Tire pressure warning.
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Junior Member
Joined: Jan 2002
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Tire pressure warning.
I'm talking about that little yellow circle with the exclamation point that appears on the tach. Page 30 of the Operators Manual. It then refers you to go page 253 of the Operator's Manual.
So I go to page 253 and it says among other things:
Risk of accident and a lot of other dire consequences such as: Stop the vehicle, if necessary change a wheel, check the tire pressure, visit a qualified specialist workshop. So I check the tire pressure and it's just fine. I then go to see a qualified specialist workshop (my Mercedes dealer).
So what do they do? They also check the tire pressure and it's also just fine, even though the little yellow circle with the exclamation point is still on. No problem. They go on the steering wheel and using the on board computer, just turn the little yellow circle with the exclamation point off. So I ask the guy what if a real tire pressure problem crops up? He says don't worry, it'll come on again. (uh?)
I've been driving many, many years and many, many cars without the help of a tire pressure monitor, and all my tires always held up very well because I checked the pressure manually at least once every two months on average. Now I have this tire pressure indicator that will come on even though the tire pressure is perfect. Gime a break!
So I go to page 253 and it says among other things:
Risk of accident and a lot of other dire consequences such as: Stop the vehicle, if necessary change a wheel, check the tire pressure, visit a qualified specialist workshop. So I check the tire pressure and it's just fine. I then go to see a qualified specialist workshop (my Mercedes dealer).
So what do they do? They also check the tire pressure and it's also just fine, even though the little yellow circle with the exclamation point is still on. No problem. They go on the steering wheel and using the on board computer, just turn the little yellow circle with the exclamation point off. So I ask the guy what if a real tire pressure problem crops up? He says don't worry, it'll come on again. (uh?)
I've been driving many, many years and many, many cars without the help of a tire pressure monitor, and all my tires always held up very well because I checked the pressure manually at least once every two months on average. Now I have this tire pressure indicator that will come on even though the tire pressure is perfect. Gime a break!
Member
Joined: Mar 2010
Posts: 119
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From: NorCal
Current: 2019 M5 Donnington Gray, 2021 GLE53 Diamond White Met. Previous: 2010 C63, 2012 E550 Coupe
The tire pressure monitor is set to the current pressure at a certain point in time via the buttons on the steering wheel. If the pressure drops significantly from that pressure then the warning goes off.
It was probably set previously with the pressure too high. Now that the pressure is lower (though actually the correct pressure) the monitor goes off. The dealer simply reset it to your current pressure.
It was probably set previously with the pressure too high. Now that the pressure is lower (though actually the correct pressure) the monitor goes off. The dealer simply reset it to your current pressure.
Member
Joined: Mar 2010
Posts: 119
Likes: 6
From: NorCal
Current: 2019 M5 Donnington Gray, 2021 GLE53 Diamond White Met. Previous: 2010 C63, 2012 E550 Coupe
Yea, sorry about that. I meant the warning goes ON when the pressure drops enough below point it has been set.
Junior Member
Joined: Mar 2012
Posts: 29
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2012 E350 coupe
About a month ago, my tire pressure monitor also came on. Dealer checked all the tires, then reset the limits of the system to 33 psi for the front tires and 34 psi for the back. I found that at those pressures, my car coasted slower, accelerated slower, transmitted more road noise, and got worse gas mileage. After a few days, I went to the gas station and inflated the fronts to 35 and the backs to 37. The car instantly handled like I was used to. Note that these are not cold tire pressures, but rather pressures after some driving.
Member
Joined: Nov 2011
Posts: 116
Likes: 1
From: Manassas Va
2012 E550 Coupe
The primary reason tire pressures increase with temperature is the water vapor in the filling air stream.
The primary reason nitrogen filling of tires results in much less pressure increase is the nitrogen is dry, it has to be to not corrode the tanks it comes in among other reasons.
Since air is about 78% nitrogen, 20% oxygen and the rest trace gases if you are able to fill your tires with dry air, as that found in the air supply for spraying in quality body shops, you could get the same result for free.
When I was actively racing, some of my competitors used an the air drier unit from a heavy duty truck air brake system to fill their tires. The temperature shift relative to using dry nitrogen was neglibible.
The primary reason nitrogen filling of tires results in much less pressure increase is the nitrogen is dry, it has to be to not corrode the tanks it comes in among other reasons.
Since air is about 78% nitrogen, 20% oxygen and the rest trace gases if you are able to fill your tires with dry air, as that found in the air supply for spraying in quality body shops, you could get the same result for free.
When I was actively racing, some of my competitors used an the air drier unit from a heavy duty truck air brake system to fill their tires. The temperature shift relative to using dry nitrogen was neglibible.
