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TPMS registers 2 psi low

6K views 32 replies 25 participants last post by  StephenV 
#1 ·
FYI. Both F/R TPMS register 2 psi low on 2019 K16B. I own 2 high end digital air gauges that both read to the .1 psi of ea other. (Griots garage and Summit racing). I have noticed that both consistently measure 2psi low. Anyone else notice this?
 
#2 ·
only ever indicative, if that's what your bike reports stick to that. Possible that BMW could apply correction factors to the software
 
#3 ·
I only use mine as a warning indicator to a leak or other issue - I do not rely on them to be as accurate as my digital gages.
 
#4 ·
My 18 B was pretty accurate until i changed tires. Now my back is pretty accurate but my front is 2lbs. Off. My dealer says it's within margin of error.

In my opinion, the bikes air pressure readout is to catch a leak or puncture. I leave the readout on all the time so I'll hopefully catch a leak early should it happen.



Sent from my SM-J327T using Tapatalk
 
#5 ·
Sudden deflation should take priority over other displays. Though it is my preferred display option.
 
#6 ·
I have never had a motorcycle TPMS be 100% accurate. Their job (IMO) is to warn of rapid (over the course of the day) or sudden (puncture) air loss. Mine served its purpose well, with the red triangle warning when I picked up a drywall screw on the slab in the middle of the NV desert (on an Iron Butt ride).

Took less than a minute to lose ALL air pressure, but I was pulled over before it was all gone.

FYI, my current TPMS on my '13 GTL is one pound low.
 
#7 ·
Yes.

Duane
 
#12 ·
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.
 
#13 ·
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!

 
#14 · (Edited)
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.
 
#18 ·
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.
 
#19 ·
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.
 
#20 ·
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.
 
#21 ·
@Immtbiker, some 'say' the battery is replaceable and there's a youtube video showing how to do it, e.g. dig out potty compound, directly solder wires to end of battery, etc. If you're still within the factory warranty the TPMS is covered. Extended warranties also cover the TPMS.

Duane
 
#23 ·
I always check tire pressure before riding and inflate both tires to 42 psi while the tire is cold. With the Bridgstone OEM tires the TPMS would start at around 40-41 and then show temps up to 46 F consistently as the tire warmed up. With the Dunlop RS III's the TPMS is showing 40-41 at the start and then usually stabilizes around 42-43. I dont recall ever seeing it more than 44 F.
Regardless of how accurate the TPMS is showing to be I use it to read relative pressure fluctuations while riding; I use my gauge to adjust inflation pressures when the tire is cold. It seems to consistently work for me.
 
#24 ·
To paraphrase Shakespeare: "This learned constable [i.e., the TMPS system] is too cunning to be understood."

I have the tire pressures up on my display all the time and keep a close eye on them to maybe spot it if one starts to lose air, but I use a good gauge to actually air up my tires.

What seems odd to me about the TPMS is that the pressure that is displayed is supposed to be adjusted to what the pressure would be if the tire was at 68F, which would make sense; but the displayed pressure changes as the tires warm up. I guess I don't understand the adjustment algorithm. The amount of air in the tire doesn't change, it just expands (or tries to expand) as it warms up so the pressure increases; but if the TMPS were adjusting the PSI to what it would be if the tires were at 68F the displayed pressure shouldn't change. Maybe the TPMS doesn't report actual tire temperature, it uses the ambient temperature which is sensed someplace else and the tires are actually warmer than ambient since they are on the pavement and flexing.
 
#25 ·
It is an interesting discussion. I don't know how they could account for all the variables in an algorithm - seems like to me that they are just saying to inflate to 42 psi at sea level and 68 degrees. If you are riding on a hot day or cold day and/or mountain terrain, the PSI will go up/down accordingly but it would be within acceptable limits unless you are in an extreme situation.
 
#26 ·
Fun story:

Before yesterday's ride to test the passenger peg risers I checked and adjusted the pressure in both tires to read eactly 42 PSI (using my El Cheapo tire pressure gauge to measure). When the TPMS came alive a couple hundred feet from the driveway, both tires indicated exactly 42 PSI. I scrolled over to the Temperature display and you'll never guess what was the ambient temperature....

That's right.... 68°F.

Seems the Rider Manual is correct, eh?
>:)
 
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#27 ·
Besides the OEM TPMS does anyone have experience with an aftermarket unit sensor? My 5 year old GTL/Exclusive's TPMS is showing low battery as reported by a dealer and my GS-911. The rear tire is taking a LONG time for it to display so it's apparently due for replacement.
 
#30 ·
Y'all are funny, and maybe even slightly obsessed. :)

I air the tires up when I mount them, then just forget about it unless my TPS throws a sudden low pressure warning.

If I'm running a car tire, the pressure doesn't change significantly enough to matter. And if I'm running motorcycle tires, they don't last long enough to worry about a couple of psi.

Just ride the dämn thing... :k16:
 
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