My TPMS is playing up.

[hetty1]

          Hello,

 

                        I was on the local motorway this morning  and the tpms pinged and the the light came on.  It was reporting a loss of pressure on the front left tyre.    There was a lot of traffic and i didnt fancy going on the hard shoulder because of all the traffic.  I  did, though, slow down and came off the motorway to get home.  I   checked the pressure at home and it was spot on.  I  switched off then on again and the light came back on.   I  then checked all 4 tyres and they were all  OK  and I tried inputting the values and the system accepted them as stored. i  then went for a run  and there was no ping and no light.

 

                               So now  I dont know if   the tpms is doing what it says in the title to this  post or whether  I  do have a genuine tyre problem.  I  cant see how the system can be playing up when it didnt flash for a minute then light up; thats what my handbook says the symptoms are when the system is being erratic.  I  am getting the tyre looked at by my independent    just in case  I  have a problem but if  I  havent then the system wasnt working properly this morning.  Surely, if there is a loss of pressure the warning should have reappeared when  I  took the car for a run after checking and storing the pressures? 

 

                          i think there has been a thread on this  before but  I  couldnt find it.    i cant even switch it off before each trip as i  understand it unlike the start stop? Any thoughts?

    

 

[Ootohere]

It does not always mean a pressure drop.  A wheel bearing or sticking caliper can have a tyre getting hot and the warning coming from the TPMS as there is a reading as flagging up a change in circumference.  So with the pressures now set and the TPMS see how it behaves.  And check a wheel / hub is not overheating when you do a longer or faster drive.   When had the TPMS last been reset?

Edited 30 April, 2021 by e-Roottoot

[AGFalco]

14 minutes ago, e-Roottoot said:

A wheel bearing

 

 

Check / correct all tyre pressures and then set the TPMS.

Check all pressures in a week or if the TPMS light comes back on.

Repeat every week and assume you have a problem if one tyre has gone down in pressure.

 

Please note, the car TPMS system does NOT measure your tyre pressures.

 

Thanks, AG Falco

[rum4mo]

In my and other's experience, these TPMS will throw up a false warning once in "a blue moon", once the system has tripped the warning light it will stay on even if that event was false.

 

I think that all you can do is to stop or get off the road ASAP and check all the tyres, if they look and feel okay to a kick, reset the TPMS and continue your journey, if air is escaping the TPMS warning will come back on then you will know that you more than likely have a slow puncture.

 

It is alarming and annoying when that warning goes off, but better having it than not having it I think.

[TerFar]

Tyre pressures should be set when the tyres are cool, not hot after a run. Once you have the correct pressure, reset the TPMS.

 

The TPMS detects the tyre circumference. When you get on the road, the tyres will get hotter, the pressure will go up a small amount, as will the diameter, but well within the tolerance supported by the TPMS.

 

If this happens again, stop as soon as possible and check the temperature of the wheels on that axle and their relative pressures. They should be the similar. If you have a 'dragging' brake or bearing problem, that wheel will feel hotter suggesting a problem making the tyre pressure higher which increases the diameter and triggers the TPMS on that wheel. (My dashboard display tells me which wheel it is.)

[J.R.]

3 hours ago, TerFar said:

Tyre pressures should be set when the tyres are cool, not hot after a run.

 

The TPMS detects the tyre circumference. When you get on the road, the tyres will get hotter, the pressure will go up a small amount, as will the diameter, but well within the tolerance supported by the TPMS.

 

 

The TPMS detects a differing rotational speed between wheels of each axle when driving in a straight line, there is no tolerance in terms of the angular velocity being minutely less at higher temperatures, the tolerance is between the two wheels on the same axle, unless there is a dragging brake etc they will heat up by the same amount.

 

In those terms there is  no problem with resetting the TPMS with hot tyres if all the pressures are correct.

[AGFalco]

5 hours ago, TerFar said:

or bearing problem

'and I have a  slight rumble from a wheel bearing' as reported by the OP on 22 April 21.

 

Thanks, AG Falco

[Ootohere]

When you do track days and check and set tyre pressures cold and check them hot you might well be aware of how much difference the heat in the tyres make to the pressure and that can be between the front tyres.  You might even see the tyres at different pressures before taking to the track.  On track or on the road or like when you fit a spare of different size you can reset the TPMS and stop getting warnings.  You can set wheels / tyres on the same axle at different pressures and set the TPMS to accept these and the. It will be a change from this circumference that triggers a warning 

[J.R.]

Thanks, thats good to know.

 

Tyre pressures do not increase as much as people believe as the unit of temperature used in the combined gas law is degrees Kelvin.

 

A track tyre running over-hot at 100°c would increase the original 2 bar pressure( at 20°c) by less than 8 psi but that would be if the tyre construction was rigid and it could not increase in volume, were that the case then the pneumatic tyre would not have been invented, in practice the tyrewall will bulge and the tread contact point will diminish increasing the rolling radius and it is the latter that could affect the TPMS, on a circuit perhaps where most if not all the bends (on an oval) are in one direction but on the road they usually cancel out.

[Ootohere]

Instead of science I use a digital thermometer and know exactly what the heat gets to on tyres at the track etc.    Plenty threads on the matter over the years.  I know how hot a binding brake can get and how a rim can get hot. Sometimes when you leave a vehicle without TPMS just passing a side of the car can warn you of an issue.     If a TPMS warning happens and it is not in a place where you can stop and check pressures it can be enough to just stop and feel each tyre or have you hand near the hub and see if one is particularly hot.   If nobody ever had issues with warning of pressure loss but worries about random warnings then it is at least giving other issues you have a consideration as to if there are link.     Less than 5psi differences can give warning on some cars and then checking with accurate pressure gauges makes quite a difference from looking at approximates.

Edited 1 May, 2021 by e-Roottoot

[HeavyMetalRich]

A sudden, albeit seeming small drop in the tyre temperature caused by driving through a wet patch of water from a dry road (more likely in the winter) can activate the TPMS warning. The warning is usually for all four tyres in those circumstances though.

[jonboy77]

How about this? If you pull away rapidly and one of the front wheels spin, then the Tpms will throw up a fault.

[Ootohere]

How about you do exactly that time after time after time and you see that does not happen.  

[jonboy77]

17 hours ago, e-Roottoot said:

How about you do exactly that time after time after time and you see that does not happen.  

I have done it and it happened.

 

[Ootohere]

@jonboy77  what did you do, just spin the tyres and get a TC light flash and also get a TPMS light showing even though the tyre pressures were still at the pressures they were at when you set the TPMS? 

[J.R.]

11 hours ago, jonboy77 said:

I have done it and it happened.

 

Once or every time?

 

It should not happen in either case, once would be an indication of problems to come, all the time and there is something wrong.

[jonboy77]

Just the once, I am normally more cautious these days. I believe it to be caused due to the imbalance of tyre rotation speed between each wheel. I may just be deluded though🙂

[Ootohere]

Spinning the tyres under acceleration should not be throwing up TPMS warnings, it is as simple as that.  Yes a wheel might be turning more than the other for a number of revolutions but then that is happening with millions of other drivers and the vehicles do not think a tyre has deflated.

 

[Rich_84]

Mine was playing up & kept telling me a tyre had lost pressure, mine was caused by an ABS sensor that was on it's way out & after it was replaced I haven't had any warnings about loss of pressure!

[HeavyMetalRich]

19 hours ago, Rich_84 said:

Mine was playing up & kept telling me a tyre had lost pressure, mine was caused by an ABS sensor that was on it's way out & after it was replaced I haven't had any warnings about loss of pressure!

 

Interesting, did you have ABS and ESP fault lights on the dash too?

[Rich_84]

2 hours ago, HeavyMetalRich said:

 

Interesting, did you have ABS and ESP fault lights on the dash too?

Yes I did & the engine started revving on it's own, after I had a new sensor & ABS ring fitted all the faults went away.

[AGFalco]

On 16/06/2021 at 01:44, Rich_84 said:

mine was caused by an ABS sensor that was on it's way out

The TPMS system uses the ABS sensors to sense for a tyre pressure problem.

The ESP also takes info from them as well as from other things like the Yaw sensor and Steering angle sensor.

 

Thanks, AG Falco