TPM - what is involved

[Randy]

There is much that has written about how the BMW Tire Pressure Monitoring system functions as well as the hardware involved. The facts I have been able to uncover is that the system consists of three items: A sensor (RDC sensor) in the front wheel.
A sensor (RDC sensor) in the rear wheel.
A receiver (RDC control unit) under the seat where the alarm unit is mounted. The control unit can be paired to two wheel transmitters and must be 'registered' using the GT1 (Group Tester 1) diagnostic unit. The control unit must be installed in the ZFE using the GT1. The wheel transmitters are similar to others on the market - they have a lithium power source and are 'excited' into transmission by wheel motion. The units will not transmit tire pressure readings until the bike has been in motion. The display is on the instrument cluster in the same place as other BC readings and may be toggled through with the BC switch. I have not been able to look at the actual wheel sensor to see if there is a clue who BMW sourced the unit from. Since the RDC control unit appears to be combined with the alarm, I am not sure if you can have one without the other. Below are some pictures - I apologize for my face being reflected in the instrument panel picture, it was a quick snap in poor lighting conditions.

Front tire sensor:

http://randy.bmwlt.net/tpm-front.jpg

Item 1 is the sensor, item 2 is the attachment bolt.

http://randy.bmwlt.net/tpm-front1.jpg

Rear tire sensor:

http://randy.bmwlt.net/tpm-rear.jpg

The rear sensor (item 1) is combined with the valve stem and retained by a large external nut.

http://randy.bmwlt.net/tpm-rear1.jpg

Control unit (item number 1):

http://randy.bmwlt.net/tpm-cm.jpg


Display:

http://randy.bmwlt.net/tpm-display.jpg

[Randy]

I found out some more data today. The control unit that sits under the sear comes in two varieties, with or without the alarm system. If you have an alarm the control module will replace it. If not, the control unit mounts in that location. The control unit is manufactured by Schrader. Below are the part numbers, but the pricing data is not in the system yet. There are still plans for a retrofit kit, but it has not been released yet. The numbers below are for the GT cast wheels only.


Item #1 is the sensor 36 23 7 653 494
Item #2 is the attachment pin 36 23 7 653 495

http://randy.bmwlt.net/tpm-front1.jpg

Rear tire sensor:
Item #1 is the sensor 36 23 7 694 420
Item #2 is the attachment nut 36 21 7 694 440


http://randy.bmwlt.net/tpm-rear1.jpg

Control unit (item #2):
65 75 7 705 863 (with alarm)
36 23 7 702 720 (without alarm)

http://randy.bmwlt.net/tpm-cm.jpg

[jpalamaro]

Thanks Randy, but I have a question. The RV industry has had tire pressure monitoring systems for a number of years. There are as best I know, two systems. 1. Is an inside band on the wheel, with battery power and transmitter. The receiving unit usually dash mounted, with the ability to read, currently as many as twelve wheels or more individual wheels, tandem/dual and towed vehicle. Warning lights, etc. abound.

The 2. system of which I beileve is basically aftermarket and am not aware of any top of the line RV mfgers using these. I believe the motorcycle industry has had some false starts with this system. It's the system where the transmitting unit and tire-pressure monitoring is integrated into the valve stem cap. Data is transmitted from this valve stem cap to the receiving unit. Rest similar.

Am I to presume that BMW's system is one of these two systems, or has BMW come up with something new?

Rgds