at-highway cruise steady-state warmed up tire pressure at around 50-52psi. And drops back down to 46-48psi cold tire pressure.
Drop that a tad (say 2-4psi) for added wet/snow traction and or comfort.

Some even opt for approaching or reaching the max cold tire pressure spec on the sidewall of a given tire (there were threads on here to that effect).
No or limited ill effects from doing so vs say having a badly toe'd-in/-out suspension geometry.

I find that the optimal cold tire pressure with these cars is (as many other things automotive and in life) ultimately a personal preference/choice.

A compromise with pros and cons on either end of the spectrum.

Lots of variables from tire specs used climate/ambient conditions, road surface, suspension setup, perception of and desired comfort level, car usage pattern, etc.

 

[vickh]

The OEM Michelins on my M3 SR+ have no leakage at all. After 13 months. Zero. In my 55 years of driving this is a first. I wonder how they do it?

yes very unusual. Spoilt and I might go back to the Primacy

 

[Gasaraki]

Ambient air has 80% of Nitrogen, cannot really notice a difference of pressure between air and Nitrogene when the temperature increase?

It actually makes a bigger difference than I thought. In NY, the daily temperature can vary by 30+ degrees a day. If it's been hot for a few days and I have my tires inflated to 42 (idle temp pressure) and the next day it could be in the 60s. I've seen the pressure then drop to 37 or so and then the tire pressure light turns on in the morning but turns off after a short drive.

 

[Tronguy]

It actually makes a bigger difference than I thought. In NY, the daily temperature can vary by 30+ degrees a day. If it's been hot for a few days and I have my tires inflated to 42 (idle temp pressure) and the next day it could be in the 60s. I've seen the pressure then drop to 37 or so and then the tire pressure light turns on in the morning but turns off after a short drive.

Um.

Basic chemistry: The Ideal Gas Equation is Pressure * Volume = n * R * T, where:

n is the number of moles of the gas.
R is a fudge factor.
T is the temperature in Kelvin.

The "R" value depends upon what units one is using: Pascals of pressure, volume in liters, and so on. R is pretty much fixed until one gets crazy, where, "crazy" means any of the following:
1. One is playing around where the gases are liquefying, either due to extreme pressure or ridiculous cold.
2. The gas is ionizing, usually due to ridiculously high temperatures.

Neither of the above is true at any temperature we tend to run cars around in.

Generally, if one solves for Pressure, one gets this: P = (n*R)*T/V.

Hokay. Fill the tire up with Nitrogen, standard air, or, I dunno, Helium. Or Krypton. (That is a gas, not an anti-Superman thing.) As it happens, for any gas, one mole of that gas occupies 22.4 l at 0 C. So, one might have different amounts of mass of air in the tire, but the number of molecules will be the same.

So, one fills up a tire when it's, say, 35C out there, to a set pressure above ambient, say, 52 psi. Volume is fixed. "n" is fixed. "R" is fixed. T is not fixed and can go up and down. And, sure and begorrah, the pressure will go up and down with the temperature. So:

delta-P = (n*R/V)(delta-T).

Period. I strongly suspect that changes seen by a single PSI or so is simply measurement error.

Now, if one wants to argue that dry Nitrogen doesn't have any water dissolved in it, which normal air at some compressor will, then, sure. I suppose a bit of water could cause corrosion. Or if one filled up one's tires on a really humid day when it's 45C out, then drove straight to somewhere where it was below freezing (and didn't back-fill more air because, natch, the tire pressure would have dropped), there might be some condensation and/or ice forming in there. Betcha airliners have issues like that, given that flying around at 40,000 feet gets one well below freezing. (And probably explains why their tires get filled with Nitrogen.) And.. I made a joke about the Helium, but Helium (or Hydrogen) are teensy little molecules that leak through things relatively easily.

I just looked it up: Nitrogen (N2) molecules are 3.15 A in diameter, Oxygen (O2) is 2.98 A; so I guess Nitrogen will leak out slightly slower. Krypton has a diameter of 4 A or so, so would be even better, but more expense.

I think this whole business with Nitrogen is the same thing as gold-plated wires used by the maniac audiophiles: Doesn't do anything for anybody, but it sure is more expensive.

 

[brkaus]

I just looked it up: Nitrogen (N2) molecules are 3.15 A in diameter, Oxygen (O2) is 2.98 A; so I guess Nitrogen will leak out slightly slower. Krypton has a diameter of 4 A or so, so would be even better, but more expense.

So, over time the oxygen will be more likely to leak out and the % of nitrogen will slowly rise as the tire repeats the leak/refill cycle.

 

[Gasaraki]

Um.

Basic chemistry: The Ideal Gas Equation is Pressure * Volume = n * R * T, where:

n is the number of moles of the gas.
R is a fudge factor.
T is the temperature in Kelvin.

The "R" value depends upon what units one is using: Pascals of pressure, volume in liters, and so on. R is pretty much fixed until one gets crazy, where, "crazy" means any of the following:
1. One is playing around where the gases are liquefying, either due to extreme pressure or ridiculous cold.
2. The gas is ionizing, usually due to ridiculously high temperatures.

Neither of the above is true at any temperature we tend to run cars around in.

Generally, if one solves for Pressure, one gets this: P = (n*R)*T/V.

Hokay. Fill the tire up with Nitrogen, standard air, or, I dunno, Helium. Or Krypton. (That is a gas, not an anti-Superman thing.) As it happens, for any gas, one mole of that gas occupies 22.4 l at 0 C. So, one might have different amounts of mass of air in the tire, but the number of molecules will be the same.

So, one fills up a tire when it's, say, 35C out there, to a set pressure above ambient, say, 52 psi. Volume is fixed. "n" is fixed. "R" is fixed. T is not fixed and can go up and down. And, sure and begorrah, the pressure will go up and down with the temperature. So:

delta-P = (n*R/V)(delta-T).

Period. I strongly suspect that changes seen by a single PSI or so is simply measurement error.

Now, if one wants to argue that dry Nitrogen doesn't have any water dissolved in it, which normal air at some compressor will, then, sure. I suppose a bit of water could cause corrosion. Or if one filled up one's tires on a really humid day when it's 45C out, then drove straight to somewhere where it was below freezing (and didn't back-fill more air because, natch, the tire pressure would have dropped), there might be some condensation and/or ice forming in there. Betcha airliners have issues like that, given that flying around at 40,000 feet gets one well below freezing. (And probably explains why their tires get filled with Nitrogen.) And.. I made a joke about the Helium, but Helium (or Hydrogen) are teensy little molecules that leak through things relatively easily.

I just looked it up: Nitrogen (N2) molecules are 3.15 A in diameter, Oxygen (O2) is 2.98 A; so I guess Nitrogen will leak out slightly slower. Krypton has a diameter of 4 A or so, so would be even better, but more expense.

I think this whole business with Nitrogen is the same thing as gold-plated wires used by the maniac audiophiles: Doesn't do anything for anybody, but it sure is more expensive.

The long and short of it is that nitrogen filled tires DO migrate temperature expansion etc but not needed for normal users. But saying that there is no difference is a lie because race cars use it.

Nitrogen in tires | Continental Tires

Did you know you can inflate tires with nitrogen instead of with air? Learn about the pros and cons of having nitrogen-filled tires on your wheels.

www.continental-tires.com

 

[vickh]

The long and short of it is that nitrogen filled tires DO migrate temperature expansion etc but not needed for normal users. But saying that there is no difference is a lie because race cars use it.

Nitrogen in tires | Continental Tires

Did you know you can inflate tires with nitrogen instead of with air? Learn about the pros and cons of having nitrogen-filled tires on your wheels.

www.continental-tires.com

+1
i wish more national places other than Costco did it.

 

[rjpjnk]

Um.

Basic chemistry: The Ideal Gas Equation is Pressure * Volume = n * R * T, where:

n is the number of moles of the gas.
R is a fudge factor.
T is the temperature in Kelvin.

The "R" value depends upon what units one is using: Pascals of pressure, volume in liters, and so on. R is pretty much fixed until one gets crazy, where, "crazy" means any of the following:
1. One is playing around where the gases are liquefying, either due to extreme pressure or ridiculous cold.
2. The gas is ionizing, usually due to ridiculously high temperatures.

Neither of the above is true at any temperature we tend to run cars around in.

Generally, if one solves for Pressure, one gets this: P = (n*R)*T/V.

Hokay. Fill the tire up with Nitrogen, standard air, or, I dunno, Helium. Or Krypton. (That is a gas, not an anti-Superman thing.) As it happens, for any gas, one mole of that gas occupies 22.4 l at 0 C. So, one might have different amounts of mass of air in the tire, but the number of molecules will be the same.

So, one fills up a tire when it's, say, 35C out there, to a set pressure above ambient, say, 52 psi. Volume is fixed. "n" is fixed. "R" is fixed. T is not fixed and can go up and down. And, sure and begorrah, the pressure will go up and down with the temperature. So:

delta-P = (n*R/V)(delta-T).

Period. I strongly suspect that changes seen by a single PSI or so is simply measurement error.

Now, if one wants to argue that dry Nitrogen doesn't have any water dissolved in it, which normal air at some compressor will, then, sure. I suppose a bit of water could cause corrosion. Or if one filled up one's tires on a really humid day when it's 45C out, then drove straight to somewhere where it was below freezing (and didn't back-fill more air because, natch, the tire pressure would have dropped), there might be some condensation and/or ice forming in there. Betcha airliners have issues like that, given that flying around at 40,000 feet gets one well below freezing. (And probably explains why their tires get filled with Nitrogen.) And.. I made a joke about the Helium, but Helium (or Hydrogen) are teensy little molecules that leak through things relatively easily.

I just looked it up: Nitrogen (N2) molecules are 3.15 A in diameter, Oxygen (O2) is 2.98 A; so I guess Nitrogen will leak out slightly slower. Krypton has a diameter of 4 A or so, so would be even better, but more expense.

I think this whole business with Nitrogen is the same thing as gold-plated wires used by the maniac audiophiles: Doesn't do anything for anybody, but it sure is more expensive.

Yep. PV=nRT for any gas. Nitrogen will vary just as much with temperature as regular air. Main benefit of N is it is dry. No moisture. Water is not compressible and not good in tires. And you get a green valve cap

 

[vickh]

Yep. PV=nRT for any gas. Nitrogen will vary just as much with temperature as regular air. Main benefit of N is it is dry. No moisture. Water is not compressible and not good in tires. And you get a green valve cap

theres my problem, a red TSLA valve cap

 

[KenC]

I just like that my tire place gives me 78% Nitrogen for free any time I want.

 

[Tronguy]

So, over time the oxygen will be more likely to leak out and the % of nitrogen will slowly rise as the tire repeats the leak/refill cycle.

Except that.. We're talking about (a) the seals from the tire to the wheel rim, (b) the bits of rubber in the valve, and (c) whatever-the-heck-it-is that leaks through bulk rubber.

I've heard stories where H2 molecules (diameter: 2.7 A.. But an individual hydrogen atom has a diameter of 1A, and then one has to look at what one is talking about. A hydrogen atom is one proton plus an electron, more or less, and, well, a proton by its lonesome is tiny. I've heard stories where protons (i.e., hydrogen atoms, minus their electron) work their way through the interstices of solid steel and come out the other side. (Universal Solvent Corporation, Container Division. How may I help you?) Nitrogen, Oxygen, and Krypton have multiple layers of electrons (2 in the inner shell, various in the outer shells) which makes them less likely to Do That Kind of Thing.

So, frankly: I think you'd have to wait years before the 80%/20% split of N2/O2 would be noticeable.

The bit about there not being any water in the N2 being pumped into a tire is probably more important. But I found a AAA web site a few days back: They stated that most commercial compressor systems in auto shops come with a drier filter in the inlet air, because mechanics don't like seeing their tools and hardware rust any more than the next guy. If they're doing that.. Then why are we going crazy about N2?

Frankly, it's back to audiophiles and gold-plated wires. At audio frequencies. Or, for that matter, gold-plated HDMI cables. Makes no difference, costs more, and fools the unwary.

 

[SMAlset]

Back in the old days of Model 3 (like my 2018 Jan LR RWD) 45 was the value, some thought the ride was too harsh so apparently it was changed (among other things). My 2018 August car shows 42 as the spec.

My car running OEM 19" wheels / tires is set to cold pressure of 45. No unusual wear but I also did have the alignment fixed a couple months back due to an ever so slight drift to the left.

I should note I always tend to run my tire pressures a little bit higher, I'm more interested in whatever small range increase I might get and the slightly firmer more responsive ride that comes with mildly higher pressures... in this car, I can feel when they are too inflated, the car suddenly becomes much rougher riding and handling sharpness drops.

YMMV

View attachment 399491

For those that noticed, yes this stealth performance car came with 18 but I swapped them out for OEM 19s

And my 2018 Model 3AWD LR with 19s also indicated 42psi on door jam.

I had car in for service today for glass replacement and they did their tire check. I periodically check the psi and inflate as needed. Was told today my rear tires should be replaced. Fronts were 5/32s but rear driver was 4/32 and rear passenger 3/32. Pressure was fine.