TPWS tolerance - 2-3 PSI?

[RobN-RG]

Hi, 

What is the expected tolerance of the tyre pressure warning system?  Cleary not this week, but during the winter if the PSI dropped to 26, I get a warning about the tyre pressure - this would go off if I drove for a few miles as the tyres warmed up.  Surely it should only have a paddy if the pressure really goes down?  If I inflated enough to clear the error, it was then too high after a drive.

[Paul john]

Always set Tyre system at cold as in normal driving it rises by 4psi (greatly discussed here)

[MikeSh]

2 hours ago, RobN-RG said:

but during the winter if the PSI dropped to 26

Yes. The pressure changes with temperature. Tyres generally lose a little pressure over time, so with the lower temperatures as we go into winter you need to add a bit of air every few weeks to compensate. In spring the higher temperatures tend to offset the loss with time, so things may stay in balance for a while. But you need to check regularly. It's not something you should leave for the annual service.

As @Paul john says you need to set the tpms at the specified cold pressures. Then check them regularly, especially from September through February, to keep them at the correct cold pressures. 26psi certainly sounds low for most cars, so the tpms is right to tell you to get your act together.

[TonyHSD]

I see the most breakdowns on uk motorways during summer time are blown out tyres. Sometimes so often it’s like at least one car every 2-3 miles. , especially when is hot weather  like 25C° and over. 
The reason is only one., people tend to drive with under inflated tyres, common practice. 
Tyres pressures checks more often needs to be done and not waiting for any dashboard warnings or reminders., these are for emergency use when you had a puncture and you can’t feel it and keep driving, the tpms will detect pressure drop, warn you and you can pull over and check. 

[Cyker]

On 6/26/2024 at 8:50 PM, RobN-RG said:

Hi, 

What is the expected tolerance of the tyre pressure warning system?  Cleary not this week, but during the winter if the PSI dropped to 26, I get a warning about the tyre pressure - this would go off if I drove for a few miles as the tyres warmed up.  Surely it should only have a paddy if the pressure really goes down?  If I inflated enough to clear the error, it was then too high after a drive.

There is no such thing as 'too high after a drive' - As everyone has said, the rated pressures are when the tyres are cold only.

It's completely natural for them to go up several psi while being driven and there's nothing wrong with that; In fact it reduces the chances of getting a puncture as the higher pressure resists tyre flex which will limit how much they heat up.

Too-low a pressure means there will be a lot of tyre flex which in turn causes heat and too much heat will cause the tyre to fail.