Under inflated tyre warning sign

[JoePeddos]

On Wednesday about 5 miles from home the tyre warning sign came on I pulled off the road and checked the tyre pressures 2 were 35 psi and 2 were 35.5 external air temperature 9.5C. Before the sign came on I had traveled about 20 miles half on motorways. I reset the tyre pressure monitor and so far so good.

Any one else had a similar warning sign come on and tyre pressures were ok Joe

[Ootohere]

But what pressure were the tyres last time the TPMS was set, and how long ago was that, or how many miles ago.

 

Always be sure that one brake is not binding so a wheel getting hot and the tyre so the TPMS giving a warning.

Best check the tyres again when cold and see the pressures.

[Kobayashi]

^^If the TPMS was last pressed at 25-26psi etc.. then it may well come on a hot run 35psi, ive read it has happened as well when travelling low to high ground

[bertJ]

Yes, this happened to me on a Passat during some hot weather a few years ago. The pressure on all the tyres had increased by about 3ibs so I reset the pressure warning and it never happened again. This pressure warning system seems to be very crude and prone to false alarms. Just check your pressures with a good tyre pressure gauge and reset the warning system if it happens again. 

[FabiaGonzales]

When i check pressures, i either, do them when they are cold on a hot day, or when they are warm on a cold day. That way it somewhat averages out so cold days and hot days don't trigger the sensor. Never had it go off until i got an actual puncture

[rum4mo]

With the OP's tyre pressures being so close all round, if they had been all the same when the TPMS was previously reset, then this would just be the usual false warning. I've only had one of my wife's 2015 Polo in 3.5 years 26K miles and strangely only one on my 2011 S4 which I know has a very slight leak on one front winter wheel valve body/alloy wheel hole.

[JoePeddos]

23 hours ago, Skoffski said:

But what pressure were the tyres last time the TPMS was set, and how long ago was that, or how many miles ago.

 

Always be sure that one brake is not binding so a wheel getting hot and the tyre so the TPMS giving a warning.

Best check the tyres again when cold and see the pressures.

The car was serviced + mot and a new front tyre fitted due to a fault in the sidewall 2 weeks ago. The tyre pressure recommended is 2.4 bar all round which i converted to 35psi. Its possible the thicker tread of the new tyre may have caused the error and i never thought to check the pressure when i got the car back from the garage. Joe 

 

[vc-10]

The system doesn't actually measure the pressure, it measures the relative diameters of the 4 wheels. If a tyre is flat then the rolling diameter is reduced, and the system measures this with the ABS speed sensors. This means it doesn't need costly sensors in each wheel, instead using sensors which are already there for other systems, with the downside being that it's fairly crude and is more intended to alert you that something's gone wrong than to accurately measure the pressure. Changes in altitude and temperature will affect all 4 wheels equally, so I doubt there would be any issues caused by that. 

[Ootohere]

@JoePeddos

So seeing as you never reset the TPMS and likely the tyre fitter never that warning did exactly as it should, and you checked the pressures and reset the TMPS.

 

The Owners Manual tells you to test, so that will be regularly, when checking tyre pressures, adjusting pressures and when changing tyres.

 

If you fit the spare which is a slightly different size you can reset the TPMS and get no warnings, but on cars with ACC etc it disables that.

[gumdrop]

I have had several warnings from this system, mostly temp. increases on one tyre.

BUT it pays to look carefully, two punctures were caused by screws and one by

a piece of wire all in the sidewalls so this meant new tyres were required.

I only found the causes by running my hands around the inside tyre walls.

[FabiaGonzales]

Recently reset my tyres pressures.

 

Set all to 32 PSI when cold at 20c ambient. 30 seconds after setting off, the TPMS kicks off screaming "check all tyres". So at least now we know what it does if they all go way off.