Tyre Pressure Monitoring - COLD pressures and agjustsments when HOT

[Sparklyman]

Hi,

Can anybody offer some clarity on the TFT TPMS indications ?

The "setpoint" on the Info screen is the BWW recomended pressures (by default I assume ?)

These are 2.5 Bar front and 2.9 Rear - COLD

After 65 miles of riding, the display was indicating both front & rear were above setpoint - this is as expected (as they're now HOT)

Should the COLD pressures be dropped, so the HOT pressures align with setpoint ?

Can anybody confirm this, or offer explanation as what should be done ?

The manual seems to imply the excess (or insufficent) pressures should be adjusted out, so setpoint is achieved when riding (HOT) ?

Manual refers to the TPMS actual pressure as compensated for a nominal 20 Deg C and moves on to using an example of an uncompensated forecourt gauge to adjust for the indicated discrepancies

Just a bit foggy on this, as I've always set COLD pressures, aware that HOT pressures will naturally be higher, but that higher pressure is the target "running" pressure

?

 

[hawkeye]

I always thought that tyre pressure shown were the cold tyre pressures - happy to be corrected (as if so I've been checking my tires incorrectly for years)

 

[Pablo1]

wouldnt concern yourself with the tpms display, get a decent gauge and set pressures cold

 

[MIKE R]

It is very confusing

As I understand it when you inflate the tyres the bike's brain will adjust the pressures shown on the TFT to indicate what the pressure would be at 20c

I spoke to my dealer mechanics about this and did not get a satisfactory reply. I think he was equally confused!

I now simply inflate the tyres when cold to the pressure I want and then check the pressures on the TFT screen immediately I start riding. As the TFT has compensated for 20c the pressures are are normally shown as being slightly higher. As long as these TFT reported pressures remain constant I am quite happy that my pressures are OK

Interestingly on another bike I have aftermarket TPMs fitted to the valve stems. These will show the pressure I inflated my tyres to at the beginning of a ride but can rise by as much as 8psi when riding and the tyres heat up. Obviously same principle as above

Life was so much easier when we relied on simple, often inaccurate tyre pressure gauges!

Mike

 

[leadfarmer]

Set your tyres to the correct pressures cold

On my GS the TPMS gives the same reading as 2 different pumps and a compressor that I have, so either they’re all accurate or they’re all wrong by the same amount

Don’t worry if the readings change when they’re hot, it’s normal, just worry if they drop rapidly, ‘cos you’ve got a puncture

 

[Lord Snooty]

I've turned off the TPS sensor on my 1250GS, it is an unnecessary pain in arse, just another electronic interference that is surplus to requirements, I've never needed it on a bike previoulsy and don't need it now, if I lose pressure in a tyre I will feel it in the handling. The pressures will fluctuate with road heat and external temperature so the TPS will be triggering all the time and all it does is give you anxiety with a stupid message obscuring the TFT screen.

 

[leadfarmer]

Horses for courses, I haven’t got TFT but on the LCD display I have either the temperature or the tyre pressures all the time, I like it

 

[wildbeeste]

I've turned off the TPS sensor on my 1250GS, it is an unnecessary pain in arse, just another electronic interference that is surplus to requirements, I've never needed it on a bike previoulsy and don't need it now, if I lose pressure in a tyre I will feel it in the handling. The pressures will fluctuate with road heat and external temperature so the TPS will be triggering all the time and all it does is give you anxiety with a stupid message obscuring the TFT screen.

On a hire bike (1200GS) in Spain I got a slow puncture but could not tell from the handling until it had lost several pounds of air. The early warning gave me time to carefully get to a petrol station (ten miles) where I could repair it wi the kit and use their airline to reinflate. It is safety issue. The TPS did not give any warning until there was a problem

 

[Deleted account 250319001]

The pressures will fluctuate with road heat and external temperature so the TPS will be triggering all the time and all it does is give you anxiety with a stupid message obscuring the TFT screen.

Once in 7 years my TPMS lit up, And that was after being laid up for several months
Because it had warned me, I went a pumped them up

 

[autogs]

I've turned off the TPS sensor on my 1250GS, it is an unnecessary pain in arse, just another electronic interference that is surplus to requirements, I've never needed it on a bike previoulsy and don't need it now, if I lose pressure in a tyre I will feel it in the handling. The pressures will fluctuate with road heat and external temperature so the TPS will be triggering all the time and all it does is give you anxiety with a stupid message obscuring the TFT screen.

I'm sorry but that's not true, they Don't trigger all the time when the pressures rise due to heat they have temperature compensation built in to the system, your riders manual explains it

Sent from my SM-A202F using Tapatalk

 

[pbbanks]

Tft + tpms also displays the pressure to add or subtract from your tyre pressure guage reading to make the tyre correct at 20c. So, if it says +0.2 bar and you then put your guage on tyre, ignore the actual reading itself but change the pressure in the tyre so your guage shows 0.2bar higher than it first showed. Your guage doesnt correct for the tyre temperature but the tpms does.

 

[RedRick Esq.]

Tyre pressures should be measured cold

The definition of cold I believe from tyre manufacturers is 20ºC

So if done at 15º they will go over pressure for TPMS when the tyres warm up

That is how I understand it anyway

 

[Alan R]

Wow! This could be an interesting and long running thread. So far in dozen or so posts there has been several interpretations of what the display means, what it’s trying to tell you about tft pressure compensated by ambient temperature and the merits of puncture detection by arse gauge or electronic monitoring.
My two penn’orth - check pressures with the same reliable gauge. Don’t worry too much about ambient temperature when doing so as long as there isn’t frost on the ground or the pavement is cracking with the heat. Use the tft readout as a puncture warning feature and don’t fret when the pressure goes up as the tyres warm up.
Alan R

 

[pbbanks]

"don’t fret when the pressure goes up as the tyres warm up."
Thats the benefit of the tpms, it's supposed to compensate for temperature, so, the displayed pressure on tft shouldn't change as the temperature of the tyres increase.

 

[BigT]

The riders manual may be helpful (Page 168 in mine):

Temperature compensation

Tyre pressure is a temperature sensitive variable: pressure increases as tyre-air temperature rises and decreases as tyre-air temperature drops. Tyre-air temperature depends on ambient temperature as well as on the style of riding and the duration of the ride. The tyre pressures are shown in the TFT display as temperature compensated and always refer to the following tyre air temperature of 20oC

The air lines available to the public in petrol stations and motorway service areas have gauges that do not compensate for temperature; the reading shown by a gauge of this nature is the temperature dependent tyre-air pressure. As a result, the values displayed there usually do not correspond to the values displayed in the TFT display.

Pressure adaptation

Compare the RDC value on the TFT display with the value in the table on the back cover of the Rider's Manual. Then use the air-line gauge at a service station to compensate for the difference between the RDC reading and the value in the table.

IMHO the RDC system is best described as a puncture early warning system. Its pressure readings are, or they are on my 21 GSA, fairly accurate but not as accurate as a dedicated and 'calibrated' tyre pressure gauge. When touring, rather than using my dedicated gauge which is a bit of a faf, I bring up the RDC after a minute or two just to check the values haven't changed overnight. Thats it for the rest of the day, relying on a warning from the RDC in case of a problem.

As an aside I found the OEM MICHELIN Anakee lost pressure at a fairly steady rate front and rear. My Metzeler Tourance Next's are as tight as a drum. Recommend the tyre by the way.

Hope this helps those who may be interested........;-)

 

[Bem]

"don’t fret when the pressure goes up as the tyres warm up."
Thats the benefit of the tpms, it's supposed to compensate for temperature, so, the displayed pressure on tft shouldn't change as the temperature of the tyres increase.

Ah yes, but no, but....
My experience is that the indicated pressure will fluctuate during the day, influenced by ambient temperature and use.
It will only flash a warning if there is a sudden change in pressure.
I just check before use with a manual gauge as 28/ 32 and off I go.
( for the benefit of the "quick to respond without thinking" brigade, this is something of a parody, in the style, but not as clever as, Wapping).
I actually am using 32/36 for pottering about.

 

[Alan R]

"don’t fret when the pressure goes up as the tyres warm up."
Thats the benefit of the tpms, it's supposed to compensate for temperature, so, the displayed pressure on tft shouldn't change as the temperature of the tyres increase.

And yet the pressure does rise as the tyres warm up. How can it not when the heat is localized to the air in the tyre? I think you’ve confused ambient ie atmospheric air temperature around the bike with the internal temperature of the air inside the tyre. BMW’s confusingly worded script in the manual tries to deal with the difference between what you see on the tft with what is displayed on a garage air pressure system. A measurement is only as accurate as it’s comparator: the garage system compares its pressure with the outside atmosphere without regard to the ambient temperature whereas the bike can add a calculation for temperature and by extension ambient pressure because it is monitoring that with a temperature gauge. It’s all rather esoteric and of little practical value unless riding up Everest or down a 5 mile deep mine.
Alan R

 

[pbbanks]

The sensors in the tyre also measure the temperature in the tyre ---- quote from net re TPMS--- "A direct type pressure monitoring system uses sensors located in each tyre that are able to monitor the actual pressure levels. The sensors used in TPMS can also provide tyre temperature readings. This monitoring system is able to send all the collected data to a central control module."
So I assume that the bmw bike ones also measure the temperautre. If they don't they should for the price of them , (over £70 each I believe!) .
Yes, the pressure in the tyre will still rise with temperature but the system adjusts that displayed on the TFT to cater for this so it displays what it would be IF the temperarure was 20c. That's why setting them to the tpms recommendations should in theory be better than setting them to a manual (non temp adjusted ) guage.

 

[Wobbly65]

You check tyre pressures before riding with a gauge of your choice. Set them to 2.5/2.9 then ride your bike and forget about it. The tpms will keep an eye on it for you, just forget about it until your next check with your gauge. No need to over-complicate it.

 

[ChazzyB]

On a hire bike (1200GS) in Spain I got a slow puncture but could not tell from the handling until it had lost several pounds of air. The early warning gave me time to carefully get to a petrol station (ten miles) where I could repair it wi the kit and use their airline to reinflate. It is safety issue. The TPS did not give any warning until there was a problem

Agreed. In my somewhat extensive experience with punctures on the GS, the TPMS would always warn me long before I felt any problems with the handling.