TPMS is rather useless

MZWIE · 11-19-2008, 07:10 AM

TPMS only measures the difference in PSI between the tires. If all tires are at say 30 PSI then TPMS thinks everything is OK.

What is needed is the ability to set a value, say 36 PSI and have TPMS tell you when any of the tires is more than 2 PSI low. (Alarm at <= 34 PSI)

ModlessG · 11-19-2008, 07:23 AM

My Grand Cherokee shows the pressure in each tire. So it can be done

Guildenstern · 11-19-2008, 09:29 AM

When it got cold all 4 of my tires lost the same amount of pressure and the TPMS went off. The old system used relative rolling resistance to guess a flat. but the TPMS is activly measuring the pressure of each tire. iDrive won't let you see it. but that's a software application problem. We can't all have Multifunction displays designed by Poliphony Digital. But I know you could get a lot more out of the iDrive then they let you.

You do however kinda get to set the TPMS. Put the tires at the pressure you want, then reset the TPMS. When any of them gets I think 4 PSI low it goes off.

nobbyv · 11-21-2008, 12:34 PM

Quote:

Originally Posted by e34m5

TPMS only measures the difference in PSI between the tires. If all tires are at say 30 PSI then TPMS thinks everything is OK.

What is needed is the ability to set a value, say 36 PSI and have TPMS tell you when any of the tires is more than 2 PSI low. (Alarm at <= 34 PSI)

I noticed this as well. I figured that my dealer would have inflated my tires to the correct pressure, and my TPMS never went off, so I didn't check my pressure for about 5k. When I finally did, I realized I'd been 6 PSI low per tire since new, but never realized it. TPMS didn't realize it either, since it can only detect a relative pressure drop.

clived · 11-21-2008, 12:49 PM

It's designed to spot a puncture, not stand in for essential regular checks and maintanance....

HighQ · 11-21-2008, 12:50 PM

Quote:

Originally Posted by Guildenstern

We can't all have Multifunction displays designed by Poliphony Digital. But I know you could get a lot more out of the iDrive then they let you.

an iDrive hack would be sweeeet

Maine1 · 11-22-2008, 07:50 AM

I would think that the system reset would store the current pressure that each tire is at as the basis to compare against. If the dealer only filled them to 32 and reset the system, the alarm would then only come on at around 28 psi. If the basis pressure setpoint of the system was fixed at 36 psi there would be no need to reset at all.

11-19-2008, 07:10 AM	#1
MZWIE Lieutenant Colonel 388 Rep 1,660 Posts Drives: M2 Join Date: Jun 2007 Location: GEORGIA iTrader: (0)	TPMS is rather useless TPMS only measures the difference in PSI between the tires. If all tires are at say 30 PSI then TPMS thinks everything is OK. What is needed is the ability to set a value, say 36 PSI and have TPMS tell you when any of the tires is more than 2 PSI low. (Alarm at <= 34 PSI)
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11-19-2008, 07:23 AM	#2
ModlessG Private 5 Rep 83 Posts Drives: Join Date: Apr 2008 iTrader: (0)	My Grand Cherokee shows the pressure in each tire. So it can be done
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11-19-2008, 09:29 AM	#3
Guildenstern or Rosencrantz 11 Rep 455 Posts Drives: 2008 Montego Blue 128i Join Date: Apr 2008 Location: Cleveland, OH iTrader: (0) Garage List 2008 128i Coupe [0.00]	When it got cold all 4 of my tires lost the same amount of pressure and the TPMS went off. The old system used relative rolling resistance to guess a flat. but the TPMS is activly measuring the pressure of each tire. iDrive won't let you see it. but that's a software application problem. We can't all have Multifunction displays designed by Poliphony Digital. But I know you could get a lot more out of the iDrive then they let you. You do however kinda get to set the TPMS. Put the tires at the pressure you want, then reset the TPMS. When any of them gets I think 4 PSI low it goes off.
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11-21-2008, 12:49 PM	#5
clived Captain 39 Rep 812 Posts Drives: Evolved 1M Join Date: Feb 2008 Location: UK iTrader: (0)	It's designed to spot a puncture, not stand in for essential regular checks and maintanance.... __________________ 2019+ BSM M2C 2011-2012: VO 1M Coupe, many toys, Evolve Stage 3. 2008-2011: 135i M Sport Le Mans Blue / Lemon / HGSL. Evolve OBD remap - 390bhp. Also in the family: X3 M40d / Audi S4 (V8)
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11-22-2008, 07:50 AM	#7
Maine1 Private First Class 4 Rep 172 Posts Drives: M235xi Join Date: May 2008 Location: Scarborough, Maine iTrader: (0)	I would think that the system reset would store the current pressure that each tire is at as the basis to compare against. If the dealer only filled them to 32 and reset the system, the alarm would then only come on at around 28 psi. If the basis pressure setpoint of the system was fixed at 36 psi there would be no need to reset at all.
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