I inflated my summer tires this spring to about 250 kPa (a bit more than the default 240 kPa). Temperatures at that time were about 18°C / 64°F.
We now have very high air temperatures of up to 36°C / 97°F. Tire pressure monitoring now shows values of up to 286 kPa on all tires during driving.

Is this pressure level to be expected? Is it within the tires' limits? Or should I deflate them a bit?

 

The tire limit is printed on the tire sidewall; usually around 32 PSI.

Inflating with nitrogen moderates that by quite a bit.

 

Check your tire pressure cold , adjust the tire pressure accordingly.
What is 240 kpa in January will be much higher in June.
I check tire pressure every week, and adjust to the pressure on the sticker on drivers door jamb , for mine 32psi.
my tires say 35 lbs max

 

Only go by cold tire pressures when doing comparisons. Never compare those with the driving ,heated up tire temps.

I can start out with 32 psi.on a summer day. Hit the highway, and all tires will heat up to 35 or 36 psi after an hour or so on the road.
In fact, the other day I started with all at 30 psi. Did a short 6-7 mile run to the store. All tires were up to 32.
(No, I don't have nitrogen in mine)

 

Yes you do, 78%.

 

But mine's "watered down" with 21% oxygen and 1% other inert gases...AKA- normal air.
OK. Enough of Science 101. Now back to our regular scheduled program.

 

If your tires are hot use a hose with cold water.

 

Odd factoid; the tires will heat up more and over inflate if you start out with low pressure cold. The sidewalls flex more and cause heat build up. Try it before naysaying.

 

Don't you think the compound of the rubber plus road temperatures are a factor ?
Have you ever done drag racing or circle track and measured track temps or surface contact of a tire to "try" to calculate tire pressure ?

 

The road temp has nothing to do with sidewall flex. The many layers of material rubbing together warms them up quite a bit.

One of the many reasons for maintaining the proper pressure. Case in point: 1998 Exploder with original tires. Firestone said the reason for failure was that Ford recommended 26 PSI and that led to tires over heating and exploding. https://en.wikipedia.org/wiki/Firest...re_controversy

[QUOTE][A tire's operating temperature will increase with higher vehicle load, speed, air temperature and with lower tire inflation pressure. [color=Green]The combination of inflation pressure, speed, and vehicle load could increase the tire temperature as much as 50 degrees C above the ambient air temperature.[39] Higher operating temperatures will increase the rate of oxidative aging.[39] Tires that were used in southern climates were less ductile and stiffer than tires that operated in northern climates.[39] Tires in warmer climates also showed higher levels of cure and had somewhat lower peel strength.[39] The role of air temperature would explain why geographic regions with higher air temperatures had the highest tire failure rates. These results held up even for tires that had zero percent tread wear.[39]

Higher vehicle loads increased belt crack growth rates. Of the four factors involved in the growth of cracks in the tires, vehicle load was the single most important factor. [39]

The Explorer weighs more than the Ford Ranger and has a higher Gross Vehicle Weight Rating (GVWR) while also having a lower recommended tire pressure.[2] This difference in weight and tire pressure explains why Ford Explorers had far more tire failures than Ford Rangers even though they used the same tire models. Despite these differences, investigators were concerned that Ford Rangers would also see an increase in tire failures if those tires weren't recalled.[2]

/QUOTE]

At least part of the problem was heat buildup due to under inflation from the factory setting. Then normal vehicle load on top of under inflation.

Like I said: "try it before naysaying".