Tire Pressure Monitor

[BlueZ4AZ]

Have you gotten a warning for low tire pressure, and if so how far below the set pressure was it before it warned you?

Mine has never given me a warning, even if I am 10%-15% below the pressure I set in the system.

(I always reset the system properly after filling the tires with air)

[alex2364]

I got a warning few days ago on my rear tire. I had it set at 42 psi and the warning came on at 34 psi.

[BlueZ4AZ]

The thought is...What good is the system if the tires need to lose that much air before a warning comes on?
The lowest my rear tires have gotten while set at 42 PSI, is 36.5 PSI, and no warning has ever come on at that reading.

[6MT4me]

There is a fallacy about the BMW TPM as compared to say the GM Corvette's system which actually gives a a reading of the exact pressure.
Our german system is really for a warning rather than exacting pressures and needs a significant reductionin pressure to warn, and if all 4 tires loose pressure, say as a cold front comes through, well, good luck.
This system does not let you off the hook for monitoring air pressure in your fairly expensive tires! I check my M3's and my Z4's once a week like clockwork, to stay on top of pressures and to help maintain decent tire wear. Got 19000 miles on my original Michelins on the M3 and my Z4 now has Conti DW's (not DWS).
Oh, and Nitrofill or equivalent does hold slightly better but is really more a lateral move than much of an improvement and makes you at the mercy of the tire store for topping off even though in a pinch you can use compressed air.......

[bmwmick]

Originally Posted by BlueZ4AZ

The thought is...What good is the system if the tires need to lose that much air before a warning comes on?
The lowest my rear tires have gotten while set at 42 PSI, is 36.5 PSI, and no warning has ever come on at that reading.

Blue,
Our TPMS only measures the DIFFERENCE in the rolling diameter so if all
4 tires lose pressure, you'll never get an alarm. This is a much cheaper system than the direct pressure readouts. My bike has the direct readout and the batteries are supposed to be good for 3 years, at that point, the sensor need to be replaced. I plan to replace the batteries once I'm out of warranty in another 5 years.

[bjarne]

Originally Posted by bmwmick

Blue,
Our TPMS only measures the DIFFERENCE in the rolling diameter so if all
4 tires lose pressure, you'll never get an alarm. This is a much cheaper system than the direct pressure readouts. My bike has the direct readout and the batteries are supposed to be good for 3 years, at that point, the sensor need to be replaced. I plan to replace the batteries once I'm out of warranty in another 5 years.

That is not correct, at least for my 2011 35is, there is a sensor in each wheel. WHen I first had my Z delivered I had a TPMS failure that could not be reset, and they had to change the controller and the sensor in the right front wheel. The feature has an * in the owners manual (page 83) so it is possible that not all E89s have it.

[bmwmick]

Originally Posted by bjarne

That is not correct, at least for my 2011 35is, there is a sensor in each wheel.

You may be correct: http://www.realoem.com/bmw/showparts...53&hg=36&fg=15 Looks like it may be optional in Canada but mandatory in the USA. I thought all BMW's had the passive TPMS because most of the active TPMS can measure the actual pressure and not just detect a low tire.

[HpDellNestle]

Correct me if I am wrong. I think BMW's system is gear more toward RFT. It is hard to tell a RFT was punctured and lost its air, therefore it is very likely the driver will drive a punctured RFT with essentially no air pressure at high speed which can cause a blowout. I have my warning light came up when one of my tire had an inch long wire stick into it.