More TPMS fun & games

[Steve928]

Day 1 of a 5 week trip, 200 miles done.. PING! "Front left tyre low pressure 3.8 bar'.

 

There followed a quick mental calculation, 3.8 * 14 = 54psi i.e. 3 psi higher than the cold pressure it has been set to for over 10,000 miles.

Stopped for fuel a few miles later and checked both front tyre pressures: equal and exactly as expected.

 

So for some as yet unknown reason the TPMS is no longer happy with the left front pressure which is equal to the right front pressure and hasn't caused an alarm in thousands of miles. I can only think that the trigger value in the BSI has somehow become corrupted.

Perhaps it'll all be alright in the morning..

[Derek Uzzell]

Given that Bailey Peugeot Boxer-based motorhomes have ‘camping-car’ tyre as original equipment and that Bailey recommends tyre pressures that are much lower than those advised by Fiat/Al-Ko for Ducato models with an equivalent specification, and that you were able to reduce your motorhome’s recommended tyre pressures by 50% without the TPMS being triggered, it has to be asked a) what pressures your motorhome’s TPMS sensors are set to and b) whether your Bailey’s TPMS has ever functioned correctly.

[Robinhood]

Derek, there is an implication in Steve's previous posts on this subject that his 'van is factory-stickered at 55F/80R for tyre pressures (and that the TPMS sensors have been set at that from scratch).

 

I may be interpreting previous posts wrongly, but this one adds weight to that interpretation.

[Derek Uzzell]

Robinhood

 

I’m aware that the Bailey ‘stickers’ on its motorcaravans advise pressures significantly lower (for front tyres) than those normally advised when camping-car tyres are fitted to Peugeot Boxer-based motorhomes.

 

Bailey orders a cab from Peugeot and this cab then has an Al-Ko chassis grafted on to it with Bailey carrying out the final conversion. As you highlight, the critical question is whether the TPMS sensors in the wheels that end up on Bailey motorhomes and the Bailey motorhomes’ TPMS have been adjusted somewhere along the line to accommodate the lower-than-usual Bailey-recommended inflation pressures.

 

This 2015 thread discusses the issue

 

http://www.caravanclub.co.uk/community/discussions/information,-technical-tips-advice/motorhomes/Tyre-Pressure-Monitoring-Bailey/rt/1094983/?p=0

 

and the final posting (27 March 2016 on the 4th page) suggests that the sensors/TPMS are not (or were not) being adjusted appropriately.

 

It’s something that Bailey OUGHT to be able to answer...

[Steve928]

Apologies for the late reply but we are travelling. For the short time that I had the original Michelin tyres fitted I ran them at 55F 60R and the TPMS was happy with that. It was also happy with the tyre manufacturer's recommendation of 48F 52R that I have used since changing to 225 width C tyres some 18000 miles ago. The TPMS alarm for only the NSF tyre stating 'pressure low 58.5psi' (hot on the motorway) was therefore something of a surprise..

 

All I can add at this point is that the alarm remained on for 1000km at which point it dissapeared and hasn't returned. Perhaps the TPMS has ' re-learned' the correct value and is now happy again..?

 

 

[Derek Uzzell]

Steve

 

As I understand it, your Peugeot Boxer-based Bailey motorhome (with Al-Ko chassis) is fitted with 15” wheels and came as standard with 215/70 R15CP Michelin “Agilis Camping” tyres. These tyres have a design capability to withstand a high inflation pressure and, for a motorhome with that size tyre, Peugeot’s and Al-Ko’s recommendation would be to inflate the tyres to 72.5psi (front wheels) and 80psi (rear wheels).

 

Consequently, when a TPMS system is part of a Boxer/Al-Ko-specification motorhome’s original equipment, it would be logical to expect the in-wheel sensors to be calibrated to reflect the 72.5/80 pressures. However, Bailey chooses to advise a significantly lower front-tyre inflation pressure (55psi?) and - based on on-line motorhome forum comments - the front-wheel TPMS sensors are not recalibrated to reflect that choice.

 

What I find odd about the TPMS fitted to your Bailey motorhome is that (in an earlier thread) you said that you were able to deflate the tyres “...to 50%. of recommended pressure as a test and didn't get a warning.”

 

Now, I don’t know whether that means you were deflating the 72.5/80 pressures to 36/40, or the 55/80 pressures to 28/40, but either way it’s still a helluva pressure reduction.

 

The purpose of TPMS is not just to warn of a puncture (ie. when one tyre is at a much lower pressure than the others) but to also warn when tyre-pressures have fallen ‘naturally’ and reinflation should be carried out to optimise fuel consumption and avoid potential overheating. To allow the latter to happen there must be a lower threshold which, when reached, triggers a TPMS warning. I don’t know what the threshold should be for a Boxer/Ducato, but I would have thought it ought to be significantly higher than 50% of the recommended pressure. If your Boxer’s front-tyre TPMS sensors are calibrated based on a 72.5psi recommended pressure, a warning triggered at 58.5psi would reflect a percentage drop of around 20% (sort of OK perhaps...) but if the sensors are calibrated based on Bailey’s recommendations the warning becomes nonsense.

 

As It’s apparently practicable for a Peugeot dealership to recalibrate a Boxer’s TPMS sensors to the vehicle owner’s tyre-pressure requirements, one would think it should also be possible to ‘read’ the existing threshold figure before it is changed. As things stand Bailey owners don’t seem to know what to expect from the TPMS fitted to their motorhomes and (as far as I’m aware) there has been no guidance from Bailey.

 

 

[Rayjsj]

TPMS systems are a great idea, they keep the drivers informed that all the tyre pressures on their vehicle are within a certain specification, and warns the driver if the pressure falls below that spec.

One of these systems would have saved me a nasty blowout several years ago......BUT, I, the driver owner of the vehicle need and require to be the arbiter of what that spec is, and whose recommendations i follow.

Bailey s recommended spec ? They after all converted the vehicle, fitted the rear Alko chassis, know the weights to be carried if recommendations are followed, know (hopefully) the handling characteristics of the loaded vehicle, so are best placed to set a specification for the TPMS system ? OR Fiats/Peugeots tyre pressure spec ? They know the tyres fitted, when they put it together (tyres last what ? 30,000 miles) but after that ? They know nothing of any constant load above the factory gate weight, or the ride comfort of the final vehicle , which the converter does.

As for the Tyre manufacturers their spec is a very blunt instrument indeed, they just state maximum pressure, NO MATTER what that does to the handling, ride comfort etc., of the final vehicle.

 

Personally i would like a TPMS system, BUT only one with parameters that I can set, with all the data available to me. Otherwise i look on it as a very good safety aid, spoiled by draconian imposistion and legislation. IMO.

 

Pre-legislation systems do that, pre-fitted systems do not.

[Steve928]

As I'm on a flaky mobile signal I don't have the option of reading earlier threads, Derek, but I don't recall saying that I'd reduced my tyre pressures by 50% without triggering the TPMS. Lowering the fronts to 50PSI does ring a bell though. Nevertheless, I've been in the fortunate position to have been able to run my chosen pressures (currently 48F 52R) for 19,000 miles without triggering an alarm, which is why this spurious alarm came out of the blue.

 

Other Bailey owners don't seem to be so lucky with many having TPMS trouble at the pressures stated on the door jamb sticker and with Bailey uninterested and Peugeot dealers in the most part unable to help. While it could have been such a useful system it does appear to have been implemented well before the support network was put in place.

 

Regarding my own case, an alarm appearing after 19000 miles and then disappearing 750 miles later with no change in tyre pressure is worthless. The best course of action is to do as I do; monitor your own tyre pressures and stick insulating tape over the warning light! Fundementally it's a pi$$ poor system I'm afraid yet clearly could have been so much better and a real driver aid.

[Malo37]

TPMS does not measure absolute tyre pressure. It actually compares revolutions turned with the opposite tyre over a certain distance i.e. a tyre with a lower pressure has a slightly smaller diameter so rotates slightly faster. This is picked up and processed by your ABS computer.

 

Therefore the actual tyre pressure in not relevant. What it does tell you is that one tyre is at a lower pressure than the others. Similarly if the other tyres are over-inflated and one is at the correct pressure, TPMS will highlight that one tyre.

 

Tyre manufacturers of course have to mark tyres with the maximum safe inflation pressure. Some van manufacturers (and dealers) specify this maximum tyre pressure as this is the easy and safe option for them to do and does not expose them to errors if for example the van is heavier that intended e.g. overloaded.

The optimum tyre pressure, for handling, comfort and noise is always below the maximum safe inflation pressure. If you can tell them the axle loading, tyre manufacturers will provide the optimum pressures for your van.

[Keithl]

Malo37 - 2016-09-03 8:37 PM

 

TPMS does not measure absolute tyre pressure. It actually compares revolutions turned with the opposite tyre over a certain distance i.e. a tyre with a lower pressure has a slightly smaller diameter so rotates slightly faster. This is picked up and processed by your ABS computer.

 

Malo,

 

That is only one way that TPMS works, it is the 'cheap' way as no hardware is needed. This is called INDIRECT TPMS.

 

The more accurate way of monitoring tyre pressures is to fit a sensor behind the valve in each wheel but this obviously costs more money! This is called DIRECT TPMS.

 

Have a look at this Wiki article... https://en.wikipedia.org/wiki/Tire-pressure_monitoring_system

 

Keith.

[Derek Uzzell]

Steve928 - 2016-09-03 5:20 PM

 

As I'm on a flaky mobile signal I don't have the option of reading earlier threads, Derek, but I don't recall saying that I'd reduced my tyre pressures by 50% without triggering the TPMS....

 

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Tyre-Pressure-Monitoring-Device/37422/

 

Your posting of 19 February 2015 7:10 PM in that thread

 

“...There is no information as to what the pressure parameters are i.e. at what pressure an alarm would be given; I've deflated them to 50%. of recommended pressure as a test and didn't get a warning..."

[Steve928]

Keithl - 2016-09-03 9:23 PM

 

Malo,

 

That is only one way that TPMS works, it is the 'cheap' way as no hardware is needed. This is called INDIRECT TPMS.

 

The more accurate way of monitoring tyre pressures is to fit a sensor behind the valve in each wheel but this obviously costs more money! This is called DIRECT TPMS.

 

Have a look at this Wiki article... https://en.wikipedia.org/wiki/Tire-pressure_monitoring_system

 

Keith.

 

Indeed, Keith. The Sevel bases have Direct TPMS (the Schrader EasyTPMS system) with pressure sensors in the wheel and do report the measured pressure, although you only get to see it if it thinks there is a problem. Clearly, however, it isn't that good at thinking.. A more reliable 'system' would be to walk around your vehicle occasionally and give the tyres a kick.

 

[Steve928]

Another Sevel TPMS wobbly has been thrown. Following the left front false alarm detailed above which eventually cleared itself, we have covered a further 2000 miles through the French Alps and Pyrenees mostly in hot weather without further TPMS incident. Today though, in cooler temperatures we stopped for lunch at 2080 metres at the top of a Spanish col before descending down into mist and rain. At about 800 metres altitude, with the Evian bottle in the driver' s door pocket creaking and collapsing with the reduction in pressure, the TPMS alarm went off; "right front tyre pressue low 53.6psi" which of course is comfortably above the correct pressure that the TPMS has been happy with for the 2600 miles of the trip so far. I can only conclude that it is the reduction in pressure over a short time while descending that has made it give an alarm despite the pressure being correct. And why no alarm for the other 3 tyres which will have been similarly affected? The alarm has stayed on through several restarts at a constant altitude so presumably we are now stuck with it for the next 1000km. Out with the black insulating tape once again.

[Derek Uzzell]

It’s really stating the bleeding obvious, but what you need to do is establish what pressures the tyre-valve sensors on your Bailey motorhome’s wheels are actually calibrated to.

 

As Bailey specifies tyre pressures that differ significantly from those Peugeot and Al-Ko would advise for a motorhome fitted with ‘camping-car’ tyres, either the tyre-valve sensors on a Bailey motorhome will have been recalibrated to reflect Bailey’s specification or they will not have been. In the latter case, assuming that the TPMS system will permit a considerable reduction in pressure (say 20%-30%) from the vehicle manufacturer’s recommended figures, the front-tyre pressures you are using may be right on the pressure-threshold where the TPMS system is designed to begin to issue warnings.

 

If (as seems very likely) Bailey has failed to have the TPMS sensors recalibrated to match their ‘non standard’ tyre-pressure recommendations, it’s a fair bet that the type of odd behavour you’ve described will result.

 

(Have you asked Bailey about this, as they ought to be able to say whether sensor recalibration is carried out?)

[flicka]

Just an out of the box thought.

Not knowing anything about TPMS or how they work.

Are you able to identify what each sensor psi,is set at ?

Is it possible that a rear sensor @ 80psi set could have been put on the NSL wheel. This could explain why the warning comes up at what is the perceived setting ?

i.e. if all wheels were removed at the same time when tyres were changed were they replaced in the same order they came off ?

A simple check (as I see it) would be to swap the NSL sensor with each of the Rears in sequence & see if that deletes the warning.

Alternatively if the sensors can be reset I would assume that the set psi is readable & can be checked.

 

I may be taking out of my a**e, but as I said I don't know how the TPMS work.

[Steve928]

My apologies for the late reply but I decided to put this issue to the back of my mind, enjoy my holiday and deal with it upon my return. Having now returned here's a brief update.

 

First I agree that the first step would be to determine the trigger pressures configured in the system but that has not been straightforward. Bailey should, as Derek suggests, be responsible for setting these values to match the expected tyre pressures and should be able to tell me what they are but that simply isn't the case. That avenue is a well-trodden dead end and you simply get referred to Peugeot. Once you find a Peugeot dealer who is capable of dealing with the TPMS they will happily connect your van to their diagnostics but without evidence of a fault (of which I'd previously had none in 20,000 miles) it would be chargeable work. So easier said than done.

 

As to my 2 alarms being the expected result of running too close to the trigger threshold, well perhaps, but I'm not entirely convinced. Personally I'd struggle to devise an algorythm that would classify 49psi cold as OK but 58psi warm as low, but only after 20,000 miles and for c. 500 miles after which both values become OK again. The second alarm (upon descending) is understandable, even useful, given the rapid drop in tyre pressure that occured, but it should have cleared itself once pressure and temperature stabilised. It didn't but was cleared later by adding 10psi, driving once around an Intermarche carpark and then removing 10psi.

 

However I've now identified a clear fault so the van can be booked into Peugeot for work under warranty. The rear axle TPMS simply does not funtion at all. As Derek reminded me, I'd previously reduced the rear pressures by 50% without provoking an alarm and I've now confirmed that fitting non-TPMS rear wheels also has no effect. I can imagine that a single axle cab unit might be delivered with only its single front axle's TPMS activated, leaving activation and configuration of rear axle(s) to the chassis builder i.e. Al-Ko. Mine being one of the earliest X2/90s (August 2014 build) and thus one of the earliest TPMS-equipped cabs, I can also imagine that perhaps Al-Ko were unaware of this requirement or ill-equipped to perform it and that my chassis unit left them with its rear axle TPMS inactive.

 

We shall see what Peugeot discover and hopefully they will do any necessary reprogramming of the front axles value FOC at the same time. To be continued..

 

 

P.S. Flicka - you can swap wheels about at will as the senders are only reporting pressure (and presumably temperature) and their loaction is determined by proximity to the hub sensors. The only time that the system displays a tyre's PSI is under alarm conditions.

[Derek Uzzell]

You might try asking Al-Ko what (as far as they are concerned) should happen with ‘cab only’ vehicles that have TPMS.

 

This link to an ASOC forum discussion has probably been given before

 

http://www.autosleeper-ownersforum.com/t14872p25-tyre-pressure-monitoring-system-tpms

 

There’s a good deal of piffle, but the postings from “Cymro” seem to suggest that a Peugeot Boxer X290’s TPMS warning pressure-threshold settings can be reset by a Peugeot dealer to an owner’s specification. This MIGHT mean that it’s not possible for a Peugeot dealer to ‘read’ existing settings, but it is possible to reset them, overriding whatever the existing settings are - though that would be pretty odd.

 

I’d want to be badgering Peugeot, Al-Ko, Bailey and Schrader about this, as TPMS is supposed to be a safety-related system but (as far as Boxer X290s are concerned) nobody seems to really understand it.

[Rayjsj]

Steve928 - 2016-09-30 8:18

 

 

P.S. Flicka - you can swap wheels about at will as the senders are only reporting pressure (and presumably temperature) and their loaction is determined by proximity to the hub sensors. The only time that the system displays a tyre's PSI is under alarm conditions.

Another TPMS weakness, surely a program change to the ECU would be able to display the current tyre pressures for the drivers information and re-assurance, only informing when pressure drops below is dumbing down driver responsibility. IMO.

[Derek Uzzell]

Ray

 

My previous Transit-based motorhome had ABS. My current Ducato-based motorhome not only has ABS but also EBD and ESC. I have no way of ‘adjusting’ these safety-related systems - I just assume they will operate effectively when the need arises and, if a fault develops in any of those systems, that I will be warned of this. As a driver I’m out of the ABS/EBD/ESC loop and that’s the way it should be.

 

While it is undoubtedly possible for a factory-fitted TPMS system to provide a readout of the pressure in each of a vehicle’s tyres on a dashboard display and, if a significant pressure-drop is identified, for the display to show a warning (Plenty of examples of this approach on-line) the Peugeot Boxer (and Fiat Ducato) system is not designed to act in that manner. The Peugeot/Fiat system just checks that tyre pressures conform to preset values and only warns if this is not the case at which point information about the specific wheel and pressure is provided.

 

Now, while you might like the Peugeot/Fiat TPMS system to show the pressures in each tyre on a dashboard display and allow a driver to easily reset the pressures that the TPMS system’s software uses, that’s just not practicable. Driver modification of the predetermined TPMS pressure-values is also not included in the system.

 

Me, I’d like to know in detail how the Peugeot/Fiat TPMS system operates and I definitely wouldn’t mind it being possible to have individual tyre pressures displayed on a dashboard readout, but as long as the system works sensibly and is ‘matched’ to the tyre pressures advised by the motorhome manufacturer that should be good enough. It’s the motorhome manufacturer’s responsibility to advise tyre pressures, not a driver’s responsibility to decide that the manufacturer’s advice is wrong and radically alter those pressure data downwards.

 

Steve’s Bailey’s TPMS system either has a fault or has not been set up correctly. Hopefully (as Steve says) the Peugeot dealership that will be dealing with this under warranty will be able to establish what pressures the TPMS is currently using and match them to Bailey’s advised pressures.

[Steve928]

All sorted now, hopefully..

 

Having discussed the matter with my local Peugeot dealership I wasn't confident that I'd escape a charge for programming the system to my own desired pressures that are substantially lower than those on either Peugeot's or Bailey's sticker, or indeed that they would even do this, so I decided to plough my own furrow.

I bought the Citroen Lexia/Peugeot Planet cableset off Ebay and downloaded the Peugeot Diagbox software. At first it wouldn't connect but I realized that I needed an additional £20 converter box for 'Fiat-based' vehicles such as the Bipper and Boxer.

Loaded onto an old Windows XP laptop that has been residing in the loft I'm now up and running and, according to the adverts, "can do everything that a main dealer can do" :-D

 

The rears were disabled as anticipated.

The fronts were programmed to 52psi which is 75% of Peugeot's sticker pressure, so no reprogramming had been done regarding Bailey's stated pressure of 55psi. How I've managed to cover the best part of 22,000 miles with front tyres below 50psi cold is anyone's guess.

 

Now it has been set to 37psi front and 39psi rear, c. 75% of my actual pressures, and there are currently no alarms so hopefully that will be the solution. There are 9 slots in memory for wheel sender IDs which I'm told equates to a set of summer and winter wheels plus a spare for a 4-wheeled vehicle. 6 slots are occupied on mine as I have used 6 different sender-equipped wheels.

 

It's nice to have this diagnostic setup for other purposes too e.g. I can now reset oil counters etc. after my own DIY servicing.