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      09-05-2011, 09:46 PM   #34
Lotus7
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Quote:
Originally Posted by tuco44 View Post
Yep, I do, and I suspect all Cdn X3s do. Of the last three BMWs I have had, only the 2009 E90 M3 had the alloy valve stems. Cdn and US specs often differ.
Amazing!
It's hard to believe that BMW would have to support (2) different tire pressure monitoring systems. Maybe the differing legally mandated system specs result in the need for differing ways to do it. At least you don't have to worry about adding the transmitters to aftermarket wheels, replacing batteries, and it also opens up the option of using tire sealers in leaking tires without destroying the TPMS transmitter.

I'd be very interested in knowing how much pressure loss is needed in a wheel speed sensing system when running run-flat tires. Apparently the thick sidewalls don't deflect very much so the wheel speed does not change very much when the tire looses air. That should make it somewhat more difficult to detect a tire going down. The direct pressure measuring system (with TPMS transmitters) is apparently programmed to signal a low tire warning when the pressure drops 3 psi.