I checked my tyre pressures on New Years Eve, found them all a bit low and topped them up; later on a short journey, the TPMS flagged one as low; when I got home, it had dropped about 0.5 bar so I topped it up again. When I checked it on 4th Jan, it hadn't lost any pressure and I couldn't see any damage or embedded screw heads etc. I did a few more short journeys that day with no TPMS warnings. By 6th Jan, it was completely flat. Today, I've pumped it back up and taken it to the local tyre fitters who can't find anything wrong! Any ideas?

I take it you topped them up NYE and also reset the TPMS.

 

Maybe a tear on the valve as you put air in & when the Tyre fitter checked for leaks they missed it was losing air there.

It was losing air someplace since you inflated the tyres,

 

?

Is the TPMS reset now when all the tyres are cold and at the pressures they are at?

 

Did the tyre fitter fit a new valve for you?

Edited 7 January, 20224 yr by roottoot

Sometimes pressure is lost through where the tyre seats on the rim.

Valve definitely a suspect, I have had them where the inner core was not properly bonded into the outer rubber sleeve but did not leak on the immersion test, however if tweaked sideways by hand the air leaked & this was also happening when driving.

 

Recently I had the core blow completely out of the inner tube on a trailer wheel, it was an old inner tube but had not been leaking, luckily I was not driving, I came out to find the tyre flat, when I went to reinflate it there was no Schrader valve & body in the inner tube, it was found several metres away.

Thanks all, good point about the valve. It wasn't replaced as they didn't find a leak there. I'll check it out.

 

The tyre place assures me that the tyre and rim are fine.

 

I did reset the TPMS each time I corrected the pressures, it has worked well on this occassion.

34 minutes ago, D402 said:

The tyre place assures me that the tyre and rim are fine.

As others, my first thought was of losing air through the bead "seal". This isn't always obvious with a "dunk tank".

The thing is that the OP is that all tyres had a pressure drop which as Tom sung is Not Unusual and why tyres need checked. 

Then after the pressures are increased one goes flat.

 

Time will tell what is the reason if nothing has been done other inflating again the one that was flat. 

2 hours ago, KenONeill said:

As others, my first thought was of losing air through the bead "seal". This isn't always obvious with a "dunk tank".

 

This was the issue with one of my tyres on my 16 year-old alloys pinched from a Fabia Bohemia, issue didn't show itself when the thing was placed in soapy water etc. The tyre fitters (was Budget in Ayr, then Tyre-City, and then Kwik Fit within a matter of weeks) just replaced the tyre free of charge.

Install Direct TPMS

-> https://www.briskoda.net/forums/topic/488740-my17-superb-retrofitted-with-direct-tpms/?do=findComment&comment=5487683

 

18 minutes ago, MartiniB said:

Install Direct TPMS

Why? The OP realises and agrees the fact of pressure loss. Direct TPMS is no better than indirect at locating the actual position of an individual leak.

12 hours ago, KenONeill said:

Direct TPMS is no better than indirect

Indirect can give false and late warnings

1 hour ago, MartiniB said:

Indirect can give false and late warnings

That is a deliberate and selective misquote. I repeat with additional emphasis " Direct TPMS is no better than indirect at locating the actual position of an individual leak".

@KenONeill

bla bla, bla bla

 

several times have seen

 

and

 

which exact tire has problem?!

 

first few warnings were false after checkout,

and there is result of ignore one true

 

 

alternative kits are enough cheep

-> model 2017. 53€
-> model 2018. 30€
-> model 2019. 27€
-> model 2020. 20€

 

 

55 minutes ago, MartiniB said:

several times have seen

Was that a nail through tread, a torn valve or a broken bead seal? All possible causes, and which it is is not detected by any TPMS.

Edited 8 January, 20224 yr by KenONeill

2 hours ago, KenONeill said:

Was that a nail through tread, a torn valve or a broken bead seal?

nothing of listed, Indirect TPMS reporting false alarms few times a year

 

I've sprayed soapy water around the valve and given it a good wiggle, there was no sign of any leak there. The tyre fitters did remove the tyre from the rim to inspect them and didn't find anything wrong. It hasn't lost any pressure since I drove home yesterday so I'm hoping that it's sealed properly this time.

 

We've had four VAG cars with indirect TPMS and they've all given false warnings after correcting pressures and resetting the system. It seems to need several resets before it stops giving these false warnings. On the other hand, when we've really had slow punctures, the TPMS has picked them up correctly before any further damage occurred, as on this occasion. It didn't detect a rapid deflation from sidewall damage from a pothole impact before I stopped to inspect it anyway though.

4 hours ago, D402 said:

The tyre fitters did remove the tyre from the rim to inspect them

Which is about enough to confirm my suspicion that the issue was a bad bead seal.

Strange to occur when the tyres have been inflated.

 

Strange or poor practice that a tyre fitter would remove a tyre and not also pull the valve, chuck it and put in a new one before refitting the tyre.

 

Strange things happen though.  

 

@D402 

was the tyre check done without you having to pass silver over the palm of the tyre fitter?

Edited 9 January, 20224 yr by roottoot

14 hours ago, roottoot said:

was the tyre check done without you having to pass silver over the palm of the tyre fitter?

Yes, they didn't charge me for the check although I'd happily have paid for what they did. The tyre is still up today but I've not driven far, longer journeys coming up tomorrow and next weekend.

I hjad a tyre which was deflating slowly and I couldn't find the issue. Turned out it was one of the little paper stickers that some manufacturers put on the bead of the tyres. This one had split leaving a little channel that allowed the air to escape.

Nearly two months on and I've had no further problems, reseating the tyre must have cured the leak.