TPMS registers 2 psi low - Page 2 - BMW K1600 Forum : BMW K1600 GT and GTL Forums
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post #11 of 33 Old 08-06-2019, 03:06 AM
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Originally Posted by Rider59 View Post
It was explained to me that the readout is always displayed at pressure adjusted for 68F (ie: 20C). This would explain some or all of the delta between display and gauge.
Quite.

Unless there’s a delta twixt display and gauge at 20c, I’d be inclined to rely on the onboard TPMS.

I'm just back to the UK after a trip around Spain and ambient temps varied from 18c when I set off from home to 38c while in Spain and the TPMS registered 2.8bar front and rear regardless. Without compensation for temperature, the measured pressure would have varied by up to 4psi across that temperature delta.

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post #12 of 33 Old 08-06-2019, 06:44 AM
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As many have indicated, use a good calibrated tire pressure gauge to check your tires and note the TPS sensor reading. The display is used to watch tire pressure for any problems (My opinion). It does a great job monitoring tire pressure.
I use tire pressure as my display at all times.

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post #13 of 33 Old 08-06-2019, 07:12 AM
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The pressure reading is indeed scaled for temperature. Higher ambient shifts the pressure up. In Florida, checking tires at 80° requires me to put in 45-46 pounds to get the internal sensors to 42.

The fact that both front and rear tires read the same should give you a clue. And if I may ask, what ambient temp was it when you made the readings? Your gauge is accurate, the tp sensors are accurate. Then again, nothing is perfect.

Inflate to an indicated 42 from the bike and ride on!

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post #14 of 33 Old 08-06-2019, 08:23 AM
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Don't use the TPMS gauges to measure pressure. They are not calibrated nor are they designed for accuracy. They are designed to provide telemetry to the bike for relative tire pressure (changes due to temperature/altitude/leaks) readings. My TPMS gauges consistently read about 1.5-2 PSI low (obviously an estimate as they only display whole numbers).

At sea level @ 80f you should be inflating for 43 on a calibrated gauge and the TPMS will say whatever it thinks the pressure is.

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Last edited by earthling; 08-06-2019 at 08:04 PM.
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post #15 of 33 Old 08-06-2019, 01:02 PM
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Same with mine. 2 lbs.under what my good gauges show.
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post #16 of 33 Old 08-08-2019, 03:24 PM
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My 18 GA is off by 1 -2 as well. It is ok as long as you do not see a major drop and that is the point. I am sure that temp has a lot to do with it.
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post #17 of 33 Old 08-08-2019, 04:19 PM
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Quote:
Originally Posted by Rider59 View Post
This is also my understanding, that the TPMS software is always compensating for temperature variances. It was explained to me that the readout is always displayed at pressure adjusted for 68F (ie: 20C). This would explain some or all of the delta between display and gauge.
Thanks -
I also read somewhere that it's set at sea level so different altitudes will also affect the TPMS reading. Mine reads 1 pound low compared to my accurate gauge. I check the TPMS reading every time I ride and ignore the slightly low reading. As others have said, being alerted to a sudden loss in pressure is more important to me than total accuracy.

I think, therefore I ride.

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post #18 of 33 Old 08-09-2019, 11:11 AM
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A BMW service manager adjusted the software or whatever it is to get the TPMS to match his gauge on my '13. I did not ask him to do it, he told me he saw it was off a couple of lbs and set things right. Sadly he doesn't work at the dealership any longer.

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post #19 of 33 Old 08-11-2019, 09:12 AM
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The K16B TPS read out is temperature compensated. Unless your tires are approximately 68F, it won’t matter how accurate or expensive your tire gauge is, the BMW display read out is the air pressure @ 68F. Your expensive tire gauge doesn’t compensate for air temperature.
So if you use your gauge as the pressure indicator, most likely you’ll be riding on under or over inflated tires.

It’s Odd, Confusing, and Counter to what we’ve been doing on all other bikes & equipment, but once you get used to it, it’s easy as the TPS-C display tells you that the tires are properly inflated to 42 psi under all temperatures. Follow the tire pressure adjustment procedure in the owner’s manual to get proper tire inflation for best performance and wear.

Kevin
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post #20 of 33 Old 08-11-2019, 12:46 PM
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Does anyone know if the TPMS has a replaceable battery? My GTL is ~2 years old, and since the last tire change, the front unit readout is intermittent. Comes and goes, sometimes getting an alert if it doesn't read in a certain amount of time. Then it goes away when it re-establishes communication.

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