Correct tyre pressure for low temperatures?

[Marcusthehat]

The warning light came on on Tue morning past, but the tyres looked 100% so I ignored the warning, the light then went out, this repeated again on Thursday. Tyres still looked 100%.

Anyway I checked the book and pumped them to 33psi this frosty morning, except they were all consistently reading just over 20psi(and my gauge may well be faulty?, so I will check it or buy another)

BUT!

Disregarding any erroneous TPG readings, for now, this begs the question of the effect of ambient temperature on tyre pressures, so how does one correct for inflation at say 0 deg C, since the handbook did not appear to take temperature into account, leastwise that I remember seeing. 

(Intersnot just told  me 1psi per 10 deg)

cheers

marcus

 

[dannyboy413]

My tyre pressure warning light came on Thursday morning. The outside temperature wa -2°C. Like you, everything looked alright. I dropped my wife at work and half way home I noticed the light had gone out. I checked the pressures later in the day and the front n/s was 1 psi less than the others. I put a bit of air in and no problem since - and it has been colder both Friday and today.

[Roy124]

There you go Marcus.  In the ISA model, the standard sea level pressure/temperature is 29.92 in. (1,013.25 mb) and 59°F (15°C).

 

!Removed! -Lussac's Law

The name of the person removed is a word similar to happy, rhymes with Day. 

When the temperature of a sample of gas in a rigid container is increased, the pressure of the gas increases as well.

Though a car tyre is not a rigid container. 

Using your figure. Had you filled your tyre when hot after a run it might be 30-40 degrees.  It would loose 2.5 to 3 psi at ISA and another 1.5 psi at freezing. 

I believe Frosty said the TPMS will show low pressure when it drops by 20%.  For instance with 30psi you might get a warning at 24psi.  Your properly inflated hot tyre has already lost 4psi.  It you have a slightly under inflated tyre it can soon put up a warning.  The warning goes away as the tyre get hot 

[TonyHSD]

Best practice for correct tyre pressures is to measure them before driving off  and remain close to the numbers shown on the door label. For more precise check and adjust using bar instead of psi. To add for the cold temperatures and harder rubber you can do just a bit lower than the recommended for example if 2.3bar you can do 2.27 and in the hot days can do 2.34 bar still within the specs and close to 2.3 bar. Using a good quality tyre gauge is also important. https://www.ebay.co.uk/itm/285046923458?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=2fWrzZ2QSjK&sssrc=2349624&ssuid=p34UK1z2T4m&var=&widget_ver=artemis&media=COPY

[philip42h]

37 minutes ago, Marcusthehat said:

so how does one correct for inflation at say 0 deg C, since the handbook did not appear to take temperature into account

We all check and adjust our tyre pressures at least once a week ... surely ... don't we? 🙂

Provided that we regularly check and adjust the tyre pressures we will never deviate too far from the 'required' 33 psi - the tyres should be at 33 psi regardless of temperature.

But there is some evidence that the TPMS pressure setting may be set rather too high from the factory / at Burnaston or wherever. So it may be worth accurately setting your tyres to 33 psi all round and then resetting the TPMS warning level.

[ernieb]

My front offside is currently showing a problem but the readings are the same on each corner. Just leaving it where it is, I do find that once warmed up, car running, the tyre pressure will go up.

[Marcusthehat]

2 minutes ago, ernieb said:

My front offside is currently showing a problem but the readings are the same on each corner. Just leaving it where it is, I do find that once warmed up, car running, the tyre pressure will go up.

That cuts to the crux, if say one set the pressures on a frosty morning, then hammered down a M-Way, temperatures and pressures must rise, surely, but I suppose no different to a cool summers morning and then hammering down an M-Way mid afternoon with ambient temperatures in the 30's.

All in all a bit of a movable feast, so I am thinking that;

**perhaps the TPMS needs some  temperature compensation software? ,

since apparently it does not, per my and other supporting observations above, if a cold morning causes it to trigger a warning.

**Odd that the engineers would not have anticipated this factor?

 

 

[APS]

What Ernie said. The TPMs can be a nuisance. "Back in the days" I regularly drove in very cold weather (temperatures down to below -30º C) and the tyre pressures really were the least of my worries. Tyres warm up a little as you drive. In short, I never adjusted pressures for those conditions.  It's good to be warned about pressure changes, but I'd also want to be able to silence the system once I've done a quick visual and manual check. 

[Roy124]

10 hours ago, philip42h said:

 🙂But there is some evidence that the TPMS pressure setting may be set rather too high from the factory / at Burnaston or wherever. So it may be worth accurately setting your tyres to 33 psi all round and then resetting the TPMS warning level.

As I documented previously, my Yaris Cross made in France and shipped through Derby, had 2.7 bar on all 4 tyres. The correct pressure should be 2.1F 2.0R.

The lesson is don't assume, CHECK 

[Roy124]

Taking Marcus premise:

Assume the tyre pressures are set to the recommended pressure at ambient temperature before the journey.  Will the kinetic temperature increase on the motorway be the same amount winter or summer?

An associated thing, checking the pressures when cold, if the car has been subjected to solar radiation on one side and shade on the other, we might get a significant imbalance if we set all tyres to the same value. 

Oops 

 

[Corollanutter]

I had this same issue a couple of months ago when it wasn’t as cold as it is now. Fixed it by checking and balancing all pressures at cold - and then resetting the TPMS via the dashboard. Quite possibly the TPMS was previously set with slightly skewed tyre pressures. Hasn’t done it again since - even with the current temperatures. I do believe that the TPMS sensors also measure temperature, so I’m not sure if the system works out a compensation for hot and cold. 

[ColinB]

11 hours ago, Roy124 said:

As I documented previously, my Yaris Cross made in France and shipped through Derby, had 2.7 bar on all 4 tyres. The correct pressure should be 2.1F 2.0R.

The lesson is don't assume, CHECK 

My RAV4 Excel turned up with the tyres inflated to 44psi in old money.....

[TonyHSD]

In the freezing cold weather best to keep tyre pressure slightly below the max allowed to make extra contact area and increase rolling resistance and grip especially if you are driving on stock summer tyres. If your recommendations is 2.3 bar set these at 8C° but if you check them at -4C° you will be better off setting them at 2.25 bar . Safer , quieter and more comfortable drive, plus when weather goes back to more normal temp they will be at exact 2.3bar no need to adjust , just a quick check to confirm👌

[FROSTYBALLS]

TPMS will show an error when a loss of around 20-25% is detected. Colder weather can lead to lower tyre pressures, and, for example, during winter errors may show until the tyre has warmed up sufficiently.

Aside from adjusting tyre pressures in colder weather, one way to avoid these false warnings, is to increase the tyre pressures by a couple of psi or so above the recommended levels, reset the TPMS, and lower the pressures back to the recommended. 

For example if the recommended pressure is 35psi, the TPMS may show a warning if it detects a pressure 'loss' of approx 7-8.75psi. A  pressure of 38psi may show a warning if it detects a pressure 'loss' of 7.6-9.5psi - which may be enough to avoid similar false warnings during outside weather temperature fluctuations.

At the end of the day the system isn't designed to be a management tool for tyre pressures, but a warning of a possible substantial pressure loss.

[Stivino]

You should inflate your tyres in cold weather according to tyre manufacturers.

[Hayzee]

My TPMS was set at 33psi and showed an error message at 29psi

[Roy124]

13 hours ago, Stivino said:

You should inflate your tyres in cold weather according to tyre manufacturers.

This is the advice from Goodyear (as on my Yaris Cross) 

Even in ideal conditions they lose about 0.069 bar or 1 pound per square inch (psi) per month – and that’s a figure that rises with the temperature.

So check your tyre pressure at least once a month, and while you’re at it have a good look at your treads.

They do not recommend a departure from/

The recommended pressure for your tyres can be found in your vehicle handbook

At least with the Cross Smart Connect that is an easy task and a routine to adopt 

 

[Stivino]

5 minutes ago, Roy124 said:

This is the advice from Goodyear (as on my Yaris Cross) 

Even in ideal conditions they lose about 0.069 bar or 1 pound per square inch (psi) per month – and that’s a figure that rises with the temperature.

So check your tyre pressure at least once a month, and while you’re at it have a good look at your treads.

They do not recommend a departure from/

The recommended pressure for your tyres can be found in your vehicle handbook

At least with the Cross Smart Connect that is an easy task and a routine to adopt 

 

I wouldn't deviate from the recommended pressures either.  Without quoting it, my post was in reply to a post suggesting that pressures should be decreased during cold weather.

[TonyHSD]

Not meant that at all, to reduce tyre pressure when cold, but only take into account when topping up. 

Pressure can be adjusted to accommodate the lower temperature when checking and it’s freezing cold like was yesterday -4C° , if you set the pressure exact as manufacturers recommended the next week they will be way over the recommended numbers as it will be +8 C° Also the most drivers in uk drive on summer tyres which become hard as rock in anything below 10C° and keeping them at ,ax recommended pressure will make your car even dangerous to drive. 

Not necessary to agree or follow my tips. They will be helpful to others for sure. 👌

Important to note : 

- Cold tyre pressures check means one thing, check before you drive off and not check when it’s cold outside. 👍

And yes I do check my tyres at least once a week, sometimes more. I also do measure how they heats up and how they change pressures as a result. , I know what I am talking about., and I also know I am not wrong. 

[Stivino]

I think I will stick to the advice given by both the car manufacturer and the companies who make the tyres.

 

[JARC1]

On 12/10/2022 at 9:58 PM, TonyHSD said:

Best practice for correct tyre pressures is to measure them before driving off  and remain close to the numbers shown on the door label. For more precise check and adjust using bar instead of psi. To add for the cold temperatures and harder rubber you can do just a bit lower than the recommended for example if 2.3bar you can do 2.27 and in the hot days can do 2.34 bar still within the specs and close to 2.3 bar. Using a good quality tyre gauge is also important. https://www.ebay.co.uk/itm/285046923458?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=2fWrzZ2QSjK&sssrc=2349624&ssuid=p34UK1z2T4m&var=&widget_ver=artemis&media=COPY

"For more precise check and adjust using bar instead of psi. "

Why is bar more precise than psi ?

Regards, John 

[TonyHSD]

On 12/12/2022 at 1:01 PM, JARC1 said:

"For more precise check and adjust using bar instead of psi. "

Why is bar more precise than psi ?

Regards, John 

Hi John, 

you can do in either way with bar or psi however in bars you can increase or decrease by 0.01 and most digital gauges can detect and display the numbers where in psi the steps goes by 0.5 psi on most gauges I had used. Example 2.3 bar so you are good anywhere from 2.25 2.26 2.27 up to 2.35 bar where in psi likely to be measured either 33 psi or  32psi or 34psi , and in more accurate ones up to 33.5psi or down to 32.5psi. These are small numbers and likely not been noted on most cars by most drivers but in my Auris with not so finely tuned suspension  any small number matters and can be felt through the car., as either hard and unpleasant or as smooth and soft ride. ,. The sweet spot is exactly in between. 🛞👌

[Talshia]

The Tyre Pressure warning Indicator symbol came on on my car three days ago, it was minus 2 outside.

I checked the pressures, they were all 29 psi, I inflated them all to 33 psi and after driving or 200 metres the alarm extinguished, and has not activated again.

Question ? Is there any way of knowing which tyre has set off the alarm ?

Keep safe

Paul

 

[Strangely Brown]

43 minutes ago, Talshia said:

Question ? Is there any way of knowing which tyre has set off the alarm ?

I don't wish to appear flippant but have you tried measuring all four and looking for the low one?

If all four are the same then it is likely just low temperature and the air inside the tyre contracting.

AFAIK, the TPMS does not show individual pressures, which would be nice.

[philip42h]

35 minutes ago, Strangely Brown said:

AFAIK, the TPMS does not show individual pressures, which would be nice.

Within the ECU thingy it will know which TPMS valve triggered the alarm ... but it doesn't know which TPMS valve is on which wheel ...