Tire Pressure Warning
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GLS450
Tire Pressure Warning
Yesterday my TPMS went off. This was my first experience with this. I recalled the left front tire showing 20 PSI. I read the manual this morning and it recommended settings between 29-33 PSI based on the inside gas cap recommendations. After resetting TPMS this morning and driving around for 30 mins or so the reading was well within range, 29-33, not any less or more. Why would this alert sound? I'm in NY and the weather was a lot cooler yesterday for the first time in a while. Also, I did not drive the car all week. Could this have anything to do with the alert?
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It appears as if perhaps your reading of the pressure was not corrrect, maybe the sensor had an issue. I would keep my eye on it and if it reoccurrs and the pressure is OK I would have the dealer take a look.
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1953 300 Adenauer, 1971 300 SEL 6.3, 1975 600, 1978 450 6.9
Most likely nothing wrong . The vast majority of people have no clue how TPMS works - or for that matter - how tires work.
By regulation, TPMS sensors must alert at 25% below the set pressure. Accordingly, if the set pressure is 30psi, then the system must alert at about 22 - 23 psi.
Dealers are notorious for not setting tire pressures right. My 3 week old BMW had one tire set to 60 psi and another at 25. Since the dealer reset the system there were no alerts but I had long learned to check pressures myself.
A tire loses about one psi a month and another psi for every 10 degree drop in temps. So, if you set your tires in June when the temps were 90 degrees and it is 60 now,then You'll have lost 3psi for tems and another 3 for time.
The sensors are not a replacement for checking tire pressures periodically.
Set all your tires as recommended on your door jambwhen the tires are cold (driven less than one mile after sitting overnight)
Reset your system
Check pressures in a two days. If OK, then check again in a week.
If the same tire is low again, then you may have a slow leak. Any tire place can check for that.
By regulation, TPMS sensors must alert at 25% below the set pressure. Accordingly, if the set pressure is 30psi, then the system must alert at about 22 - 23 psi.
Dealers are notorious for not setting tire pressures right. My 3 week old BMW had one tire set to 60 psi and another at 25. Since the dealer reset the system there were no alerts but I had long learned to check pressures myself.
A tire loses about one psi a month and another psi for every 10 degree drop in temps. So, if you set your tires in June when the temps were 90 degrees and it is 60 now,then You'll have lost 3psi for tems and another 3 for time.
The sensors are not a replacement for checking tire pressures periodically.
Set all your tires as recommended on your door jambwhen the tires are cold (driven less than one mile after sitting overnight)
Reset your system
Check pressures in a two days. If OK, then check again in a week.
If the same tire is low again, then you may have a slow leak. Any tire place can check for that.
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GLS450
Thanks guys. I'm sure the left from tire showed 20 PSI when the alert sounded (red). After resetting today all was ok.
CEB, I did pickup a gauge today and when checked with the gauge the readings were about 1 psi off from the cars TPMS. I did not check the readings though when the car was cold but will do so tomorrow.
CEB, I did pickup a gauge today and when checked with the gauge the readings were about 1 psi off from the cars TPMS. I did not check the readings though when the car was cold but will do so tomorrow.
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1953 300 Adenauer, 1971 300 SEL 6.3, 1975 600, 1978 450 6.9
Thanks guys. I'm sure the left from tire showed 20 PSI when the alert sounded (red). After resetting today all was ok.
CEB, I did pickup a gauge today and when checked with the gauge the readings were about 1 psi off from the cars TPMS. I did not check the readings though when the car was cold but will do so tomorrow.
CEB, I did pickup a gauge today and when checked with the gauge the readings were about 1 psi off from the cars TPMS. I did not check the readings though when the car was cold but will do so tomorrow.
I also assume that you actually added air to the low tire before you reset the system. Resetting the system without adding air will not fix your problem, it will merely turn the warning light off.
Document the date and pressure over the next month or so. That will give you a good idea if you have a problem tire.
Most inexpensive tire gauges aren't very accurate, but a couple of psi one way or the other don't really matter. You are looking for larger pressure drops. I suspect that your sensors are more accurate than your gauge.
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GLS450
That's just it, I never had a low tire which is why I'm confused as to why this occurred. I did not add air before resetting because the manual gauge did not indicate a low pressure situation.
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It is my understanding that if you fill your tires with nitrogen, as is offered at many tire stores, your tire pressures will not fluctuate with temperature. However, I do not know if nitrogen is accepted by the TPMS. Does anyone know if you can use nitrogen or not?
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One more thing not mentioned...after driving for a few miles your temp tire psi will rise anywhere from 3 to 5 psi. This would explain your readings after "you had dricen around for 30 min).
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It is my understanding that if you fill your tires with nitrogen, as is offered at many tire stores, your tire pressures will not fluctuate with temperature. However, I do not know if nitrogen is accepted by the TPMS. Does anyone know if you can use nitrogen or not?
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GLS450
For what it's worth, I called MBUSA today to get their recommendations. They said to use the setting located inside the gas cap and to take settings when the car is cold or just prior to the first drive for the day. This morning I took a reading and got 27-28 so I'm just a tad below the recommended 32-33 under normal load.
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1953 300 Adenauer, 1971 300 SEL 6.3, 1975 600, 1978 450 6.9
It is my understanding that if you fill your tires with nitrogen, as is offered at many tire stores, your tire pressures will not fluctuate with temperature. However, I do not know if nitrogen is accepted by the TPMS. Does anyone know if you can use nitrogen or not?
In theory, nitrogen would have some advantages, but in actuality all it is is a way for the dealer to inflate their wallets.
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1953 300 Adenauer, 1971 300 SEL 6.3, 1975 600, 1978 450 6.9
Wait, areyou saying that the sensor showed 20psi, but you actually had much more air inyour tires?
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GLS450
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Driving along, and the display went red and showed some issue with rear left tire. I was literally a block from the neighborhood gas station, so I pulled in. There was nothing obviously wrong, and the pressure was ok (don't remember the number, sorry).
The guy at the service station insisted on having me drive back and forth, and he found a screw that had stuck into the tire, with the head sealing the hole. He pulled it out and patched it without even taking the tire off, charged me $5, and sent me on my way.
He explained to me that the system identifies a sudden decrease in pressure, even if it is a small decrease. I bet you have a nail or a screw.
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It is my understanding that if you fill your tires with nitrogen, as is offered at many tire stores, your tire pressures will not fluctuate with temperature. However, I do not know if nitrogen is accepted by the TPMS. Does anyone know if you can use nitrogen or not?
Ever hear of the gas law? If not, google it.
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It is my understanding that if you fill your tires with nitrogen, as is offered at many tire stores, your tire pressures will not fluctuate with temperature. However, I do not know if nitrogen is accepted by the TPMS. Does anyone know if you can use nitrogen or not?
Funny how one knowing that many laws ignores them all when a sales person explains how good his stuff is.
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GLS450
I might have had something similar happen to me, but I don't remember the exact numbers and such.
Driving along, and the display went red and showed some issue with rear left tire. I was literally a block from the neighborhood gas station, so I pulled in. There was nothing obviously wrong, and the pressure was ok (don't remember the number, sorry).
The guy at the service station insisted on having me drive back and forth, and he found a screw that had stuck into the tire, with the head sealing the hole. He pulled it out and patched it without even taking the tire off, charged me $5, and sent me on my way.
He explained to me that the system identifies a sudden decrease in pressure, even if it is a small decrease. I bet you have a nail or a screw.
Driving along, and the display went red and showed some issue with rear left tire. I was literally a block from the neighborhood gas station, so I pulled in. There was nothing obviously wrong, and the pressure was ok (don't remember the number, sorry).
The guy at the service station insisted on having me drive back and forth, and he found a screw that had stuck into the tire, with the head sealing the hole. He pulled it out and patched it without even taking the tire off, charged me $5, and sent me on my way.
He explained to me that the system identifies a sudden decrease in pressure, even if it is a small decrease. I bet you have a nail or a screw.
I might add I sometimes get a slight steering vibration at just below 60mph during a first drive (15-30mins) of the day. I no longer have this problem after setting the right tire pressure.
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1953 300 Adenauer, 1971 300 SEL 6.3, 1975 600, 1978 450 6.9
No screw found. I have been monitoring the pressure the last few days. It has been below the recommended 32psi (front) and 33psi (rear), more like 28psi and 30psi. I went to Mavis Discount Tire this morning. They have a free tire pressure/air pump. You set the psi you want and fill up the tire until the machine beeps. Now I'm set.
I might add I sometimes get a slight steering vibration at just below 60mph during a first drive (15-30mins) of the day. I no longer have this problem after setting the right tire pressure.
I might add I sometimes get a slight steering vibration at just below 60mph during a first drive (15-30mins) of the day. I no longer have this problem after setting the right tire pressure.
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GLS450
Gas station and tire store "free" pumps - especially those with the "set it and forget it" auto shut-off - are notoriously inaccurate. Go to an auto parts store andbuy the best gauge you can find. It'll probably set you back $15 and you'll save that with increased tire life.
