False TPMS Alert
Discussion
vikingaero said:
With the current hot weather, the TPMS in the Jazz has been crying wolf everyday.
So every time it goes off, I take my hands off the wheel to make sure it's not pulling from a deflated tyre. Pull over and perform a visual check. Then get the tyre gauge out and tyre pressures should be 33 psi all round, but with the heatwave, the tyres in direct sunlight had increased to 37psi and and 35 psi for the others.
So, in fact it isn't crying wolf, it is actually doing it's job & telling you that there is a difference in tyre pressures.So every time it goes off, I take my hands off the wheel to make sure it's not pulling from a deflated tyre. Pull over and perform a visual check. Then get the tyre gauge out and tyre pressures should be 33 psi all round, but with the heatwave, the tyres in direct sunlight had increased to 37psi and and 35 psi for the others.
TGCOTF-dewey said:
The Honda systems are utterly awful. They're a well known issue. Mine goes off on EVERY long drive.
They're more dangerous than not having one.
Yeah same here with the Mazda.They're more dangerous than not having one.
Most my driving is short local journeys so it is not a big deal.
But if I hit the A roads for over 25 minutes or the motorway, the light usually comes on.
Can be a bit worrying just ignoring it - but suppose the best thing to do is just check the pressures before any long drive ( which is what I do now for peace of mind )
stevieturbo said:
TGCOTF-dewey said:
They're more dangerous than not having one.
A very silly commentIn pretty much every bit of guidance you will find on the design of safety critical systems, frequent false alarms is considered a big no no for very obvious reasons. They actually make the system less safe.
TGCOTF-dewey said:
stevieturbo said:
TGCOTF-dewey said:
They're more dangerous than not having one.
A very silly commentIn pretty much every bit of guidance you will find on the design of safety critical systems, frequent false alarms is considered a big no no for very obvious reasons. They actually make the system less safe.
If the temperature changes beyond its criteria & it tells you so, it isn't a false alarm.
We have a Mazda 2 also & it has never "false alarmed" yet.
I set the pressures every month to the correct cold setting and that is the end of my interaction with it.
Just because there is a system in place to monitor tyre pressures doesn't mean tyre pressures are "fit & forget" with no requirement for general maintenance.
The same is true of all monitoring systems whether on a car or an oil & gas platform in the North Sea, just because they are monitored doesn't mean they are maintenance free.
E-bmw said:
I do get that as I work with control systems etc, however just because the system tells you something is wrong doesn't mean it is a false alarm.
If the temperature changes beyond its criteria & it tells you so, it isn't a false alarm.
We have a Mazda 2 also & it has never "false alarmed" yet.
I set the pressures every month to the correct cold setting and that is the end of my interaction with it.
Just because there is a system in place to monitor tyre pressures doesn't mean tyre pressures are "fit & forget" with no requirement for general maintenance.
The same is true of all monitoring systems whether on a car or an oil & gas platform in the North Sea, just because they are monitored doesn't mean they are maintenance free.
Depends on the perspective. If the temperature changes beyond its criteria & it tells you so, it isn't a false alarm.
We have a Mazda 2 also & it has never "false alarmed" yet.
I set the pressures every month to the correct cold setting and that is the end of my interaction with it.
Just because there is a system in place to monitor tyre pressures doesn't mean tyre pressures are "fit & forget" with no requirement for general maintenance.
The same is true of all monitoring systems whether on a car or an oil & gas platform in the North Sea, just because they are monitored doesn't mean they are maintenance free.
To the user it is a false alarm as the system is telling you there is a problem when there isn't.
To the c&i engineer, it is tripping at the defined trip setting.
A lot of tpms system use wheel speed delta to infer tyre pressure changes as it uses existing sensors and is therefore cheaper to implement as software than actual tp measurement - and is a regulatory requirements in some markets so cars have to have them so is potentially costly.
However, given tyres wear more on the driven axle, this is going to set off the tpms as tyres wear as the calibration on some systems is poor at accounting for wear - as on the Honda system. It's a good example of why using inferred data is not always great idea on safety critical systems.
TGCOTF-dewey said:
E-bmw said:
I do get that as I work with control systems etc, however just because the system tells you something is wrong doesn't mean it is a false alarm.
If the temperature changes beyond its criteria & it tells you so, it isn't a false alarm.
We have a Mazda 2 also & it has never "false alarmed" yet.
I set the pressures every month to the correct cold setting and that is the end of my interaction with it.
Just because there is a system in place to monitor tyre pressures doesn't mean tyre pressures are "fit & forget" with no requirement for general maintenance.
The same is true of all monitoring systems whether on a car or an oil & gas platform in the North Sea, just because they are monitored doesn't mean they are maintenance free.
To the user it is a false alarm as the system is telling you there is a problem when there isn't. If the temperature changes beyond its criteria & it tells you so, it isn't a false alarm.
We have a Mazda 2 also & it has never "false alarmed" yet.
I set the pressures every month to the correct cold setting and that is the end of my interaction with it.
Just because there is a system in place to monitor tyre pressures doesn't mean tyre pressures are "fit & forget" with no requirement for general maintenance.
The same is true of all monitoring systems whether on a car or an oil & gas platform in the North Sea, just because they are monitored doesn't mean they are maintenance free.
TGCOTF-dewey said:
However, given tyres wear more on the driven axle, this is going to set off the tpms as tyres wear as the calibration on some systems is poor at accounting for wear - as on the Honda system. It's a good example of why using inferred data is not always great idea on safety critical systems.
100% agree with that comment about inferred data, especially for alarms.It is a false alarm becuase it's not detecting a pressure drop, it's actually detecting a delta in rolling circumference and inferring that to mean a pressure drop has occurred.
The OED definition of a false alarm is: a warning about a danger that does not happen. In a wheel speed based TPMS system, in the majority of cases when it alarms, you will not measure an actual pressure drop. Hence it is a false alarm.
The OED definition of a false alarm is: a warning about a danger that does not happen. In a wheel speed based TPMS system, in the majority of cases when it alarms, you will not measure an actual pressure drop. Hence it is a false alarm.
TGCOTF-dewey said:
It is a false alarm becuase it's not detecting a pressure drop, it's actually detecting a delta in rolling circumference and inferring that to mean a pressure drop has occurred.
The OED definition of a false alarm is: ?a warning about a danger that does not happen. In a wheel speed based TPMS system, in the majority of cases when it alarms, you will not measure an actual pressure drop. Hence it is a false alarm.
I am still disagreeing with you.The OED definition of a false alarm is: ?a warning about a danger that does not happen. In a wheel speed based TPMS system, in the majority of cases when it alarms, you will not measure an actual pressure drop. Hence it is a false alarm.
I agree that it is using inferred data but that doesn't mean that the alarm is false.
The rotational radius has been calculated/tested to infer that a certain pressure differential will cause a certain speed differential wheel to wheel.
When the (inferred) TPMS system detects that this threshold has been crossed it sets off an alarm to tell the driver that he needs to check his tyre pressures.
That isn't a false alarm, it is an warning that something has changed that could be a tyre deflation issue and should be checked.
MakaveliX said:
Weird thing with mine is...
Long drive on the way there light comes on... Reset light.
On the way back, light doesn't usually come on ?
Maybe it's because my car prefers the drive to a destination and not from
Nothing weird about that, the tyres were warmed up on the way there, the reset recalibrated the system and they hadn't cooled down enough to need another reset on the way home.Long drive on the way there light comes on... Reset light.
On the way back, light doesn't usually come on ?
Maybe it's because my car prefers the drive to a destination and not from
E-bmw said:
I am still disagreeing with you.
I agree that it is using inferred data but that doesn't mean that the alarm is false.
The rotational radius has been calculated/tested to infer that a certain pressure differential will cause a certain speed differential wheel to wheel.
When the (inferred) TPMS system detects that this threshold has been crossed it sets off an alarm to tell the driver that he needs to check his tyre pressures.
That isn't a false alarm, it is an warning that something has changed that could be a tyre deflation issue and should be checked.
Mine goes off EVERY long journey. Every time I've checked the tyre pressure, it's within the manufacturers tolerance. I agree that it is using inferred data but that doesn't mean that the alarm is false.
The rotational radius has been calculated/tested to infer that a certain pressure differential will cause a certain speed differential wheel to wheel.
When the (inferred) TPMS system detects that this threshold has been crossed it sets off an alarm to tell the driver that he needs to check his tyre pressures.
That isn't a false alarm, it is an warning that something has changed that could be a tyre deflation issue and should be checked.
That's a false alarm.
TGCOTF-dewey said:
E-bmw said:
I am still disagreeing with you.
I agree that it is using inferred data but that doesn't mean that the alarm is false.
The rotational radius has been calculated/tested to infer that a certain pressure differential will cause a certain speed differential wheel to wheel.
When the (inferred) TPMS system detects that this threshold has been crossed it sets off an alarm to tell the driver that he needs to check his tyre pressures.
That isn't a false alarm, it is an warning that something has changed that could be a tyre deflation issue and should be checked.
Mine goes off EVERY long journey. Every time I've checked the tyre pressure, it's within the manufacturers tolerance. I agree that it is using inferred data but that doesn't mean that the alarm is false.
The rotational radius has been calculated/tested to infer that a certain pressure differential will cause a certain speed differential wheel to wheel.
When the (inferred) TPMS system detects that this threshold has been crossed it sets off an alarm to tell the driver that he needs to check his tyre pressures.
That isn't a false alarm, it is an warning that something has changed that could be a tyre deflation issue and should be checked.
That's a false alarm.
How are you checking them and to what level of accuracy?
The reason I ask is:-
If you check at the bar pressure (eg 2.2 bar) and check to 0.1 bar that is just under 1.5 psi.
If you check at the psi pressure (eg 32 psi) and check to 0.1 psi that is nearly 15 times more accurate.
For this reason I always use a good digital gauge, always check to 0.1 PSI & I have never ever had a "false alarm".
I did once on a previous car have an alarm that went off on a track day & when the pressures were readjusted it didn't happen again.
E-bmw said:
This may sound REALLY picky/argumentative/pedantic but I assure you it isn't intended that way.
How are you checking them and to what level of accuracy?
The reason I ask is:-
If you check at the bar pressure (eg 2.2 bar) and check to 0.1 bar that is just under 1.5 psi.
If you check at the psi pressure (eg 32 psi) and check to 0.1 psi that is nearly 15 times more accurate.
For this reason I always use a good digital gauge, always check to 0.1 PSI & I have never ever had a "false alarm".
I did once on a previous car have an alarm that went off on a track day & when the pressures were readjusted it didn't happen again.
Digital pressure gauge that is accurate to one decimal. How are you checking them and to what level of accuracy?
The reason I ask is:-
If you check at the bar pressure (eg 2.2 bar) and check to 0.1 bar that is just under 1.5 psi.
If you check at the psi pressure (eg 32 psi) and check to 0.1 psi that is nearly 15 times more accurate.
For this reason I always use a good digital gauge, always check to 0.1 PSI & I have never ever had a "false alarm".
I did once on a previous car have an alarm that went off on a track day & when the pressures were readjusted it didn't happen again.
I can see where you're coming from, and I understand your point. Tyre pressure is extremely important when racing MTB so I'm a tyre pressure nerd. I also used to run a westy track car too, which could overheat its tyres if you were a couple of psi too high - bike engined cars are very sensitive to TP due to their low mass.
The issue is with Honda's system (likely others too given other posts here?). It's overly sensitive to tyre differences x axle and between axle. It's a rolling circumference issue, not one of pressure. There are dozens of threads on the net where people complain about it. To the point where most folks ignore it after a while.
If the TPMS light comes on mid journey wouldn't you just call up the tyre pressures on screen to see what they say? Obviously if they're faulty that's not useful but if you see one is say 3psi down it's just passed the threshold for the warning. If it's a massive drop, you know you need to act more quickly.
ro250 said:
If the TPMS light comes on mid journey wouldn't you just call up the tyre pressures on screen to see what they say? Obviously if they're faulty that's not useful but if you see one is say 3psi down it's just passed the threshold for the warning. If it's a massive drop, you know you need to act more quickly.
That would be a directly measured pressure system. In which case yes. Some regulatory domains require TPMS fitted to all cars. So cheaper cars tend to work using wheel speed delta between and x axle as it uses existing sensors and saves money. These alarm with a light on the dash... No pressure info.
So all you know is that there is a 'problem'. The danger, given the lowest common denominator driver, is they stop somewhere risky and get hit. And typically the false alarms are more likely at motorway speeds.
I've not weighed in to this debate yet for fear of being called a Luddite for my views on whether TPMS is actually necessary or a good thing to have... but here are a few thoughts...
It's a valid point about measuring to n decimal points, especially if like me you strive to be accurate, 32psi is not 32psi unless it's 32.0 (or even 32.00 and so on), it could range from 32.1 to 32.9 ( or even 32.01 to 32.99 ...). It's no different from trying to boil an egg without a seconds display as I frequently remind my wife, '3 minutes' on a digital clock can differ by up to 59 seconds.
HOWEVER, not all TPMS are the same, not all display pressure readings so checking on-the-fly is not always an option. An alert really does infer that you pull over for an actual eyeball. It's probably good that they can't be reset on-the-fly as this would be an irresponsible option eagerly grasped by many.
When you reset the simpler (wheel speed type) you are simply setting those pressures (well, circumferences...) at that point in time, regardless of what they actually are in psi to however many decimal places, so accuracy is sadly totally irrelevant, you could set all tyres wildly different, the system will only alert you to comparative changes from that stored data (which may occur in extremis).
On the semantics of false alarms, I would say that whatever it is technically a capital 'F' capital 'A' False Alarm, a small 'f' small 'a' false alarm is one that causes you unnecessary and unwarranted anxiety... and refer you to Aesop's tale of 'The Boy who Cried Wolf'.
Oh that Sunday mornings were still given to checking oil, water, tyres etc.... don't get me started on 'electronic' dipsticks
It's a valid point about measuring to n decimal points, especially if like me you strive to be accurate, 32psi is not 32psi unless it's 32.0 (or even 32.00 and so on), it could range from 32.1 to 32.9 ( or even 32.01 to 32.99 ...). It's no different from trying to boil an egg without a seconds display as I frequently remind my wife, '3 minutes' on a digital clock can differ by up to 59 seconds.
HOWEVER, not all TPMS are the same, not all display pressure readings so checking on-the-fly is not always an option. An alert really does infer that you pull over for an actual eyeball. It's probably good that they can't be reset on-the-fly as this would be an irresponsible option eagerly grasped by many.
When you reset the simpler (wheel speed type) you are simply setting those pressures (well, circumferences...) at that point in time, regardless of what they actually are in psi to however many decimal places, so accuracy is sadly totally irrelevant, you could set all tyres wildly different, the system will only alert you to comparative changes from that stored data (which may occur in extremis).
On the semantics of false alarms, I would say that whatever it is technically a capital 'F' capital 'A' False Alarm, a small 'f' small 'a' false alarm is one that causes you unnecessary and unwarranted anxiety... and refer you to Aesop's tale of 'The Boy who Cried Wolf'.
Oh that Sunday mornings were still given to checking oil, water, tyres etc.... don't get me started on 'electronic' dipsticks
TGCOTF-dewey said:
ro250 said:
If the TPMS light comes on mid journey wouldn't you just call up the tyre pressures on screen to see what they say? Obviously if they're faulty that's not useful but if you see one is say 3psi down it's just passed the threshold for the warning. If it's a massive drop, you know you need to act more quickly.
That would be a directly measured pressure system. In which case yes. Some regulatory domains require TPMS fitted to all cars. So cheaper cars tend to work using wheel speed delta between and x axle as it uses existing sensors and saves money. These alarm with a light on the dash... No pressure info.
So all you know is that there is a 'problem'. The danger, given the lowest common denominator driver, is they stop somewhere risky and get hit. And typically the false alarms are more likely at motorway speeds.
ro250 said:
Ah, didn't realise that as assumed if it had TPMS you could read the pressures on screen. On thing I've found odd on my 2017 BMW is that when I start the car it tells me I have a low tyre but it won't tell me the pressures until I start driving. If it knows it's low, why doesn't it tell me?!
They don’t measure tyre pressures until the car is moving. The TPMS may be at different locations around each wheel, so the pressures would not be fully representative as a comparison between wheels, until the vehicle is rolling.Gassing Station | Suspension, Brakes & Tyres | Top of Page | What's New | My Stuff