
BMW i3 Tire
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.
*Editor's Note: This post from Chuck Vossler, along with an extensive image gallery, appear on BMWBLOG. Check it all out here.

BMW i3 Tire
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: BMW seems to offer a sealant and a compressor included in the frunk.
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.

BMW i3 TPMS Readout

BMW i3 TPMS Readout
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.

BMW i3 Tire
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.

BMW TPMS
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.

BMW TPMS
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.

TPMS Sensors

TPMS Sensors Installed
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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