General topics » Could we discuss TPM theory (according to BMW)?

BMW says the TPM monitoring bases it's readings on a reference ambient temperature of 68 degrees F. They would like to think we're going to check our tire pressures before a ride, get the ambient temperature reading, and correct the air we put in our tires as if the temperature was 68 degrees. So, if it's 48 degrees, and knowing 10 degrees will result in a 1 psi tire pressure reading, the indicated pressure on our tire gauge should read (using the front tire, say, with a "desired" psi of 36) 34 psi, since at 68 degrees it should rise to the "desired" 36 psi. Thus, with 34 psi in our tire before riding, when it's 48 degrees outside, the TPM will "theoretically" read 36 psi, since it "corrects" to the 68 degree reference.

This seems like a lot of extra effort. So it begs the question: Is anyone here actually doing all this mental gymnastic work, or just putting in the desired psi based on your tire gauge and calling it good?

I get the theory, and it's probably sound and would give you correct TPM readings, but I use TPM readings basically to inform me when/if my tire pressure unexpectedly changes during a ride.

Tyre gauge only for me. View TPM as a warning system only.

Inflate to 42/36. If it’s extremely cold and filled when extremely cold, check once things have warmed up. Of course, TPMS indicates over inflation by that point, so it’s just letting out some pressure.

Useful previous thread here (a 'compulsory' forum hyperlink):

Trying to understand TPMS behavior.

I check my tire pressures before each ride when it is cold. After the tires warm up, even on a warm day, the indicated TPM tire pressures are within one PSI of the pressure that I checked when the tires were cold. So apparently somehow the BMW system compensates for warm tires.

Ignore the numbers. Inflate to your choice of pressures before every ride.

As above, only of any use when you get a puncture and Orange lamp turns Red in a few seconds.

All it’s good for.

Zitat von Becksy im Beitrag #2

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Tyre gauge only for me. View TPM as a warning system only.

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My first bike with temperature compensated TPMs was the 2011 K1300S. I wasn't sure what to think about temperature compensation.
Over time I learned to like it for trips.
I look at the chart next to my air compressor when checking the pressure with my gauge before a trip and when we take off I look at the dash reading and remember those numbers. (I don't worry if it's 1 PSI off from what I wanted.) I also ask Debbie over the intercom what her pressures are.
During the trip every day or so I look at the dash TPM readings and if it's within 2 PSI of the first day I leave the pressure alone.
If the temperature in my garage is around 68 F or I compensate to 68 when I air my tires, my gauge is within 1 PSI of the dash reading.
On most trips I can go around two weeks without adding any air to our tires.

I used to have a chart showing temps to 1 degree staring at 68 F and 0.1 PSI but now I round off temps and PSI.
Tire Pressure (1).jpg - Bild entfernt (keine Rechte)

My two optional displays show engine temp and Tyre data.
Provided they are within approximately the same values as I ride then that is close enough.
Temp between 79 to 82, after going up to 93 then drops for a warm setting.
Tyres can be 2.4 to 2.6 front and 2.8 to 30 rear and all is good.
Safety net of Orange or Red warnings working in the background.

I'm not able to feel a 2 PSI change in tires, some riders can.
If I only did day rides it would not matter what method I used if I went for a ride when the temps were between 50F and 90F.

Zitat von Dave H im Beitrag #10

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Safety net of Orange or Red warnings working in the background.

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BTW 68 degrees for cold tire pressure is not just a BMW Motorrad thing.
https://www.rimex.com/blog/top-5-benefit...ation-pressure/

Zitat von Lee im Beitrag #13

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BTW 68 degrees for cold tire pressure is not just a BMW Motorrad thing.
https://www.rimex.com/blog/top-5-benefit...ation-pressure/

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I correct tire pressure to ambient temp cold pressures based on the 68F at 68 [ I call it even at 70F ]. So when heading out for the day in August when the garage is 90, I set to 38/44. When the garage is 50 in Dec. I set them to 34/40.

The tpms shows within 1-2 degrees from what I put in the tires. Like Lee, if I'm on a trip, I check the tpms reading, if they are the same as the day before or off by 1-2 psi, I don't concern myself further