Tyre pressures have dropped

[AlanDL]

My 450h+ tyre pressure warning light came on this morning.  It is very cold, but not below zero, and the car is kept in a garage overnight.  The tyre pressure reading has dropped down for all tyres to 2.1, with the front offside tyre showing its 2.1 figure in orange.  The normal pressure is 2.4.  The tyres are run-flats, which I have never had before.  Is this drop in pressure purely to do with the weather.  If not, how are all tyres affected in the same way.  I did not notice this drop in the cold last winter, but then maybe the drop in pressure did happened but didn't trigger the warning: maybe the orange figure for the front offside means that that particular tyre has dropped a couple of fractions more than any last year and the other three tyres this year.  The pressures of two of the other tyres did go up to 2.2 in a very short trip this morning.  Are the tyre pressures more susceptible to the cold if they are run-flats?

[NemesisUK]

All just to do with the ambient temperature drop. Run-flats are no more susceptible than 'normal' tyres. Just Boyle's Law in action!

Inflate the tyres to the recommended pressures before the next journey

[HPS13]

Hi

I had the same issue this morning - TPMS light on, both front tyres showing 2 bar. It was -6 here and the car was parked on the drive. 

Will need to check the pressures soon (when it's a bit warmer!) 

[NemesisUK]

1 minute ago, HPS13 said:

Hi

I had the same issue this morning - TPMS light on, both front tyres showing 2 bar. It was -6 here and the car was parked on the drive. 

Will need to check the pressures soon (when it's a bit warmer!) 

You need to adjust the pressures to account for the drop in temperature, don't just wait for the temperatures to increase!

[Hayzee]

So in old money they have dropped from about 35 psi to 31 psi which must be enough to trigger the warning

[Ken R]

Below zero overnight here but no issues with tyre pressure.

[KW Lexus]

8 hours ago, NemesisUK said:

Just Boyle's

 

8 hours ago, AlanDL said:

My 450h+ tyre pressure warning light came on this morning.  It is very cold, but not below zero, and the car is kept in a garage overnight.  The tyre pressure reading has dropped down for all tyres to 2.1, with the front offside tyre showing its 2.1 figure in orange.  The normal pressure is 2.4.  The tyres are run-flats, which I have never had before.  Is this drop in pressure purely to do with the weather.  If not, how are all tyres affected in the same way.  I did not notice this drop in the cold last winter, but then maybe the drop in pressure did happened but didn't trigger the warning: maybe the orange figure for the front offside means that that particular tyre has dropped a couple of fractions more than any last year and the other three tyres this year.  The pressures of two of the other tyres did go up to 2.2 in a very short trip this morning.  Are the tyre pressures more susceptible to the cold if they are run-flats?

I have same issue tonight (-1 degree) with type pressure warning light on and orange light for front offside type  at 2 bar ( but other 3 types also at 2 bar with no orange light ) not sure if a punch on the front offside type ??

[KW Lexus]

 

My UX250  have same issue tonight (-1 degree) with type pressure warning light on and orange light for front offside type  at 2 bar ( but other 3 types also at 2 bar with no orange light ) not sure if a punch on the front offside type ??

 

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[Rabbers]

Without being asked to do so, my tyre guy, when fitting my winter tyres, adds 0.1-0.2 BAR bringing the recommended pressures of 2.5 all-around in the RC's case to 2.6-2.7.  This has always proved sufficient for them not to drop below 2.2 at worst even after overnight parking in the open at temperatures perhaps as low as -10°C.

[Al D-Much]

17 hours ago, Hayzee said:

So in old money they have dropped from about 35 psi to 31 psi which must be enough to trigger the warning

Yep, that's about 11% drop, TPMS will trigger anything above a 4% drop.
This time of year, and especially with the temperature dropping quite suddenly, this will be a common occurrence.

Always happens to mine but only 1-2 psi (approx. 3% - 6%), 11% does seem a high drop to me. (If that makes sense)