Jun 24, 2015, 07:36 PM
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Accuracy of In-Dash Tire Pressure Monitor?
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Junior Member
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e350
Accuracy of In-Dash Tire Pressure Monitor?
I wonder if others have experienced a discrepancy between the in-dash tire pressure monitor and actual tire pressures.
I find that the monitor is consistently off by 3-5 PSI even after resetting the monitor several times.
However, it may be that this is within normal operating parameters as the monitor may not be designed to be precise, but to only be a backup/failsafe to accurate manual monitoring.
Would be interested in other opinions.
Thanks.
I find that the monitor is consistently off by 3-5 PSI even after resetting the monitor several times.
However, it may be that this is within normal operating parameters as the monitor may not be designed to be precise, but to only be a backup/failsafe to accurate manual monitoring.
Would be interested in other opinions.
Thanks.
Newbie
Joined: Feb 2011
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E350 Bluetec
Real Close
2011 BlueTec. I've filled the tires to recommendations. Shortly after leaving the garage, 3 are the same as the tire gauge. One is always one pound low. Pressure builds quickly after one mile but the readings are consistent. I think mine is very accurate!
Senior Member
Joined: Jul 2010
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2014 W212 E350 4M
I wonder if others have experienced a discrepancy between the in-dash tire pressure monitor and actual tire pressures.
I find that the monitor is consistently off by 3-5 PSI even after resetting the monitor several times.
However, it may be that this is within normal operating parameters as the monitor may not be designed to be precise, but to only be a backup/failsafe to accurate manual monitoring.
Would be interested in other opinions.
Thanks.
I find that the monitor is consistently off by 3-5 PSI even after resetting the monitor several times.
However, it may be that this is within normal operating parameters as the monitor may not be designed to be precise, but to only be a backup/failsafe to accurate manual monitoring.
Would be interested in other opinions.
Thanks.
Another consideration is the accuracy of your tire gauge. Some of the old style pencil gauges can be questionable. A good dial or digital gauge is an asset. When the TPMS achieves a reading stop the car and compare it to your accurate gauge.
I believe my TPMS is very accurate.
Super Member
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From: Suburban Phila., PA
2012 E350 Coupe
Some additional info:
While the TPMS should provide a reasonably accurate reading of actual tire pressures, it's my understanding that's not its primary function. It exists to warn you of a significant drop in tire pressure - based upon the "normal" tire pressures you have set it for.
If you adjust your tire pressures, you must do a TPMS Reset immediately thereafter. When the tires heat up with driving, the TPMS will then use the Reset values as "normal" to evaluate any significant drop. If you don't do a Reset, the warning system will be inaccurate.
Further, the TPMS system is calibrated to be accurate at sea level. If you live in a high altitude location, the system again may not be accurate.
MB recommends not relying on the TPMS alone for accurate pressure readings. They should be verified with a reliable manual gauge.
As RSIKR notes, many things can affect pressures. I have found that persistent driving with the sun beating down on one side of the car on a hot day raises the pressures on that side in comparison to the other.
While the TPMS should provide a reasonably accurate reading of actual tire pressures, it's my understanding that's not its primary function. It exists to warn you of a significant drop in tire pressure - based upon the "normal" tire pressures you have set it for.
If you adjust your tire pressures, you must do a TPMS Reset immediately thereafter. When the tires heat up with driving, the TPMS will then use the Reset values as "normal" to evaluate any significant drop. If you don't do a Reset, the warning system will be inaccurate.
Further, the TPMS system is calibrated to be accurate at sea level. If you live in a high altitude location, the system again may not be accurate.
MB recommends not relying on the TPMS alone for accurate pressure readings. They should be verified with a reliable manual gauge.
As RSIKR notes, many things can affect pressures. I have found that persistent driving with the sun beating down on one side of the car on a hot day raises the pressures on that side in comparison to the other.
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From: Orange County, Ca
2017 CLA & 2017 GLE350
I checked & reset my Complete TPMS (factory SDS, TPMS tool & certified Tire Pressure Gauge) at sea level & 68 f found 1 PSI off..
If your not using a certified tire pressure gauge you can be off even more..
As previously stated & MB / US law it's for safety not accuracy almost like depending on your outside temperature display for accuracy when it's only to check for frozen temperature & ice..
If your not using a certified tire pressure gauge you can be off even more..
As previously stated & MB / US law it's for safety not accuracy almost like depending on your outside temperature display for accuracy when it's only to check for frozen temperature & ice..
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2014 W212 E350 4M
The TPMS is a great investigative tool. For example you hit the edge of a pothole, concerned about a pressure loss, check the TPMS before the low pressure warning alerts you. The most important factor is consistency. If there is a substantial difference from right to left side after they were inflated to the same pressure I would be concerned. As discussed the pressure increases when you drive and is related to ambient temperature. As BenzMan 369 pointed out, the sunny side of the car on a hot day can be a pound or two higher.
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From: Toronto
MY17 E43 Matte Selenite/Macchiato Beige, MY16 GLE350d Tenorite/Crystal Grey, MY17 B250
The active system (code 475) is mandated in USA and has a wireless pressure sensor in each wheel (as part of the valve stem). This is why you don't see an actual pressure value displayed in the instrument cluster.
Last edited by YYZ-E55; Aug 11, 2011 at 03:45 PM.
Member
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From: Canada
2011 E350 4Matic Estate in Mystic Red
Most Canadian MBs use a passive tire pressure monitoring system (code 477) which uses the wheel speed sensors to determine if a tire is low. The active system (code 475) is mandated in USA and has a wireless sensor in each wheel. This is why you don't see an actual pressure value.
It says that it is monitoring Run Flat tires, but as far as I know, Canadian models are not equipped with Run Flats. Correct?
Also, if I change a tire myself (lets say a flat tire), will I have to go back to the dealer to have the system readjusted? Does it work through a remote wireless sensor in the wheel?
Thanks
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From: Toronto
MY17 E43 Matte Selenite/Macchiato Beige, MY16 GLE350d Tenorite/Crystal Grey, MY17 B250
You do not need to visit the dealer. You can reset the system from the instrument cluster and it will re-calibrate automatically. There is no sensor in the wheel on Canadian models.
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Current: 2011 W212 Previous: 2008 W211 2006 550 2001 Rover 1997 W210
The TPMS is a great investigative tool. For example you hit the edge of a pothole, concerned about a pressure loss, check the TPMS before the low pressure warning alerts you. The most important factor is consistency. If there is a substantial difference from right to left side after they were inflated to the same pressure I would be concerned. As discussed the pressure increases when you drive and is related to ambient temperature. As BenzMan 369 pointed out, the sunny side of the car on a hot day can be a pound or two higher.
Not really sure what other functions might be useful in its place anyways. Need 2 read da manual someday.
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From: Canada
2011 E350 4Matic Estate in Mystic Red
The message when checking the gauge screen states "Run Flat Indicator Active" (the same gauge that shows you the car info and allows you to reset it).
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E550
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e350
FOLLOW UP
OK, so after purchasing a better air pressure gauge, it turns out the the TPMS is very accurate. Those gas station gauges are for s#$t as well, I have learned. From now on I'll trust the MB and my better gauge.
On a different note, just drove ~350 miles on the highway between southern and northern CA and I have to say, driving the E350 really brings a sense of pleasure to driving long distances. Wow.
On a different note, just drove ~350 miles on the highway between southern and northern CA and I have to say, driving the E350 really brings a sense of pleasure to driving long distances. Wow.
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Porsche Macan S SportDesign / Ex M-B's: 11 & 10 & 06 E350's, 02 S500
Indeed, this car is the king of long distances. It's truly an art! I've driven many long distance miles in this baby and I couldn't think of a better car engineered for such drives.
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Porsche 991S, Cayenne S, 1972 BMW 3.0CS E9 Coupe
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Mine is about a pound different from tire gauge I use. Sometimes, some tires will match gauge and a couple won't. Have two gauges and they usually match each other. Interestingly, if leave TPMS on, TP's will change more in some tires than others and then maybe be same for all four again later.
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Porsche Macan S SportDesign / Ex M-B's: 11 & 10 & 06 E350's, 02 S500
This is taking into account safety, comfort, stability, interior ambiance, features, etc., etc.
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Porsche 991S, Cayenne S, 1972 BMW 3.0CS E9 Coupe
Where did I say that it's the only one? Lol. All I'm saying is that this car is engineered for long distance drives, and I can't really think of many that I'd rather be in on said long distance drives. This is taking into account safety, comfort, stability, interior ambiance, features, etc., etc.
This is taking into account safety, comfort, stability, interior ambiance, features, etc., etc.That's better. Sometimes I think you're getting too drunk off the MB KoolAid, so I have to step in to keep you in line once in a while.
