[jadatis]

Originally Posted by TXPearl

I think we're overcomplicating this. The tire monitoring screen in idrive will tell you what the tire pressure should be based on the current temperature of the tires. It will adjust the recommended pressure as the tire changes temperature. Follow that and you should be OK (assuming you've got it properly spec'd with your tire/wheel combo and max speed parameters).

Can you give me documentation about that recomended pressure changes with temperature (in tire I assume). Then I can use it in other topics to support my idea, that you can let the cold pressure flow with ambient temperature.

And does the recomended in screen also changes when extreme colder ambiënt temperature. For instance 40 or 110 degr F.

And does this then mean that on a cold morning, no low pressure allarm given, as often happens for simpler tmps systems ( I think about 95% in the market)

For some motor tmps they do the other way around.
It gives on screen pressure calculated back to 20 degr C/ 68 degr F.
A system that gives in general less confusion.
Only for those who think further, and wonder why pressure dont rise anymore when driving.

[bubbahead]

22 non-run-flat summer tire. 38 front/44 rear

[Bristle Hound]

I stick with manufacturers recommend tyre pressure for the 22’s on my X5
Seems to work for me

[sharkymcpeterson]

M50, 742’s, conti’s. Running 38 front 40 rear. Car felt bouncier than I liked at high speed with just a couple extra lbs. seems to be a little better at these numbers. I’d be nervous to go lower.

[jad03060]

Load capacity increases up to the maximum listed on the tire as the pressure goes up. That’s one reason why if, say you tow something, the pressure recommendation tends to be higher. If you regularly run lightly loaded, you might be able to get by with slightly less, but since most people don’t adjust it for that occasional heavy load, you are better off using the recommended values, and checking them as the weather changes with the season at least monthly to keep up as the ambient temperature changes.

[Cityman]

41 front/48 rear. Pirelli Pzero performance non-run flats.

[TXPearl]

Originally Posted by jadatis

Can you give me documentation about that recomended pressure changes with temperature (in tire I assume). Then I can use it in other topics to support my idea, that you can let the cold pressure flow with ambient temperature.

And does the recomended in screen also changes when extreme colder ambiënt temperature. For instance 40 or 110 degr F.

And does this then mean that on a cold morning, no low pressure allarm given, as often happens for simpler tmps systems ( I think about 95% in the market)

For some motor tmps they do the other way around.
It gives on screen pressure calculated back to 20 degr C/ 68 degr F.
A system that gives in general less confusion.
Only for those who think further, and wonder why pressure dont rise anymore when driving.

From my online owner's manual under the "Tire Pressure Monitor" section....

Current tire pressure

The current tire pressure is displayed for each tire.

The current tire inflation pressures may change while driving or depending on the outside temperature.

Current tire temperature

The current tire temperatures are displayed depending on the model.

The current tire temperatures may change while driving or due to the outside temperature.

Nominal pressure

The nominal pressure for the tires on the front and rear axles is displayed.

The specified nominal pressures take the influence of driving and outside temperature on the tire temperature into account. The appropriate nominal pressure is always displayed, independent of the weather situation, tire temperatures and travel times.

The displayed nominal pressure may change and may differ from the tire inflation pressure details on the door pillar of the driver's door. The tire inflation pressure can thus be corrected to the value of the displayed target pressures.

The nominal pressure is immediately adjusted if the vehicle load state is changed in the tire settings.

Not sure why the term "Nominal" is used...it corresponds to the recommended tire pressure on my screen.

There may be some minimum recommended pressure level despite extreme low temperatures. Any warning should clear as temps rise while driving, but it may require a reset. [I'm in US/Texas, so extreme lows are very rare]

[mmm50i]

Originally Posted by bubbahead

22 non-run-flat summer tire. 38 front/44 rear

I previously had mine at 39/45 (suggested pressure at MAX LOAD).

But I realized, since my car isn't regularly driven with a max load, I've lowered it to 38/44. Now the ride feels much more comfortable over bumps/manhole covers/rough roads. It's hard to believe 1psi makes a difference, but it does.

[jad03060]

The ideal pressure is what’s on the label WHEN the tires are at the ambient outside temperature BEFORE you have driven, or after they cool back down to ambient. IOW, they should never be below the value on the sticker if you want the stated load capacity, but MIGHT be if they were correct when it was warmer, and now, the weather has cooled significantly. For example, say you set them when they were at 80F in the summer, and now it’s 30F, in the winter, they’d be about 5# low due to the temperature change. Then, as you drive them and they warm, they should show a gradually higher pressure based on them getting hotter. This is a common reason why they might show low when you start out your day, but the warning goes off after you drive…the heat is causing the air to expand and thus the pressure to go up.

The load capacity is based on the CURRENT pressure. This is why it’s important to check them at least monthly as in most places, the ambient temperatures DO change, and that affects the static/nominal pressure in the tires.

When you reset the TPMS systems, you’re telling the computer that this current temperature and pressure is your ‘nominal’ or correct value, and it will adjust the recommended value as the temperature changes.