Flat tire on BMW i3, TPMS comes to rescue

How-To | December 1st, 2014 by 19
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My first experience with the BMW i3’s TPMS (Tire Pressure Monitoring System) came on Day two of our long term test. And out of all places …

My first experience with the BMW i3’s TPMS (Tire Pressure Monitoring System) came on Day two of our long term test. And out of all places in Kansas City, it happened at a Chick-fil-A drive-thru.

We had taken a ramp of the highway and it felt like we ran over a huge rock even though there wasn’t anything visible on the road. While sitting in the drive-thru line at Chick-fil-A, I wondered what the hell we’d hit. Even though there were no warnings on the dash, I pulled up the iDrive to check on the tires. Sure enough, our passenger rear tire is down 15 psi. Three minutes later, I was down another 5 psi and now the low tire pressure alarm goes off.

Less than 150 miles and I am getting the dreaded flat tire.

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Ironically, I am fascinated at the evolving disaster on my i3 and being a journalist at heart, whipped out my iPhone and started snapping pics. Many owners have posted problems about getting flats on the i3 Facebook Group and it’s just day two and here we go!

Interestingly, BMW chose not to install run-flats on the i3 and doesn’t include a spare or even “fix a flat” onboard i3s. Edit: There is sealant and a compressor included in the frunk of which I will probably never use so I don’t wreck the TPMS in the tire.

However, BMW’s newest TPMS i3 tells me exactly how much pressure I’ve lost and exactly which wheel it is, in a wonderful live read out graphical interface. This is huge leap forward from 2007 BMW’s systems and gives me confidence on how to deal with this flat.

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It’s now 7:30 in the evening on a Saturday, so my dealer is closed. I’ve had the i3 less than 48 hrs and I do not want to flat bed it to the dealer. My mind races as I am grabbing the food from the drive thru window.  There’s a gas station about a quarter mile away where I can put more air in the tire. I feel confident, I can at least try to make it there without destroying a wheel with live read out of the tire pressures. The tire’s going down so fast, I am sure it’s toast, so I don’t worry about damaging it further.

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Worse case scenario, I stop and call BMW.

We reach the gas station and fill the tire up to mid 40s PSI per the iDrive dash. This is sooo cool. I don’t have a tire pressure gauge but we are able to use the readout on the i3 to guide how much air to put in the tire and I over shoot a few PSI. The live read of the Tire Pressure works really quickly on the i3. When you start a trip, the tire pressure monitor does take about a quarter to half a mile of driving to give you the initial pressures. As we’ve not stopped during this fateful  trip, it’s still giving us a live read on the PSI.

Carefully watching the dash, we are able to make the short distance to the house and arrive with just over 20 psi.  I put the rear of the car i3 up on a jack stand and take off the wheel.

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No surprise, the tire is toast and I find a huge bolt sticking out of the rear tire.  It’s so big I can’t even pull it out of the tread. Damn. Day two and I trashed a tire.  I can just see the guy at the finance department who tried to sell me the wheel and tire insurance laughing now. For the first time, I notice these tires are staggered.  The front’s are 155/70/19 and the rear 175/60/19’s.  Only the base i3 has a square set up of non-staggered tires.

Monday comes and I go to the dealer with the wheel and drop it off.  Unfortunately, they don’t stock the tire. At just $148, at least the Bridgestone Ecopia EP600 All-Season tire isn’t expensive. Once the dealer got one, I was back on my way for $211.78 with mount balance and tax.

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TPMS – A History

TPMS – These four letters are a big mystery to most drivers. TPMS stands for Tire Pressure Monitoring System. Automobiles manufactured for the U.S. market, starting September 2007, have been mandated to have them, though some BMWs made them available earlier. TPMS is designed to warn the driver if tire pressure falls below a certain programed pressure appropriate for the car, typically 25% of recommended PSI. BMW uses a sensor inside the wheel that acts as a high frequency battery operated transmitter to a receiver inside the vehicle which then displays the info on the iDrive and dash. 433 MHz is a common frequency used by BMW.

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Older TPMS systems used the ABS to monitor changes in tire pressures by sensing changes in rotation of the tire. Communicating this loss of tire pressure has gone from a simple warning light on the dash, to a more graphical system on the iDrive. Currently BMW has several different types of TPMS depending on your build date. Newer BMWs such as the i3, have the ability to show you the actual tire pressure PSI in the iDrive. The Tire Pressure Monitor Sensor for BMW is an integrated unit built into the base of the valve stem and unfortunately does not have a serviceable battery. This means when the sensor battery dies, you have to replace the whole sealed unit.

Our 2007 BMW X3 3.0 si still has its original sensors which are faithfully transmitting, though I expect them to check out anytime soon now. I think a 4-5 year timeframe seems to be a reasonable life expectancy of the sealed units.

How to install TPMS

BMWBLOG installed a set of TPMS on our HRE FlowForm Wheels and documented the straightforward process. I purchased the set from Tirerack and asked them for directions, only to get a huge pause on the phone because they said “TPMS sensors are so simple that they don’t even come with directions.”  I was compelled to install the TPMS sensors on our HRE Wheels because NTB wanted to charge me a fee for each wheel to install the sensors.

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Each TPMS wheel set comes with a sensor which was in my case was orange, a valve stem with gasket, a locking nut and a small retaining screw with a square head and finally a valve cap. To install, line up the base of the valve stem with the orange sensor and hand tighten retaining screw. Now slip the valve stem through the valve stem hole in the wheel. Next take the large nut and slip it over the top of the valve stem from outside the wheel and cinch it down with a 11 mm deep well socket.  The square head of the small screw locks into place of the orange sensor and obviates the need for a tiny allen wrench. Finally install the valve cap. Done. Piece of cake.

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If you try to order a stand alone set of TPMS sensors off the website from Tirerack, you cannot find them. They want you to call. The reason being that even with in the same year of model of BMW you can find different sensors.BMW uses Huf Hülsbeck und Fürst from Germany. The TPMS set that Tirerack sent me were made by Huf. They were easy to install and once reset/initialized via iDrive, have worked flawlessly on my E92 M3.

OEM TPMS sensors run $85 each but can be found for just under $70/wheel if you search the web a bit.

Ultimately, TPMS has evolved from being a federally mandated idiot light on a dash to a very useful set of information of live read out on your iDrive. Porsche has had live Tire Pressure read out dating back to 2009, and I am glad to see BMW has evolved their TPMS to such a useful monitor and integrated safety system.

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