Tyre Pressure warnings....danger of crying wolf too often

[andruec]

Frankly if I could disable the thing I would do but I gather you have to have these things by law.

Yes. Another EU regulation, in force since November 2014.

Intended to save lives. It would have been introduced by the UK government with or without the EU. Assuming that the UK government cared about its citizens.

[culzean]

Weird as it may seem, it's actually a UN regulation and applies worldwide.

I couldn't find a link to that. Can you post? I got my info here:
https://www.oponeo.co.uk/tyre-article/obligatory-tpms-a-larger-expense-for-owners-of-new-cars

found a bit more,  it was originally UN but had to harmonized (complicated in the usual EU way) into EU law.

https://www.unece.org/fileadmin/DAM/trans/doc/2018/wp29grrf/GRRF-86-17e.pdf

The reason the TPMS can only be reset when car is stopped with handbrake on is to stop people resetting an active alarm on the move.  In USA Honda have a 'reset TPMS' button on the dash,  but I still think car has to have engine stopped and handbrake on (at least they don't have to scroll through menus to do it). 

My wife would not have a clue how to reset the alarm on her car, as I guess 95% of women wouldn't (some may not even know what the symbol that flashes up is trying to tell them).

[peteo48]

Frankly if I could disable the thing I would do but I gather you have to have these things by law.

Yes. Another EU regulation, in force since November 2014.

Intended to save lives. It would have been introduced by the UK government with or without the EU. Assuming that the UK government cared about its citizens.

I think the idea of a pressure warning system is a good one so I have no quibble with the concept. They do need to be reliable though because false alarms totally negate the purpose of the feature. The next time mine goes off I will be assuming it's a false alarm  - I'll do the checks but, unless the car's handling is causing concern, I won't make a special effort to stop.

They do seem to be troublesome - not just Honda. Plenty of stuff on all sorts of forums. The frustrating thing seems to be a plethora of stories where people go into the dealership and they can find nothing wrong.

So, on balance, if it were possible, I'd still have the thing disabled.

[ColinB]

... a plethora of stories where people go into the dealership and they can find nothing wrong.

A dealer will be comparing system performance against how it’s designed to work, so if he reports “no fault found”, you have to conclude one of three things:
1. It’s working as designed, but the design (hardware &/or software) is wrong. That seems unlikely to me given the significance of this system for safety, plus it’s basically an add-on to the ABS which also will have been critically reviewed. Not to mention a fair number of people who don’t seem to have the problem.
Or ...
2. It’s not working as designed and the dealer is incompetent if he can’t find the fault. Definitely a possibility, but it does suggest all the dealers are equally incompetent which seems unlikely.
Or ...
3. The system is working correctly and is detecting a genuine asymmetry between the wheels. The asymmetry may only occur in certain conditions, it may or may not be a pressure difference, and if it is it may not be significant enough to worry about or even be detectable using typical DIY tools, but it must be there.

Which of those is the most likely ? Take your pick, but the Honest John queries posted earlier suggest the last one.

[culzean]

I don't think asymmetry between wheels is a problem as long as it is there when system is calibrated, otherwise a car with some nearly bald tyres and some brand new tyres would never achieve calibration.  I don't think every wheel has to be rotating at same exact speed, just if their rotation changes by a certain critical amount from the value the system has stored for it.  I have had TPMS alarm after replacing worn tyres with new ones, so bringing the wheel rotation speed 'more equal than it was when calibrated' actually caused it to alarm. I don't think ABS system is basically flawed, but some tweaks (spectrum analysis for instance to detect if all tyres are under inflated) may have complicated things.

[ColinB]

I don't think asymmetry between wheels is a problem as long as it is there when system is calibrated, otherwise a car with some nearly bald tyres and some brand new tyres would never achieve calibration.  I don't think every wheel has to be rotating at same exact speed, just if their rotation changes by a certain critical amount from the value the system has stored for it.  I have had TPMS alarm after replacing worn tyres with new ones, so bringing the wheel rotation speed 'more equal than it was when calibrated' actually caused it to alarm. I don't think ABS system is basically flawed, but some tweaks (spectrum analysis for instance to detect if all tyres are under inflated) may have complicated things.

OK, maybe loose wording on my part. By "asymmetry" I meant "a difference between wheels that has developed after calibration". So if one wheel has a rotational speed, or pressure, that is outside the differential limits set during calibration, then that is an asymmetry.

My point was that if a system has been checked and proved to be functioning correctly, then an alarm can only indicate a genuine asymmetry somewhere ... because that's what the system is designed to detect. The driver might interpret this as a "false" alarm, but it isn't really ... it's a genuine alarm but may not be significant.

[peteo48]

So, and bear with my lack of engineering knowledge, if an asymmetry is present, it would trigger the alarm. If the system is then recalibrated, the calibration will take account of the asymmetry (as per Culzean's example of bald and new tyres)?

This is interesting. It may be that, on the first recalibration, I didn't ensure all the tyres were completely even - ie both fronts at 33psi and both rears at 32psi. This could have triggered the second "false" (if, indeed it was false) alarm. 200 miles later (give or take) a period of fast driving exaggerates the pressure difference (although surely all tyres would rise in pressure) and triggers "false" alarm number 2.

Given the extreme care I have gone to in order to have the pressures dead right, if it goes off again the system must be faulty?

[Downsizer]

Based on my own experience, and by all accounts, others on this forum, I think the "false" alarms are most common with recently fitted tyres.  I have not had an alarm for well over a year now, and the tyres have covered 22,000 miles.  If I'm right, some asymmetry may arise as the tyres bed in.

[mikebore]

Based on my own experience, and by all accounts, others on this forum, I think the "false" alarms are most common with recently fitted tyres.  I have not had an alarm for well over a year now, and the tyres have covered 22,000 miles.  If I'm right, some asymmetry may arise as the tyres bed in.

This would explain why Deeps and I both had false alarms very early in our ownership and not again.

[ColinS]

Based on my own experience, and by all accounts, others on this forum, I think the "false" alarms are most common with recently fitted tyres.  I have not had an alarm for well over a year now, and the tyres have covered 22,000 miles.  If I'm right, some asymmetry may arise as the tyres bed in.

This would explain why Deeps and I both had false alarms very early in our ownership and not again.

Same happened to me when I first got the car.  And again when I had new front tyres fitted.  So the theory could be sound.

[Skyrider]

Based on my own experience, and by all accounts, others on this forum, I think the "false" alarms are most common with recently fitted tyres.  I have not had an alarm for well over a year now, and the tyres have covered 22,000 miles.  If I'm right, some asymmetry may arise as the tyres bed in.

This would explain why Deeps and I both had false alarms very early in our ownership and not again.

Same happened to me when I first got the car.  And again when I had new front tyres fitted.  So the theory could be sound.

I pick up my new Jazz on Monday, I will let you know!

[ColinB]

Given the extreme care I have gone to in order to have the pressures dead right, if it goes off again the system must be faulty?

Whilst I don't doubt that you have been as careful as you reasonably can be, the fact remains that you are (probably) using a pressure gauge of unknown accuracy. Others have been dismissive of my idea that gauge accuracy might be a factor, but I have yet to see a convincing argument to demonstrate that any individual pressure reading might not be anywhere within the accuracy band of the gauge, and hence that there might be minor undetected differences between wheels.

[culzean]

[ hence that there might be minor undetected differences between wheels.

Minor differences should not trigger the alarm,  especially if those 'minor differences' are present when system is calibrated.

I guess there may be a software update issued for MK3 Jazz TPMS soon,  the systems on our Civic and MK2 are trouble free and do work well (they know the difference when a new tyre is fitted to replace one with 3mm of tread, also when slow punctures present the alarm works with 4 to 5 psi pressure loss).

[Skyrider]

[ hence that there might be minor undetected differences between wheels.

Minor differences should not trigger the alarm,  especially if those 'minor differences' are present when system is calibrated.

I guess there may be a software update issued for MK3 Jazz TPMS soon,  the systems on our Civic and MK2 are trouble free and do work well (they know the difference when a new tyre is fitted to replace one with 3mm of tread, also when slow punctures present the alarm works with 4 to 5 psi pressure loss).

A software update depends on the scale of the problem, a few people having a few false alarms and tens of thousands of Jazzes not causing a problem worth reporting to Honda is not going to bother Honda too much. When Honda's customer service phone lines are getting hundreds of calls a month and the dealers start complaining about  the grief they are getting from customers about problems it might get their attention.

[Jocko]

Whilst I don't doubt that you have been as careful as you reasonably can be, the fact remains that you are (probably) using a pressure gauge of unknown accuracy. Others have been dismissive of my idea that gauge accuracy might be a factor, but I have yet to see a convincing argument to demonstrate that any individual pressure reading might not be anywhere within the accuracy band of the gauge, and hence that there might be minor undetected differences between wheels.

My pressure gauge is guaranteed to be within 2%. At 35 psig than is 0.7 psig. If, as you insist, I set tyre to 35 psig, and it can read 34.3 for one tyre and 35.7 for another (1.4 psig total difference), and TPMS cannot cope with that variance, then the TPMS system is cr*p and not fit for purpose.
We checked gauges against a large air receiver, far larger capacity than a tyre, and  over a number of measurements the reading was repeatable. And repeatability is more important in manufacturing process control than absolute accuracy.