Correct tyre pressure for low temperatures?

[Hayzee]

5 hours ago, philip42h said:

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 ... 

That's not my experience. When my TPMS warning came on, one wheel showed orange and the pressure for all 4 wheels was displayed. It was the displayed wheel which was at fault.

[Strangely Brown]

2 minutes ago, Hayzee said:

That's not my experience. When my TPMS warning came on, one wheel showed orange and the pressure for all 4 wheels was displayed. It was the displayed wheel which was at fault.

I'm not sure that feature exists on the HEV?

[ernieb]

It’s a PHEV feature, exact individual tyre pressures and error light.

[philip42h]

Yet another strange, and somewhat inexplicable, difference between the HEV and PHEV! 🙂

[Cyker]

That can't be right... I thought all the new models had a full TPMS sensor readout. Even mine does and it's a Yaris!!  

It re-learns which sensor is on which wheel every time I power the car up, and updates the pressures at regular intervals (Which is why I was saying I got a bit scared in summer watching it climb from 38 to 47 psi while I was hoofing it up the motorway!   )

I'm sure the RAV4 HEV must do this too as I can't see them going to the expense of using a different TPMS system for such similar models...!

[Strangely Brown]

1 hour ago, Cyker said:

I'm sure the RAV4 HEV must do this too as I can't see them going to the expense of using a different TPMS system for such similar models...!

Where do I find it? I thought I had been through all of the displays and I have not come across it.

[Cyker]

On mine, if you go to the display that shows the HSD power flow between the wheels and Battery etc. on the dash display (Not the head unit), it's either left or right of that.

 

[philip42h]

33 minutes ago, Strangely Brown said:

Where do I find it? 

On a PHEV (or Mk4 Yaris apparently) but not on a HEV ... 🙄

[FROSTYBALLS]

Returning to the topic title, aren't the correct tyre pressures for low temperatures exactly the same as the tyre pressures for higher temperatures - ie. those on the tyre pressure sticker/plate on the car.

[philip42h]

4 minutes ago, FROSTYBALLS said:

Returning to the topic title, aren't the correct tyre pressures for low temperatures exactly the same as the tyre pressures for higher temperatures - ie. those on the tyre pressure sticker/plate on the car.

Yes, they are ...

[jadatis]

Made list for pressure/temperature relation. 

In the middle the cold filled pressure at 21degrC/ 70degrF, in front degrC/psi change, and behind degrF/psi change. 

So yust search the cold pressure you filled, and remember the degr per psi, is rounded to 0.5 degr, acurate enaugh to work with. 

If you use it for 60 degrF/ 15 degrC filled, it wont give dramatic differences. 

If wanted I can give you text I used for american RV forum with why I think you can yust let the pressure vary with temperature safely, if calculated back to those indexed temperatures. 

degrC/psi/psi21C70F/degrF/psi

8,5    C/psi/    20    psi/    15,5F/psi
8    C/psi/    21    psi/    15    F/psi
8    C/psi/    22    psi/    14,5F/psi
8    C/psi/    23    psi/    14    F/psi
7,5    C/psi/    24    psi/    13,5F/psi
7,5    C/psi/    25    psi/    13,5F/psi
7    C/psi/    26    psi/    13    F/psi
7    C/psi/    27    psi/    12,5F/psi
7    C/psi/    28    psi/    12,5F/psi
6,5    C/psi/    29    psi/    12    F/psi
6,5    C/psi/    30    psi/    12    F/psi
6,5    C/psi/    31    psi/    11,5F/psi
6,5    C/psi/    32    psi/    11,5F/psi
6    C/psi/    33    psi/    11    F/psi
6    C/psi/    34    psi/    11    F/psi
6    C/psi/    35    psi/    10,5F/psi
6    C/psi/    36    psi/    10,5F/psi
5,5    C/psi/    37    psi/    10    F/psi
5,5    C/psi/    38    psi/    10    F/psi
5,5    C/psi/    39    psi/    10    F/psi
5,5    C/psi/    40    psi/    9,5    F/psi
5,5    C/psi/    41    psi/    9,5    F/psi
5    C/psi/    42    psi/    9,5    F/psi
5    C/psi/    43    psi/    9    F/psi
5    C/psi/    44    psi/    9    F/psi
5    C/psi/    45    psi/    9    F/psi
5    C/psi/    46    psi/    8,5    F/psi
5    C/psi/    47    psi/    8,5    F/psi
4,5    C/psi/    48    psi/    8,5    F/psi
4,5    C/psi/    49    psi/    8,5    F/psi
⁸4,5    C/psi/    50    psi/    8    F/psi
4,5    C/psi/    53    psi/    8    F/psi
4,5    C/psi/    54    psi/    7,5    F/psi
4    C/psi/    55    psi/    7,5    F/psi
4    C/psi/    58    psi/    7,5    F/psi
4    C/psi/    59    psi/    7    F/psi
4    C/psi/    63    psi/    7    F/psi
3,5    C/psi/    64    psi/    6,5    F/psi
3,5    C/psi/    70    psi/    6,5    F/psi
3,5    C/psi/    71    psi/    6    F/psi
3,5    C/psi/    75    psi/    6    F/psi
3    C/psi/    76    psi/    6    F/psi
3    C/psi/    77    psi/    6    F/psi
3    C/psi/    78    psi/    5,5    F/psi
3    C/psi/    86    psi/    5,5    F/psi
3    C/psi/    87    psi/    5    F/psi
3    C/psi/    91    psi/    5    F/psi
2,5    C/psi/    92    psi/    5    F/psi
2,5    C/psi/    96    psi/    5    F/psi
2,5    C/psi/    97    psi/    4,5    F/psi
2,5    C/psi/    109    psi/    4,5    F/psi
2,5    C/psi/    110    psi/    4    F/psi
2,5    C/psi/    115    psi/    4    F/psi
2    C/psi/    116    psi/    4    F/psi
2    C/psi/    126    psi/    4    F/ps
 

Dont have a Toyota, registered to give this info. 

Call myself " pigheaded Dutch selfdeclared tyrepressure specialist" 

[philip42h]

11 hours ago, philip42h said:

11 hours ago, FROSTYBALLS said:

Returning to the topic title, aren't the correct tyre pressures for low temperatures exactly the same as the tyre pressures for higher temperatures - ie. those on the tyre pressure sticker/plate on the car.

Yes, they are ...

The OP pretty much answered his own question in his first post. According to information on the Internet tyre pressure varies by about 0.1 bar (1.5 psi) for every 10 degrees C of temperature change. Exact numbers quoted vary across the different sources but 0.1 bar / 1.5 psi per 10 degrees seems a reasonable average / approximation.

That would mean that if you set your RAV4 tyres to a correct 33 psi in the summer at 20 degrees, they could well be only 30 psi in the winter at 0 degrees C. (And possibly a little lower as a result of losses in the meantime). According to the specifications you should reinflate the tyres to 33 psi. 👍

Running at these slightly lower pressures in winter shouldn't do any harm and might give marginal benefits it terms of grip on the snow - but is not recommended.

Equally, a drop of only 3 psi (~9%) won't be sufficient to trigger a TPWS warning - assuming that the TPWS system is correctly set at 33 psi in the first place. If you do get a TPWS warning then either the tyres are at well below 30 psi or the TPWS system is not correctly set. There have been a sufficient number of reports to suggest that the TPWS system may not be correctly set at PDI and it is probably advisable that RAV4 owners do so for themselves - you only have to do it correctly once and it will then stay good (until you change wheels / TPMS valves).

We really ought to check and adjust our tyre pressures at least once each season - i.e. spring, summer, autumn and winter - to mitigate against seasonal changes in ambient temperature (and, of course, any actual losses).

[jadatis]

There is a difference of opinion about if cold pressure has to be filled at ambiënt temperature, whatever it is, or has to be calculated back to an indexed temperature.

Even about that indexed temperature there is discussion, 21, 20, 18 and even 15 degr C. I have seen written. 

I am in the camp of calculating back, and why, I described in a text I used for a topic on american RV forum. 

Written in degrF and psi and 80psi used as example, has to be translated to the pressures for this forum, but the idea is the same. 

Trickering TMPS is a secundary problem. This can easyly be implemented in the software of tmps, using outside temperature, wich newer cars also have sensor for. 

For motorcycles I read about tmps giving pressure, calculated back to 18 degrC. 

 

[Sealiedog]

On 12/16/2022 at 8:35 PM, Cyker said:

That can't be right... I thought all the new models had a full TPMS sensor readout. Even mine does and it's a Yaris!!  

It re-learns which sensor is on which wheel every time I power the car up, and updates the pressures at regular intervals (Which is why I was saying I got a bit scared in summer watching it climb from 38 to 47 psi while I was hoofing it up the motorway!   )

I'm sure the RAV4 HEV must do this too as I can't see them going to the expense of using a different TPMS system for such similar models...!

My hev doesn't show individual wheels, it just shows that there is low pressure somewhere.

[jadatis]

Then you most likely have indirect system. 

Uses the sensors for ABS, and reacts if rotationspeed difference between the wheels on an axle. 

This year I had a signal of to low pressure, but pressures where OK. 

Resetbutton used but came back. 

Was a hanging brake wich heated up the tire inside air trough the rimms. 

This gave higher pressure, so lesser deflection, so more rolling-circumference, and by that difference in rotation speed, so the other way around as when one low pressure tire. 

Burned my finger touching the rimm. 

Had to repair it by mounting a new brake-claw. 

[FROSTYBALLS]

9 minutes ago, jadatis said:

Then you most likely have indirect system. 

The only European market Toyota produced since TPMS became a mandatory fitment on all new vehicles (November 2014), that had an indirect system was the Aygo.

Direct systems don't always show which wheel is affected by a pressure loss warning. 

[Dippy]

Bought a tyre pressure gauge before my 700 mile trip, to get it right. Car is 2008 DCAT, tyres are Michelin PS4 SUV.  Should be 2.2 bar all round. Set them to 2.2 when cold (outside temp perhaps 12C). Drove about 70 miles down the motorway. Pulled in at a service station to re check, expecting an increase with warmer tyres. Same pressure! 

[TonyHSD]

1 hour ago, Dippy said:

Bought a tyre pressure gauge before my 700 mile trip, to get it right. Car is 2008 DCAT, tyres are Michelin PS4 SUV.  Should be 2.2 bar all round. Set them to 2.2 when cold (outside temp perhaps 12C). Drove about 70 miles down the motorway. Pulled in at a service station to re check, expecting an increase with warmer tyres. Same pressure! 

What type pressure gauge have you used for these measurements? Some aren’t exactly accurate and small deviations might not be recorded. The pressure after that drive should have been at least 2.25 bar or more. 

[Dippy]

Basic one, needle round a dial. I don’t believe it would show a difference of 0.05 bar. Maybe I was expecting +0.1 or +0.2. 

[jadatis]

Then if both measurements where with that same gauge, only explanation can be paralax reading error. 

[TonyHSD]

I use Michelin digital tyre pressure gauge and it works very well plus shows even smallest numbers of deviation. For example I keep my tyres front at 2.3bar often I play with pressures little but up or little bit up depending on season and air temperatures. In winter I tend to keep close or exact to 2.3 bar where in summer time 20C° and above I can set at 2.35bar and the car feels great on the road. The gauge itself is set to show difference of up to 0.05 as OK , anything more than this shows as too much or too little and to adjust. In general the best way to judge if the tyre pressures are set correctly is by how the car feels when you drive., too soft - under inflated, too hard over inflated. The ideal pressures are those in the middle. 

this is mine, it’s an old now and not officially available but this one is the equivalent 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

[Roy124]

Soft rear tyres probably less indicative. 

I check using the onboard display and then an AA Digital compressor.  Preset the required pressure and it does the rest. 

I just sold an unwanted Toyota inflation kit.  It only has an analogue gauge. For those that have the Toyota kit but haven't examined it, it is a two part kit. 

You attached the repair fluid container (must be correctly positioned) then attach the compressor to it and switch on. 

I suppose this is better than a pressurised can of inflation fluid as you can see it's the right pressure. 

[ernieb]

@TonyHSD, I use the same gauge, probably the best of the many I’ve bought over many years.

[Stivino]

This is how I check my tyre pressures;

1: Open driver's door.

2: Read the sticker. 

3: Set pressures to whatever is says on the sticker using my 30 years old gauge with a needle. 

4: Forget about until the next time.

That system has served me and millions of others well since the invention of pneumatic tyres.

HTH.