Tyre Pressures

[Martskoda]

Can someone explain to me what this means in plain English please! The reason being, over the weekend the tyre pressure warning came on as I was driving along. I checked the tyres and they looked okay, no obvious punctures. Yesterday after work I went to a tyre place near where I work. They had the front tyres off the car and checked everything, all they could say was they were a bit low on pressure. So they inflated the tyres to right pressure (32psi front and back, their words!) and off I go! Today after work warning comes on again! Check pressures!  So I call into a different branch of the same company and they check tyres. Their conclusion?! Over inflated!  They said they had just replaced there gauges with digital ones as the old ones were giving false readings! Perhaps this was the problem at their other branch...... I get this every time I get the tyres checked. Wrong pressures! Does anyone else get this?! It does my head in, when you leave it to “experts” and they are all different. 

[john999boy]

You also need to reset the monitoring system to let the car know that your tyres are at the correct pressure.

BTW this needs doing when they are cold.

Edited 13 August, 2019 by john999boy

[Martskoda]

Thanks! Sorry forgot to say they did yesterday and today, though admittedly they weren’t cold especially today!

[shyVRS245]

If you have the 17" alloys with 225/45 tyres 2.2bar or 32psi looks about right. Like John said I sometimes get these phantom warnings from the TPMS then after checking with my Michelin (well worth the investment) tyre pressure gauge/foot pump I reset it in the menu and all is good again.

[Ootohere]

@Martskoda

Are you resetting the TPMS each time the pressures are being set?

[Martskoda]

They have been reset each time by the garage. They know what they are doing!

[john999boy]

3 minutes ago, Martskoda said:

They have been reset each time by the garage. They know what they are doing!

So to be 100% correct - did you see them do this on the infotainment screen?

[Martskoda]

7 minutes ago, john999boy said:

So to be 100% correct - did you see them do this on the infotainment screen?

I asked them to do it yesterday, so I presume they did and today I saw him do it. The funny thing is the guy yesterday said 32psi all round but today it was 34psi!

[Kenny R]

14 minutes ago, Martskoda said:

I asked them to do it yesterday, so I presume they did and today I saw him do it. The funny thing is the guy yesterday said 32psi all round but today it was 34psi!

 

45 minutes ago, Martskoda said:

Thanks! Sorry forgot to say they did yesterday and today, though admittedly they weren’t cold especially today!

You’ve answered your own question. If the tyres were checked today when warm you’d expect the pressure to be higher than what they were yesterday when cold.

[john999boy]

21 minutes ago, Martskoda said:

I asked them to do it yesterday, so I presume they did and today I saw him do it. The funny thing is the guy yesterday said 32psi all round but today it was 34psi!

Cold pressure will be lower than hot pressure.

Anyway, getting back to your original question. That chart shows the front and rear cold pressures for whatever size tyres you have and dependant upon the number of people & luggage. Use the bar settings (2.2 etc) as all tyre gauges will show that.

It really isn’t something that requires a tyre centre visit to do. 

[KenONeill]

Diesel - No Biodiesel

 

Tyre pressures: To get PSI, Bar * 15, so 2.2 bar is 33 PSI for example.

[Ootohere]

The simple thing is when happy with the tyre pressures is 'set the TPMS yourself and don't leave it to others.

& check them regularly and rest the TPMS when you do.

[BoxerBoy]

Well that should fully answer the question. It ain’t rocket science.

[Rodge]

On 13/08/2019 at 20:37, Martskoda said:

I asked them to do it yesterday, so I presume they did and today I saw him do it. The funny thing is the guy yesterday said 32psi all round but today it was 34psi!

 

The TPMS doesn't really care what the pressures are when you reset it. All it looks for is changes in tyre pressures relative to each other. And very roughly, every 10 °C change in temperature will change the tyre pressures by about 1 psi.

 

The data plate in the OP says that anything between 32 and 36 psi is fine for the front tyres and 32 to 46 psi at the back, depending on loading. As far as I remember, mine also recommends 36 psi as being more economical.

 

I always set mine a bit high anyway to allow for deflation over time. If you set the pressures exactly then a week later they will be slightly low and need pumping up again.

[Ootohere]

It looks for a difference in the rotations from when the TPMS was set.

You can set the tyres at different pressures, put on different sized wheel / tyre like the spare and reset and it will log and register.

 

The type of system it is was for 'Run Flat' tyres and warning drivers that there was a deflation.

It is as basic as it can be and does the job if people bother to check what that is, set pressures and reset the TPMS.

 

Also check tyre pressures regularly and not rely on the TPMS, because if the pressures drop pretty much the same on all corners there might well be no warning.

 

As to pressures and heat, some warning are because of wheel bearing overheating or calipers binding and a wheel / tyre overheating and the circumference changing.

[flybynite]

7 hours ago, Rodge said:

All it looks for is changes in tyre pressures relative to each other

 

I think it is a bit cleverer than that. When winters go on/off it sets off TPMS showing all 4 tyres in orange on infotainment if I forget to reset it

[OldBoyScout]

I think my TPMS must have had a software update, maybe when car was serviced last year, as the warning now says which tyre is affected where previously it didn't say. This is on a 65 plate Scout. I have had a few false alarms, including 2 going over the summit of Rannoch Moor, about a year apart. I think the system may be affected by low outside air pressure at high altitudes. I have had more false alarms than genuine ones.

 

If I get a warning, and it is not a good place to stop and check pressures and pump up the tyres, I stop and have a quick look at the tyres to see if there is any visual damage or deflation. If the tyres look OK, I reset the system to tell it that the pressures are correct. I can then drive on to a safer place to check the pressures properly knowing that if any pressure is being lost I will get another warning.

[KenONeill]

On 16/08/2019 at 12:29, OldBoyScout said:

false alarms, including 2 going over the summit of Rannoch Moor

That's only 348m AMSL; by that argument TPMS should alarm several times going over some of the ALpine passes.

[OldBoyScout]

1 hour ago, KenONeill said:

That's only 348m AMSL; by that argument TPMS should alarm several times going over some of the ALpine passes.

Only if it's reset after the first and any subsequent alarm. Are you speaking from personal experience?

 

[nidza]

Guys, my car is pre FL 230, we've been travelling many times from <100m where I live, up to 1500-1800m, locally several times, plus last march to French Alps. I've never had false alarm.

 

Winters are 18", Summer 19". 

 

Really can't say I've noticed any strange behavior. TPMS reacted many times, each time with a reason. Unfortunately, I've lost many tires already due to f*ck*d up roads around here. Once it detected loss of pressure on all 4 winter tires, but it was due to severe temperature drop, more than 20 degrees overnight.

[OldBoyScout]

1 minute ago, nidza said:

Guys, my car is pre FL 230, we've been travelling many times from <100m where I live, up to 1500-1800m, locally several times, plus last march to French Alps. I've never had false alarm.

I'm just hypothesising from my own experience which is obviously different from yours. Are you saying you have never had a false alarm at all, or just nothing related to altitude?

 

[nidza]

@OldBoyScout, no false alarms ever, but underlined I have been many times on high altitudes, which also never has triggered a TPMS alarm.

 

Do you go offroad? As I see in your profile, you drive Scout, so if you go offroad, maybe you can have wheel vibrations which system may misinterpret as loss of air. Principle of the system is mostly relying on torsional vibrations. 

[OldBoyScout]

I occasionally go down some mildly rough unmade tracks, but have not had any TPMS alarms while doing so. Seems my altitude theory is probably wrong, but at least I have received some feedback. I guess Rannoch Moor is just a spooky place. 

[3rdoctavia]

Hi all,

From what i know, although i may be wrong , there is an advanced system which directly monitors tyre pressures via a fancy valve , and a more basic version which thr Octavia has. This uses the traction control to monitor excessive wheel rotations on any wheel. Once set the system knows how the wheels behave when they rotate but with a loss of pressure you have a wheel which throws up a continuous error by having to rotate more which the abs realises it cant correct . As a result is suggests that it might be low pressure as its ruled out excessive spin which it is able to control.

Think how it all works.

Cheers

[shyVRS245]

5 minutes ago, 3rdoctavia said:

Hi all,

From what i know, although i may be wrong , there is an advanced system which directly monitors tyre pressures via a fancy valve , and a more basic version which thr Octavia has. This uses the traction control to monitor excessive wheel rotations on any wheel. Once set the system knows how the wheels behave when they rotate but with a loss of pressure you have a wheel which throws up a continuous error by having to rotate more which the abs realises it cant correct . As a result is suggests that it might be low pressure as its ruled out excessive spin which it is able to control.

Think how it all works.

Cheers

Put simply it counts Red Herrings and when they reach 10 fishy level the warning light comes on to make you get the foot pump to check all Herrings are present and correct particularly useful when it's raining Cats & Dogs such as today's weather.