10-29-2007, 10:21 AM
I was told that the TPM works by matching the rotation speed of each wheel against the other wheels. A low tire will spin at a different rate than the other three and trigger the alarm. We had a flat tire alarm on or 2007 X5 after 3 days. It was a false alarm, so after checking the tire pressures all around, we drove around the block to reset the monitor.
Nope. You were told the FTM (flat tire monitor) works that way. The TPM measures actual tire pressures from each tire. With a TPM you can catch a tire before it goes completely flat and without it needing to "rotate" on the road. So, you don't have to use runflats. With a FTM you get the bad news when you've already started to destroy the flat, or at least compromise the integrity of the tire. So for the FTM you need runflats.
The FTM was a compromise used by putting the ABS system to another use through the computer interface. The TPM is an entirely separate system, considered to be far superior (but still having reliability problems as of last year).
In the 6 series the FTM was replaced by the TPM mid-year in MY production (March 1 2006 build?). I don't know if/when the FTM has been replaced by the TPM in other Bimmers, but the feds are requiring TPM over FTM starting soon.
You can tell which system you have by asking your iDrive. The TPM will register each tire separately on the screen, showing it to be green if it is good. The FTM is blind, since it reads only the axles, not individual tires.
Nope. You were told the FTM (flat tire monitor) works that way. The TPM measures actual tire pressures from each tire. With a TPM you can catch a tire before it goes completely flat and without it needing to "rotate" on the road. So, you don't have to use runflats. With a FTM you get the bad news when you've already started to destroy the flat, or at least compromise the integrity of the tire. So for the FTM you need runflats.
The FTM was a compromise used by putting the ABS system to another use through the computer interface. The TPM is an entirely separate system, considered to be far superior (but still having reliability problems as of last year).
In the 6 series the FTM was replaced by the TPM mid-year in MY production (March 1 2006 build?). I don't know if/when the FTM has been replaced by the TPM in other Bimmers, but the feds are requiring TPM over FTM starting soon.
You can tell which system you have by asking your iDrive. The TPM will register each tire separately on the screen, showing it to be green if it is good. The FTM is blind, since it reads only the axles, not individual tires.