jadatis

The influence of water is exagerated by the Nitrogen lobby.
In the extreme situation, I mentioned in former post, so driving with yust enaugh pressure for load and speed in ambiënt temperature of 40 degr F / 104 degr F, temp in tire can rise with no external factors to 75 degr C/ 167 degr F.
Then 30 psi cold filled at 68 degr F rises to 38.4 psi if completely dry gascompound in tire, and 43.6 psi if enaugh water in tire, even if a gallon liquid water. So yes, 5.4 psi higher.
But because this higher pressure gives lesser deflection, so heatproduction, in practice the temperature in tire rises a little less, so lower pressure rising, I estimate to 41 psi wet wich is a wet temperature in tire of 155 degr F.

And because liquid water has gone over to gas, more gas in tire, wich cools down better the tire material, wich is max allowed 120 degrC/ 248 degr F.

30 psi filled at 68 degr F on a empty tire, and 100% humidity, gives that little water in tire, that at 104 degr F all the water is gas and only 0.7 psi more by water, and from that temp water is yust another gas in the gascompound so dry calculation counts, and gives at 167 degr F 39.2 psi. This against the 38.4 psi absolutely dry is only 0.8 psi more.

jadatis

But this higher pressure gives lesser deflection so lesser comfort.
So mayby cold pressure can be lower for your situation.
To determine a safe lower pressure, I can make you a cold pressure /axleloadcapacity list with build in maximum reserve, at wich comfort and gripp is still acceptable.
For that I give 90% of calculated axleloadcapacity for the cold pressure for max 160kmph/99mph.

Then you " ONLY" have to determine the axleloads 99% acurate, and search them back in my list.
The most tricky part and your responcibility.
Then temp in tire and of tire material will get a bit higher, but not to hot still.

Need next to make the list.
1. Maximum load or loadindex
2.standard load or XL/reinforced / extraload to determine the reference-pressure
3 speedcode, less important, shall be Q or above, for wich maxload is given for 160kmph/99mph.

Also give your maximum speed used, and wont go over for even a minute.
And if you want list in bar or psi, kg or lbs.
GAWR's and GVWR, empty weight and way you load it with persons and load would be handy to dangerously estimate the axleloads in use.
​

Brent4880

I took my 09 out for a drive a couple days ago when the temperature got up to mid 50s F. Starting out, I got a low pressure message for two tires. I have 7 month old Michelin PS AS4 ZPs. I don’t think I exceeded 60mph. After about 5 miles, one tire’s lp message stopped and by around 9 miles, the second lp message disappeared. Tires get hotter when driving and the tire pressure increases.

It’s cool some of you guys can accurately calculate tire pressure as its temperature changes. I imagine that information is very helpful when doing track days and racing. For some of us more casual drivers, being aware that cooler seasonal air temperatures lower tire pressure is probably enough. Tire type, use, and how much the pressure is low should influence how this issue is dealt with. This is the third winter I’ve owned my Corvette and with the ZPs (zero pressure) and the planned casual drive last week, I chose not to check and add air pre-drive. I think it went fine as all 4 tires did reach enough pressure to satisfy the sensors in less than 10 miles.

jadatis

Protesting of the tmps system can be anoing, but stays a secundary problem.

But to my discussable conclusions in time, at lower ambiënt temperature, you can do with lower pressure, when only for savety of tires, so they dont overheat.
More heatproduction by more deflection the lower cold pressure gives, but also more cooling down, by the more temperature differences between tire-material, and in and outside tire gascompound.

When hot outside the other way around, and then certainly dont lower the pressure.

But when cold outside, you may highen up for roadhandling and fuelsaving, but to prefent overheating, main goal, not needed.

General is written to fill cold 30 psi, if that is what determined needed, at ambiënt temperature, be it 20 or 110 degr F.

My idea, to let it flow with temperature change, is easyer, and will be proven right in about 20 years.

RIMEX and B-alert, both for mining tires, underline my idea.
​​​​​​RIMEX uses 20 degrC/ 68 degr F as index temperature, and B-alert uses in example 15 degr C/ 59 degr F as temperature to calculate back pressure to.