06-14-2012, 02:24 PM | #2 |
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It shows when the tire pressure goes below a predefined value. So if your tires call for 38 psi and maybe they drop to 32 psi they'll raise an alert. This is especially important with RFT. The RFTs have a much stiffer sidewall and will never really look flat when compared to a flat regular tire.
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06-14-2012, 04:05 PM | #4 |
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The tire pressure monitoring is different in the US than it is in some (most?) other countries. The US uses a Direct Tire Pressure Monitoring System (dTPMS) sensor inside the wheel that detects a change in tire air pressure. You can tell that your X3 has them from the metal valve stems on your wheels. The system needs to be initialized when you add or remove air from your tires, when a tire is replaced, or when you switch to winter or summer wheels.
Other countries use an Indirect TPMS system (iTPMS). Instead of directly measuring air pressure in the tire they measure rotational speed of the wheel. If a tire has lower air pressure then it will be slightly smaller in size, and will rotate at a higher speed. |
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06-14-2012, 04:10 PM | #5 | |
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Quote:
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06-14-2012, 04:46 PM | #6 |
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06-14-2012, 05:48 PM | #7 |
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Yes. X3s that are built for the US market are built with dTPMS, and X3s that are built for the Canadian market, for example, are built with iTPMS. I didn't know about Oz before Brissim's reply, but I did know that much (all?) of Europe uses iTPMS.
Last edited by 02420X3; 06-14-2012 at 10:34 PM.. |
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06-15-2012, 05:22 AM | #8 |
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Important point to remember, I think, is that both systems detect a change in tire pressure. It's not telling you "good" or "bad" necessarily. It's telling you "close to before" or "so much less than before that it could be dangerous". So, setting your tire pressure properly from the beginning and initializing the system (at least for dTPMS) is important for the system to be meaningful. If you initialize the system when your tire pressure is inappropriately low, you won't get a warning from dTPMS.
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06-15-2012, 05:30 AM | #9 |
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Main thing is when the alert does go off inside the cabin to get them checked asap. Could just be a faulty sensor - I had a puncture alert go off on my E90 at 70mph so limped home at 40mph only to find there was nothing wrong with any tyre.
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06-15-2012, 06:41 AM | #10 |
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Keep in mind rapid changes in temperatures can be enough to trigger a low pressure alert, especially if you were right at the threshold. Over the years, our other vehicles with TPMS have sat in a warm garage over night, then after sitting in work parking lot at sub zero temps the alert would be on for the drive home. Often times the alert would be off by the time I made it home due to the tires warming up slightly.
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06-15-2012, 07:44 AM | #11 |
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I live in Europe and I have probably iTPMS. One of my friend with X3 too, from the same country, has a problem with this sistem. It never worked. It is could probably from the i-drive settings, personal settings ? He going back the car to the dealer, at the service, and after few days, the answer was: "we don't know why the iTPMS doesn't work". Maybe the software problem ?
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06-15-2012, 10:40 AM | #12 |
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My guess is the more direct method by using sensors that measure the pressure rather than using a passive system based on tire rotational speed is more due to the fiasco with Ford Explorers and other SUV's in rollover accidents due to low tire pressure. US probably felt that the passive system was not good enough. I'm glad to have a more active system, regardless. If all of your tires are running low, the passive system won't detect that. Rare? Yes. But seasonal changes can be major and create that condition.
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