TPMS

[thamestrader]

Having collected my Karoq last Friday, I've noticed that everytime I start it up the TPMS system is asking me to SET the Tyre Pressures, so I touch the SET button and then the Confirm. But it asks me again the next time I start the car. I've checked all the pressures and they are 2.4 Bar on all 4 wheels.  We have the same system on our 2015 Fabia and that does not behave in this way.

 

Any thoughts or suggestions gratefully received.

[Ootohere]

Are you touching it long enough until there is a confirmation that you have.  A noise or a light? What does the owners manual say the procedure is for the Karoq? 

[Rgsmg53]

I have exactly the same problem. I've tried everything I can think of. No joy.

 

Being old school, I'm not wasting any more time on it. Just gone back to my old regime of regular checks with a good quality pressure gauge. I also believe I'm experienced enough to feel a big discrepancy developing unexpectedly, especially with the low profiles. No doubt someone will argue with that approach.

[BTandSid]

Was going to say much the same as Ootohere. We’ve a Karoq and seem to recall that after we had the AA deal with a flat I reset the TPMS but it flagged up again. Think I went in and reset it again and it cleared so perhaps you need to press set or hold the key longer? Sorry if it sounds a bit vague but short of deflating a tyre I’m not sure how I could reproduce the process

Edited 1 May by BTandSid

[Rgsmg53]

Just re-read my online manual yet again and see it recommends re-setting TPMS once a year /10k km.

 

So I'll give mine another go tomorrow.

 

How about you @thamestrader? Didn't mean to hijack your thread. Apologies.

[Ootohere]

Strange if that is what the manual says.  Very different from regularly checking tyre pressures and checking and resetting the TPMS.    All 4 tyres can lose pressure and the TPMS not flag that.    Always check tyres / pressures and do not wait for warnings.   Then there is changing pressures to suit the load carried.  Maybe only changing the rears.   Reset the TPMS.    It is just a simply clever thing.    Skoda owners manual authors can be simply stupid.     PS, once a year / 10.000 km.    Odd.  Not once a year and 9,400 miles (10,000) like UK fixed servicing regimes.    This is Skoda / VW and crazy miles days.    Not unusual. 

Edited 2 May by Ootohere

[Rgsmg53]

Yes, I don't understand the logic of 'resetting' the TPMS once a year / 10k kms either.

 

To me, TPMS seems like another unnecessary piece of 'tech'. As you rightly say, all 4 tyres could lose pressure over time and, if the tyres are all in similar condition, then I would expect any gradual pressure loss to be at a very similar rate. My guess is the real driver for TPMS is warning of a 'sudden' onset of a puncture. But in 50 years of motoring, I can 'feel' a sudden puncture long before it goes completely flat (ie ruins the tyre). My Sportline does not have smart tyre valve caps so obviously this type of TPMS does not measure pressure directly. The only way I believe it can do it therefore is by comparing the rolling diameters of each tyre and of course this will depend on tyre wear and (theoretically) on tyre loading. 

 

Anyway, I have dutifully done my type pressure checks again today and added a couple of PSI to each tyre according to my pressure gauge (Bourdon tube type). The need for a couple of PSI in each tyre is almost certainly due to the ambient temperature being a trifle chilly for early May!

 

Have now reset the TPMS in accordance with the manual and on-screen instructions. Final message on screen showed "Tyre pressures saved". We'll see what happens. 

[thamestrader]

Thanks for the replies - as far as I can tell I'm doing the same as you folk as I'm getting the Tyre Pressures saved message.  Its almost as though it forgets that the pressures have been saved when the car is started after being parked. I will have to monitor to see if this only happens overnight or after a certain time as its not consistently after everytime the car has been locked.

[Rgsmg53]

I suppose if I was really brave, I could let 10 PSI out of one tyre and then drive it up the road for a mile or so to see what happens........................................

[Routemaster1461]

4 hours ago, Rgsmg53 said:

My guess is the real driver for TPMS is warning of a 'sudden' onset of a puncture.

 

The indirect type of TPMS isn't really suitable for sudden losses of pressure, as it relies on the system noticing the faster rotation of a wheel over an unknown lenght of time. A sudden loss of pressure will probably be too quick for the indirect system to recognise.

Similarly the indiect system will not warn you if a tyre has gone flat overnight as the system requires input from the ABS system. The direct system should though.

[Ootohere]

The TPMS was brought in for the likes of BMW / MINI,s and others with Run Flat tyres and muppets that never even noticed a puncture.

 

Simple to see if the system works. Let a tyre down only 5 psi from when the TPMS was set.

 

The tyres can be art different pressures around the car and set. 

The Fronts can be different from the rears and set.      You can put on a slightly different size spare, reset the TPMS and get no warnings.

There are some cars that might have issues, disable CC / ACC etc.   Superbs commonly. 

[croquemonsieur]

I've never had any malfunction of the TPMS nor problems resetting it on my Karoq and am actually glad the car has this facility.  It did come on once and told me the problem tyre which turned out to have a slow puncture - I couldn't detect that in the way the car handled.  So after that I checked that tyre weekly and pumped it up regularly, which was a bit of a bind until I changed all the tyres to the all weather variety.  I know... I should check the tyres weekly anyway.  Anyway recently I thought I'd better check the new set of tyres after too long a period over winter and they were all too far down by quite a bit, so I got the electric pump out.  I might consider getting the tyres filled with nitrogen soon, like I did on my previous Yeti - they hardly ever needed pumping up after that and then it only cost £5 for all 4 tyres.  I do actually set the tyres near the lowest recommended pressure to keep the ride as smooth as possible, so yes I should be keeping an eye on  the pressures more frequently, naughty!!

[Ootohere]

Nitrogen filled does not mean there is no loss of pressure.  Did they remove all the normal air to fill with nitrogen?    I do know all the bumff on not passing through tyre walls so fast.     Amazingly many millions of tyres with the compressor filled air lose no pressure over years. Often new valves are just what are needed. 

Edited 2 May by Ootohere

[croquemonsieur]

They were supposed to remove all the air, so I hope they did - they wouldn't let me into the workshop to see what's going on.  Actually, my experience was that afterwards the tyres didn't lose pressure anything like as quickly.  Also the nitrogen doesn't expand as much when hot, I recall reading somewhere + all the moisture in ordinary air filled tyres is absent with nitrogen.  Anyway they fit nice green caps to the valves, which makes me feel smug.

[Ootohere]

Very true.  Nissan GTR on a track you do not want H2o in your tyres.   So they purge all air from your tyres, then fill with nitrogen and if you do need to put more pressure in you go to them and put in nitrogen.   If you let the pressure down due to load or weather or increase you go to them.    Amazing value.   When checking pressures you never ever let a little nitrogen escape.  

[J.R.]

4 hours ago, Routemaster1461 said:

The indirect type of TPMS isn't really suitable for sudden losses of pressure, as it relies on the system noticing the faster rotation of a wheel over an unknown lenght of time. A sudden loss of pressure will probably be too quick for the indirect system to recognise.

 

The time constant certainly is known to the Controller and the system reacts very fast to a puncture or deflating tyre, it also reacts very well to slow punctures, I lingered on with one for the last year to get the maximum life out of my old tyres and it would remind me 10 days after I last reinflated the tyre, I would do a visual check then ignore it and do a reset, after about another 7 days the 2nd warning and by then the tyre warranted reinflating, it was remarkably consistent.

 

Today I removed the winter wheels I had been driving on while fitting my new tyres, they had no punctures and were correctly inflated, I fitted the new ones correctly inflated, significant difference in rolling diameters between the worn 205/55/16s and the new 215/60/16s but each set all 4 tyres the same rolling diameter, I forgot to reset the TPMS and drove 8 miles without a TPMS warning whereupon I did a reset.

 

For a simple yet highly reliable system it is very accurate indeed. If you dont believe me and still think it is slow to react then let down one of your tyres partially and drive away, you probably wont even get into second gear or have straightened out the steering wheel before you get a warning.

Edited 2 May by J.R.

[J.R.]

45 minutes ago, Ootohere said:

So they purge all air from your tyres, then fill with nitrogen

 

Purge with what?

 

The only way to remove most of the air is to pull a vacuum and they don't do that because the tyre would unseat from the bead after contorting so much that the plies would break.

[J.R.]

However you have got me thinking, I need a more effective beadbreaker than the one on my tyre changing rig and I happen to have a vacuum pump!

[Paws4Thot]

1 hour ago, croquemonsieur said:

I recall reading somewhere + all the moisture in ordinary air filled tyres is absent with nitrogen.

I can do you a good price on Tower Bridge...  

Spoiler

"Ordinary air" is 80% nitrogen.

 

[Ootohere]

@J.R.  yes I know they did not actually purge the tyre on the rim with a valve on.  But we know what they do as far as taking money from willing victims. 

[J.R.]

We have a name for that in my country "Pigeon" willing victim is the exact definition, how the phrase came about is rather unpleasant.

Edited 2 May by J.R.

[Sanqhar]

I have never understood filling with nitrogen after all air is 78% nitrogen anyway. 

 

tom

[croquemonsieur]

So up to 22% could ultimately leak out!!!! - sounds like quite alot.  Come-on.... we're only talking about £5, though admittedly a few years ago + free topping up if you could be bothered to go back to the same place.  I imagine the weight of air in a fully inflated tyre is many times that in a tyre at atmospheric pressure, so most of the air and accompanying moisture would be removed when initially deflated before refilling with nitrogen.  Twas worth a try.

[Routemaster1461]

Nitrogen filling is basically a scam. It is a fact that the oxygen molecules are slightly smaller than the nitrogen molecules, and will leak out faster. But it is such a minute difference that in practical terms it is negligable. And that is it in terms of facts. The basic laws of physics and chemistry mean that nitrogen doesn't heat up faster or slower than air, or that there is a difference in compressibility, therefore comfort is not improved or made worse.Any other difference claimed is that it will prevent degradation of the inside of the tyre, but tyres will wear out and degrade on the outside faster than inside. 

Nitrogen fill is require on aircraft tyres annd is used on Formula 1 tyre. Fr anything else you are paying for no benefit and money is wasted. Try reading about it on a recognised site like AA or RAC, not a tyre company site.

 

In fact here is what one of the tyre suppliers, Protyre, say. 

 

'In our experience, the benefits of inflating tyres with nitrogen are so imperceptible that justifying the inconvenience and expense can be hard to do. It is generally more worthwhile investing in a tyre pressure gauge or visiting your local Protyre garage who can perform a free tyre check for you and advise on the correct tyre pressures for your vehicle.' 

[J.R.]

2 hours ago, croquemonsieur said:

So up to 22% could ultimately leak out!!!! - sounds like quite alot.

 

How many thousands of years are you planning to live?

 

I have dived on WW2 Jeeps and troop carriers at Million Dollar point and the tyres were still inflated even though there were gaping rusted holes in the rims, ditto in the cargo hold of the President Coolidge at 67m, most tyres still had the full amount of air although reduced volume due to the 6.7 bar external pressure.

 

2 hours ago, croquemonsieur said:

I imagine the weight of air in a fully inflated tyre is many times that in a tyre at atmospheric pressure, so most of the air and accompanying moisture would be removed when initially deflated before refilling with nitrogen.

 

No need to imagine when you have Boyles law, the weight of the air were you to find a scientific instrument capable of measuring such a small amount in the tyre inflated to 2 bar guage pressure = 3 bar absolute would be 3 times the weight of the air in the deflated tyre at 1 bar atmospheric pressure. You should be using volume not weight.

 

Why are you concerned about moisture content?