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The Tire Rack's Tire & Wheel Forum
Use this forum to discuss anything in relation to wheels to tires to offsets.
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Old 05-11-2010, 03:23 PM   #1
starlights
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What kind of Tire Pressure Monitoring Sys on 2006 330 Coupe?

I have a Late 06 330 Coupe - I recently changed the wheels and tires from 17" to 18" . The mechanic who did the swap told me that my car does not have TPMS in the tires but the monitoring system runs off indirectly.

Soon after the wheel swap, one of the tires lost all air due to a leaking valve stem while the car was parked - so when I put on the spare (5th wheel of the 17" set) the system inside the car warned me of low pressure in one of the tires - how does it work?
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Old 05-11-2010, 04:03 PM   #2
MeanMangoMan
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Flux Capacitor located in each tire, very intricate tech. Do not mess with it!

Just kidding, as it turns out the 06 had indirect TPMS! Very cool stuff see below:

Having read the manual of the '06 330xi, I see that it uses a so-called "indirect" TPMS which doesn't actually check the pressure, it just detects the difference in rotation among the tires. This system would pick up low pressure in a single tire, but not seasonal pressure changes (due to temperature drops in the fall and winter) that affect all 4 tires. This would explain why many owners had to replace the entire set of tires early.

Another subtle point is that the TPMS had to be "initialized" right after the tires are inflated to the correct pressures, because that's the reference point used by the computer to compare the tire rotation later. If the system is not initialized properly, e.g., not reset after tire rotation or a flat repair, that would also end up running the tires at the wrong pressure.
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Old 05-11-2010, 04:04 PM   #3
howie
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thats pretty much the only place it can monitor...valve stem! Doesn't fit on every rim tho.
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Old 05-11-2010, 04:11 PM   #4
starlights
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Well - we checked the tires, (the 17s which were replaced - and nothing in there) yet when i put a 17in spare with the rest 3 18s - the light came on - my impression is that its got to do something with the rotation of the tire (different rotation on 17 vs the 3 18s) ......... but i could be wrong - and am definitely very confused! Lol
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Old 05-11-2010, 04:36 PM   #5
MeanMangoMan
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Quote:
Originally Posted by starlights View Post
Well - we checked the tires, (the 17s which were replaced - and nothing in there) yet when i put a 17in spare with the rest 3 18s - the light came on - my impression is that its got to do something with the rotation of the tire (different rotation on 17 vs the 3 18s) ......... but i could be wrong - and am definitely very confused! Lol
Did you read my post? It is done by monitoring tire rotation speed.
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Old 05-11-2010, 04:42 PM   #6
howie
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Quote:
Originally Posted by MeanMangoMan View Post
Flux Capacitor located in each tire, very intricate tech. Do not mess with it!

Just kidding, as it turns out the 06 had indirect TPMS! Very cool stuff see below:

Having read the manual of the '06 330xi, I see that it uses a so-called "indirect" TPMS which doesn't actually check the pressure, it just detects the difference in rotation among the tires. This system would pick up low pressure in a single tire, but not seasonal pressure changes (due to temperature drops in the fall and winter) that affect all 4 tires. This would explain why many owners had to replace the entire set of tires early.

Another subtle point is that the TPMS had to be "initialized" right after the tires are inflated to the correct pressures, because that's the reference point used by the computer to compare the tire rotation later. If the system is not initialized properly, e.g., not reset after tire rotation or a flat repair, that would also end up running the tires at the wrong pressure.
NINJA huh...

that's pretty smart. Wouldn't think it was very accurate but wthell
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Old 05-11-2010, 05:10 PM   #7
starlights
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Originally Posted by MeanMangoMan View Post
Did you read my post? It is done by monitoring tire rotation speed.
Yep - reading it now ...... you edited and posted your post after my question
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Old 05-11-2010, 05:13 PM   #8
MeanMangoMan
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NINJA huh...

that's pretty smart. Wouldn't think it was very accurate but wthell
If it works it is pretty low maintenance, nice CLK by the way!
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Old 05-11-2010, 05:52 PM   #9
howie
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Quote:
Originally Posted by MeanMangoMan View Post
If it works it is pretty low maintenance, nice CLK by the way!
thanks, I'm sure it works. But how well does it really work? I mean you would have to be pretty low on tire pressure to notice a difference in rotation...I would think.
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