Quote:
Originally Posted by myzmak
Yes, as gthal says.
To expand a bit, the Canadian system (sometimes called 'indirect' or 'passive' TPMS does not measure the absolute tire pressure like you see in the cars south of the border (with the fancy display, etc). Rather, all the system does is measure the relative wheel diameters of the 4 tires by measuring the rotational speed of the wheel (i believe it does this via the ABS). If one tire loses pressure, its diameter will be reduced. That means that to go as far, the tire will have to turn over more times (think about how many times you have to roll a 1" disc vs a 10" disc to go 5 feet...) Turning over more times to go the same distance as the rest of the car means that the rotational speed for that one wheel will be increased. Your car will assume that comes from a tire pressure loss and, voila! the light goes on.
Unfortunately, i know ALL about that because on my old 328 xi I had a terrible terrible experience with some summer wheels i bought that, due to poor installation of hard-to-install low profile RFT tires, they were just destroyed and leaked constantly. the 'beep' of the tire pressure system was a constant companion for me one very, very frustrating summer.
The system sometimes gets fooled up here because of cold weather. In really cold weather the tire can lose a bit of pressure or size (cold air is condensed) and the system can go off. Happens all the time to my mom's Ford Escape. She lives in Sask so, like OP (in Edmonton) can get very cold weather.
The original systems were kind of stupid because, as mentioned, it is all based on relative speed. If (somehow) you had an equal loss of pressure in all 4 tires you'd get no warning because, relative to each other, the wheels would still be spinning at the same rate. The new systems apparently can measure a loss in all 4 at once....though i dont know how well it all works.
Once you have corrected the issue, you have to reset the system via the iDrive.
What i've always wondered is why Canadian cars don't get the fancy-schmancy TPMS they get down south. It would be sooooooo much more convenient. Worth the modest cost of the little monitors.....
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Believe you do not want the TPMS!I have 3 sets of wheels & tires for the M4 and with the FTM you do not need to bother with having sensors in every wheel and making sure they communicate with the car every time you do a tire swap!