Tyre Pressure monitoring

[kazand]

Having had this system on several VAG cars, up until recently I would have agreed with people for whom the system has worked correctly. However, current work motor ( 16 Passat) has developed an annoying fault in that the two rear tyres take it in turns to flag up alarms. Pressures are checked, and they are fine. Reset it, will be ok for miles, then , ping, off it goes again. Has been back to dealers ( who are fkn useless but that's another story ) who said they couldn't find anything wrong. All this started after I had a puncture on the o/s/r which system did pick up tbf, although tyre was destroyed
..

 

[Love-Cupra]

Mine did tell me which tyre was low both times.

Not sure why each car seems to act different - very strange

Strange indeed, to state the least.
Guess SEAT will just use what is available in the factory, at that given time ?

 

[Mr Pig]

Although the system uses the ABS sensors it's actually more demanding than the ABS system. All the ABS system has to know is when a wheel stops turning. The speed of rotation doesn't matter, it's a go no-go system.

The tyre pressure system needs to know the rotational speed of each wheel. It's using the same proximity sensors and rings but the accuracy of the information needed is much higher. For the system to work it has to react to small differences as that's what you'd see with a partial deflation of a tyre. Car tyres are designed to hold their shape and it takes more than a few PSI to significantly alter the diameter of the tyre.

If the sensors are not positioned correctly or there is a difference in resistance in the cables for example, the ECU could see a difference in the signal that it could interpret as a difference in rotational speed.

Perhaps some of you have seen old ABS rings that are very rusted? They can be so rusted it's hard to tell what is tooth and what is gap, but they still work. They work for the ABS system that is! If you think these tyre pressure monitors can be flaky now, just wait until a bit of corrosion sets in...

 

[garybuttle]

The TPM also has to allow for the difference in wheel speed when turning a corner or on a roundabout.

 

[Mr Pig]

The TPM also has to allow for the difference in wheel speed when turning a corner or on a roundabout.

Yeah, I wonder how it does that. I had assumed it would simply wait until a difference had been present for a set length of time but you'd want it to flag up punctures quickly. A long bend might exceed what you'd consider a to be a safe warning time.

Perhaps it works on front-to-back pairs, not left-right?

 

[FRTSIman]

About 2 weeks ago the TPMS on my 2013 Leon correctly detected a slow puncture and displayed the correct tyre (front left hand tyre low pressure). When I checked with a tyre gauge, I found that the front left hand tyre was down by 4psi at 28psi from the correct pressure of 32psi in the front right hand tyre. This was the first ever puncture I've had since the car was new, and the first time ever the TPMS has displayed an alert, so I was quite impressed with how well the system worked, especially as the loss of 4psi was not obvious by just looking at the tyres (standard 17 inch tyres on a 1.8TSi petrol Leon FR) and did not seem to affect the steering, brakes or handling. I also checked the back tyres, and these were both on the correct 29psi pressure.

 

[Mr Pig]

The fact that modern cars insulate you from the road so much that low tyres can go unnoticed is a problem. My wife destroyed a tyre by driving around all day on it totally flat without noticing. Wouldn't have been so bad but I bought the tyres the previous day!

 

[romster1]

well on my m3 66 plate I got a warning on only the second or third day of ownership and sure enough the left rear as indicated was punctured by a nail so I cant fault it and hopefully I wont see or get any more flats

 

[chrisRibiza]

Does your's actually tell you which tyre has triggered it on the display?

Anytime mine has went off it doesn't seem to say which tyre is the problem.

 

[mrbugle]

my '14 FR 150 had a puncture 3 times ( always happened when I got on the M6 to drive to Leeds) and it always stated which tyre had triggered it.

 

[Walone]

Tried a little experiment today, I reduced the pressure in the L/H/R tyre down to 27psi from 32psi and went for a drive, the TPMS did not flag up anything so I reduced the pressure down to 25psi and took a drive, still no warning. Then reduced the pressure to 20psi and after driving about 1/4 mile a warning flagged up saying low pressure L/H/R tyre! I then stopped and reset the TPMS to make it think all the pressures were OK and drove about a mile and the system still thought all was OK.
I went home and pumped the tyre up to 34psi to match the R/H/R (warm tyres), didn't set the TPMS and went for a drive and no warnings showed. I then set the TPMS.
I'm a bit disappointed that I had to lower the pressure by at least 7 to 10 psi before the warning came on.

 

[KXL]

I then stopped and reset the TPMS to make it think all the pressures were OK and drove about a mile and the system still thought all was OK.
I went home and pumped the tyre up to 34psi to match the R/H/R (warm tyres), didn't set the TPMS and went for a drive and no warnings showed. I then set the TPMS.
I'm a bit disappointed that I had to lower the pressure by at least 7 to 10 psi before the warning came on.

in between lowering the temps I'm guessing your car was completely off, eg...engine off, key out? Or it was still running?

 

[Walone]

in between lowering the temps I'm guessing your car was completely off, eg...engine off, key out? Or it was still running?

Yes the key was in my pocket, never leave my key in the ignition when I'm not in it just in case some toe-rag comes along!

 

[rickster665]

mine did this a week after the before sale check when i got it from stone acre had to go back they checked everything but nothing
it was all fine no pressure changers so there reconfigured it and not had the issue since he told me there very very sensitive to los or increases so god knows

thing i don't get if why does it not tell you what frigging wheel it is on these silly things its not like its new tek