Tyre Pressure monitor calibration

[Titto]

Hi all.
I have the on board tyre pressure monitor and glance at it now and again when flicking through the menus.

I have today adjusted the pressures front and rear and tested with a calibrated pressure gauge, so im happy they are spot on. However, the on board display is out by a bit. Eg; 2.5bar in the front (tested) is displayed as 2.9bar on the dash. 2.9bar rear (tested) is displayed as 3.1bar. All this is done with cold tyres.

Im just wondering if anyone has any knowledge of whether the on board tyre pressure monitor can be re calibrated etc? And if so, is this a dealer job.?

Obviously I go off the pressure gauge I use but it would be nice for peace of mind to have it more accurate on screen if you get what I mean.

Thanks....

 

[littleredrooster]

I suspect the answer will be "No", but in any case it is my belief that the TPS system is more use as a relative pressure measurement than as an absolute - i.e. it is more useful to warn of deflation than as a direct measurement of tyre pressures; I would never trust anything other than a proper gauge for that.

 

[andylel]

As per manual the on board gauge is temperature adjusted to display the pressure at 20 degrees celcius. This might account for the difference. It did on mine.

 

[Titto]

Brill. Thanks chaps much appreciated, just at work and havent got the book with me. Still worth asking on here though!

 

[iandavid]

Mine under read by 0.2bar. Stealer will fix at next service. But as was said the main purpose is to warn of a puncture/valve leak rather than an absolute measurement.

 

[Wapping]

Brill. Thanks chaps much appreciated, just at work and havent got the book with me. Still worth asking on here though!

Useful tip 317

You can always access the Owners Handbook by visiting the BMW Motorrrad Denmark site, clicking on Service, then Manual, then selecting the manual you wish to view in a PDF format. As it's a PDF document, you can also save it to your smart phone, computer, iPad or tablet for easy and frequent self-help reference.

 

[Titto]

Thanks wapping. Downloaded!

 

[Wapping]

Hoorah!

 

[Beemerman59]

As per manual the on board gauge is temperature adjusted to display the pressure at 20 degrees celcius. This might account for the difference. It did on mine.

I've never understood why BMW do this - its the same on my '08 Hexhead. Surely, you want to know the pressures when cold and at the ambient air temperature be it January or July? In practice all it means is I know my sensors are going to be reading 2-3psi higher than my guage in winter, whereas in summer months they are aligned and bang on with each other. Why adjust the temperature reading to be as if it was 20 degrees when the reality is its only 5 degrees? I read the manual several times and I understand that that's what they do, but there's no explanation of why? Maybe I'm just thick....

 

[Wapping]

BMW worked out that most of their bikes are only ridden when the mercury sits at 20C.

If I had to guess.

 

[nig5]

it`s because tyre pressure should be checked at an ambient temp of 20c, which always make winter tyre pressure checks challenging!

 

[Sooty09]

Typically the manufactures give a range of tyre pressures for motorways, two up with luggage, solo etc and the difference they quote is substantial. I have never met a rider who adjusts the tyre pressure to suit their intended normal road riding,
As stated, its best to use the device as an indication of a problem, not an indicator that all is well.
I had the TPM on my last bike but have not taken the option on my new bike, it was useful but not essential.

 

[iandavid]

Interestingly on my 2013 LC the manual give one set of pressures for all riding conditions - 1 up 2 up luggage etc.

 

[Sooty09]

Just looked at my 2014 manual. You are right 2.5/2.9.
My wifes GS650. is 2.5 solo and 2.9 two up with luggage.

 

[karlp]

I've never understood why BMW do this - its the same on my '08 Hexhead. Surely, you want to know the pressures when cold and at the ambient air temperature be it January or July? In practice all it means is I know my sensors are going to be reading 2-3psi higher than my guage in winter, whereas in summer months they are aligned and bang on with each other. Why adjust the temperature reading to be as if it was 20 degrees when the reality is its only 5 degrees? I read the manual several times and I understand that that's what they do, but there's no explanation of why? Maybe I'm just thick....

They have to revert to a standard unit of measurement otherwise the manual would be full of pressure measurements for different countries.

However 20 degrees centigrade is the NIST standard. - unusual

Most are referenced against STP (standard temp and pressure) which is 273 Kelvin i.e. zero degrees centigrade