Tyre pressure: what does this mean?

[Rapido925M]

From an article on GB News (!):

Changes in temperature can cause pressure to contract, meaning air is typically lost at a quicker rate over winter.

MSN

I think it should read: Reductions in temperature causes air to contract, resulting in a reduction in pressure.

I think it should then continue: meaning air is typically lost at a slower rate over winter.

What do you think?
(Other than don't believe anything you read on GB News )

 

[CAB96]

I think they probably AI generate their articles.

I would think they are trying to say that the normal reduction in pressure over time will be exacerbated in cold weather.

 

[Reallyretired]

The low pressure warning on my mini came on with the first frosty day. Tyre pressures are usually stated that they are at 20C and there are tables on the Internet to show the adjustment you should make for other temperatures.
Nothing to do with loss of air, typical of the illiterate journalism we are afflicted with these days can't spell, don't understand grammar and are totally uninterested in factual accuracy.

 

[poppycamper]

The low pressure warning on my mini came on with the first frosty day. Tyre pressures are usually stated that they are at 20C and there are tables on the Internet to show the adjustment you should make for other temperatures.
Nothing to do with loss of air, typical of the illiterate journalism we are afflicted with these days can't spell, don't understand grammar and are totally uninterested in factual accuracy.

Anyone who does not have tyre pressure monitors will be amazed, as I was how much tyre pressure changes with temperature..
Even in summer and you leave with recommended tyre pressure, once travelling that pressure can increase by circa 10 psi..
My tyres are at recommended pressure and in winter temps as we are having now, my tyrepal will alarm,, but very shortly will come back up to operating range.. Yes I could adjust minimun alarm value but it is only in severe cold conditions that they alarm..

 

[Daffy64]

Tyres will naturally lose a very small amount of pressure over time but I think the article means that in colder temperatures the pressures will drop due to the cold - they also increase when the tyres warm up.

A decent TPMS will compensate for temperature but the best way is just to set them cold to the recommended pressure and then check/adjust them every so often.

We did a big project on Truck tyre life some years ago which involved taking pressure readings and adjusting pressures every 6 weeks, basically between January and July we were letting air out and from August to Dec we were putting air in.

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[poppycamper]

Tyres will naturally lose a very small amount of pressure over time

How much.. and over how long..
I do not have to put any air in my tyres both on my moho ( steel rims ) or Mrs Poppycampers car ( alloys ) from one MOT to the next... and before you ask.. Yes .pressures are checked every 2 weeks..

 

[Carpmart]

Tyre pressures should always be measured and set cold, so ambient temperature. My 65psi rear tyres (four on axle) all show nearer to 75psi at running temperature after 30 mins on a Motorway. I prefer 70psi hot, but 60psi is a little too low cold… life’s about compromise!

 

[Whippet93]

I was surprised, having fitted TPMS, the difference between one side, in the sun and the other in the shade on my van, up to 6PSI.

 

[poppycamper]

Tyre pressures should always be measured and set cold, so ambient temperature. My 65psi rear tyres (four on axle) all show nearer to 75psi at running temperature after 30 mins on a Motorway. I prefer 70psi hot, but 60psi is a little too low cold… life’s about compromise!

Exactly my point.. yes summer temps and winter temps are differant.. thus the reason I stated that in winter I was willing to ignore TPMS alarms and wait until temperatures and therefore pressures came back up...

 

[TrudeandDall]

Exactly my point.. yes summer temps and winter temps are differant.. thus the reason I stated that in winter I was willing to ignore TPMS alarms and wait until temperatures and therefore pressures came back up...

Better still. Reset your lower pressure in winter by blowing them up to the correct pressure. Then when things warm up again in spring reduce the pressure by letting the excess air out. TPMS alarms are there for a reason.....

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[poppycamper]

Better still. Reset your lower pressure in winter by blowing them up to the correct pressure. Then when things warm up again in spring reduce the pressure by letting the excess air out. TPMS alarms are there for a reason.....

Yes agreed.. but there is winter and there is winter!!! I was refering to the very occasional times when temperatures drops very low for a day or two.. like now when last 2 nights temp hit minus 9.5C.

 

[The Wino]

Better still. Reset your lower pressure in winter by blowing them up to the correct pressure. Then when things warm up again in spring reduce the pressure by letting the excess air out. TPMS alarms are there for a reason.....

I suppose it depends on the pressure once warmed up when driving. Our friends just got back from Portugal 20 degrees in the daytime 3 at night it would seem a bit over the top to change tyre pressure depending on the time of day! If tyre manufacturers produce tables of pressure against temperature are they saying set it at the same pressure no matter what the temperature or set it at the indicated pressure for the current temperature so as conditions vary it will be within a suitable range I suspect the second!

 

[Rapido925M]

Bear in mind that Gas Laws utilise Absolute (Thermodynamic, Kelvin) temperatures, so 3C to 20C sounds like a lot BUT 276k to 293k doesn't seem so much . In fact, it's a change of about 6% so 60psi should become 64psi IF that is the actual temperature change (probably due to ambient conditions). Once running, the tyre temperature will doubtlessly go higher.

 

[Daffy64]

How much.. and over how long..
I do not have to put any air in my tyres both on my moho ( steel rims ) or Mrs Poppycampers car ( alloys ) from one MOT to the next... and before you ask.. Yes .pressures are checked every 2 weeks..

How long is a piece of string, that would depend on the tyre, application and pressure.

If you are really checking your tyre pressures every 2 weeks and never have to adjust pressures then you need a new gauge as the pressure will fluctuate with ambient temperature - and whilst the tyres will warm with use the ambient temperature as well as position on the vehicle will limit the ultimate temperature and therefore pressure - as already said set your tyre pressures cold and they’ll sort themselves out.

 

[Jon Stewart]

From an article on GB News (!):

Changes in temperature can cause pressure to contract, meaning air is typically lost at a quicker rate over winter.

MSN

I think it should read: Reductions in temperature causes air to contract, resulting in a reduction in pressure.

I think it should then continue: meaning air is typically lost at a slower rate over winter.

What do you think?
(Other than don't believe anything you read on GB News )

Yep. Think you have it right!

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[Barriesimpson]

Exactly my point.. yes summer temps and winter temps are differant.. thus the reason I stated that in winter I was willing to ignore TPMS alarms and wait until temperatures and therefore pressures came back up...

Have you thought about what you have just said? Pressure is measured in psi (in the UK), elsewhere we use bars, it does not matter what the temperature is outside. If the psi needs to be 75, it needs to be 75 in summer and winter. So if the temperature has changed the psi (which it does due to expansion/contraction) then you need to adjust the pressure accordingly, not wait for the summer. If in summer the psi has increased due to temperature rise, then you should again adjust accordingly. This is physics not magic.

 

[dunnah01]

125+ years if blow up tyres and we still can't work out what pressures to use

 

[The Wino]

Have you thought about what you have just said? Pressure is measured in psi (in the UK), elsewhere we use bars, it does not matter what the temperature is outside. If the psi needs to be 75, it needs to be 75 in summer and winter. So if the temperature has changed the psi (which it does due to expansion/contraction) then you need to adjust the pressure accordingly, not wait for the summer. If in summer the psi has increased due to temperature rise, then you should again adjust accordingly. This is physics not magic.

Why then do the tyre manufacturers have charts of pressure against temperature? Surely they would just give one pressure.

 

[Barriesimpson]

Why then do the tyre manufacturers have charts of pressure against temperature? Surely they would just give one pressure.

I have not seen pressure charts against temperatures. The chart is normally on the drivers door frame of the vehicle.

 

[The Wino]

I have not seen pressure charts against temperatures. The chart is normally on the drivers door frame of the vehicle.

Just looked up why they produce them. It's so if you check tyre pressures on a car in a garage you can set an appropriate pressure to allow for the reduction in pressure when you drive outdoors in winter conditions.

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[Daffy64]

Just looked up why they produce them. It's so if you check tyre pressures on a car in a garage you can set an appropriate pressure to allow for the reduction in pressure when you drive outdoors in winter conditions.

I dont think I’ve ever seen one unless it is for a very specific application, can you provide a link please?

 

[The Wino]

I dont think I’ve ever seen one unless it is for a very specific application, can you provide a link please?

From a previous fun post

And another one

 

[Daffy64]

From a previous fun post

View attachment 998932
And another one

View attachment 998934

Thanks for that, I think that if it relates to tyres and produced by the manufacturer then it’s more R&D or competition than designed for real world applications where the message is always set them cold (i.e. ambient temperature)

 

[The Wino]

Thanks for that, I think that if it relates to tyres and produced by the manufacturer then it’s more R&D or competition than designed for real world applications where the message is always set them cold (i.e. ambient temperature)

I think the reason they produce the tables from what ive seen is that if you have a car in a garage and are going out in winter you are supposed to increase the pressure in anticipation of it reducing outside.

 

[Brains]

It's GB "news"
Which means if they said "good morning" I'd be checking my watch to make sure it was before midday.

I'd actually bother to look at the issue until it came from an actual recognised news source.

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[Daffy64]

I think the reason they produce the tables from what ive seen is that if you have a car in a garage and are going out in winter you are supposed to increase the pressure in anticipation of it reducing outside.

Thanks for sharing that, I’ve just done a search on the image and there are variations of the image, the general theme seems to be motorsports related, so I guess the garage would relate to the pit garage where I could see some use as tyre temps are very high so the pressures are critical.

 

[Mike800966]

Thats why they pre-warm the tyres with electric covers
Boyles Law: Pressure, Volume and Temperature. If you change one the others change to remain a constant value.
On a hot day on a long motorway drive, like in Spain, you can see the difference between the sunny and shaded sides.
Mike

 

[Rapido925M]

Being pedantic, Boyle's Law only applies to P & V (temperature needs to be constant).
General Gas Law: P & V / T is constant

 

[Jon Stewart]

Thats why they pre-warm the tyres with electric covers
Boyles Law: Pressure, Volume and Temperature. If you change one the others change to remain a constant value.
On a hot day on a long motorway drive, like in Spain, you can see the difference between the sunny and shaded sides.
Mike

Boyle's law relates pressure and volume.
Charles' law relates volume and temperature.

The universal gas law relates all three!

I prefer Coleslaw, though.

 

[Mike800966]

Quite amazing to look into the stories of all those people who developed these rules.
Not forgetting ohms, volts and amperes, Oersted, Curies.
Us mortals know so little, we have so much yet to learn.
Mike

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