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BMW X1 (F48) and X2 (F39) Forums General BMW X2 Forum (F39) TPMS

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      12-08-2019, 06:18 PM   #1
c-m
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TPMS

I’m getting some new wheels and tires and I can’t figure out if these cars use the TPMS in the tire or just reset it based on the weight. Does anyone have experience with it?
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      12-08-2019, 08:49 PM   #2
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There is a sensor attached to the interior of each rim, yes. It transmits both pressure and temperature. You can reset the readings in iDrive. It's discussed in the owner's manual.

What do you mean by "reset it based on the weight"?
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      12-09-2019, 06:32 AM   #3
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Quote:
Originally Posted by c-m View Post
just reset it based on the weight. Does anyone have experience with it?
The cars that don't use sensors in the wheels use the rotational speed of the tire compared to the others, it has nothing to do with "weight"
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      12-09-2019, 07:00 AM   #4
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Originally Posted by dianebrat View Post
The cars that don't use sensors in the wheels use the rotational speed of the tire compared to the others, it has nothing to do with "weight"
Gotcha. My old car used to reset it based on the weight of the car somehow and didn’t have sensors in the wheel. Now that you mention it, I do remember the numbers not showing up until you have driven a mile or so. They still have the actual sensor in the wheels though?
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      12-09-2019, 07:57 AM   #5
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Quote:
Originally Posted by c-m View Post
Gotcha. My old car used to reset it based on the weight of the car somehow and didn’t have sensors in the wheel. Now that you mention it, I do remember the numbers not showing up until you have driven a mile or so. They still have the actual sensor in the wheels though?
No, there are no sensors in the wheels on those vehicles, they use the ABS sensors that are already there to provide rotation data to the car, then it does the math and determines if one wheel is rotating at a different speed, it's actually an impressive idea to get around the extra expense of TPMS with sensors, it was not weight, file that one under TIL
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      12-09-2019, 08:04 AM   #6
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Nothing is weighing wheels or anything like that.

There are two systems, TPMS is the pressure (and temperature) monitor, which is an actual sensor in each wheel. The values are displayed directly.

There is an additional system that compares the wheel rotation, using the ABS sensors. These are monitored continuously and the pulses are statistically analyzed to determine whether a wheel is slightly or grossly different from the others, or what it was measured at previously. This is a more severe kind of trigger.

The owner's manual describes them, the first is called "TPM", Tire Pressure Monitor, and the second is called "FTM", Flat Tire Monitor. The same symbol lights up on the dash for both if a bad reading is detected.

Both systems reset in a similar fashion, only while driving. This is mostly because the TPMS sensors don't send signals unless they're rotating. The FTM monitoring, of course, also needs to be moving. In both cases, the road needs to be reasonably straight and smooth, but only somewhat. The statistical averaging takes care of the details.

Recent Volvos do everything with the second system, btw. And they are quite uncanny about it. They don't read out the actual pressure, obviously, but they quickly detect a low tire, and identify it on a diagram.
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      12-09-2019, 08:09 AM   #7
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Quote:
Originally Posted by dianebrat View Post
No, there are no sensors in the wheels on those vehicles
The owner's manual disagrees:

Quote:
General information
Sensors in the tire valves measure the tire inflation
pressure and, depending on the model, the
tire temperature.
and also

Quote:
Use of sealant, for instance from the flat tire kit,
may damage the TPM wheel electronics. In this
case, have the electronics checked and replaced
at the next opportunity.
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      12-09-2019, 08:43 AM   #8
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Originally Posted by //TMT View Post
The owner's manual disagrees:



and also
You totally missed my references to it being the "non-sensor" approach which you actually wound up agreeing with me on
I never said they were BMWs or made assumptions of what their "old car" was.
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      12-09-2019, 09:48 AM   #9
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Quote:
Originally Posted by dianebrat View Post
You totally missed my references to it being the "non-sensor" approach which you actually wound up agreeing with me on
I never said they were BMWs or made assumptions of what their "old car" was.
Yep I guess I did! But actually ours has both
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