On my new 2004 S55 the dealership told me that once I drove the car for a little bit the monitor would be more correct or accurate. Every time I get back in the car the numbers are different and their seems to be no solution. Please Help!

 

Remember as the ambient temperature changes so will the tire pressures. Also it doesn't take much driving to push the pressures up 2-3 lbs.

 

Try doing a reset a few times. Also, remember there is astoundingly little air in the tires, so they are very sensitive to changes in temperature. My tires can vary by 5 psi depending on outside temperature and whether the tires are cold or hot.

 

thank you for the reply, I will try that, and you also have a very good point that I had never thought about. The change in temp.

Thanks Again

 

More on Winter Tires...

Winter Air Pressure...You Can't Just Set It...And Then Forget It

If you’re like most drivers, every once in a while you check your tire air pressure. You set it when you get new tires or when they “look a little low on air.” Unacceptable!

Tire pressure has to be checked periodically to assure that the influences of time, changes in ambient temperatures or even a small tread puncture haven’t caused it to change.

And since tires don't really carry the weight of your vehicle...the air pressure inside them does…maintaining correct air pressure is a requirement for good handling, traction and durability (so don’t immediately blame the tire manufacturers for poor performance). The tire pressure recommended in your vehicle's owner's manual or on the tire information placard is a "cold" pressure, so check it in the morning before you drive more than a few miles.

But, the colder winter months are the most critical times to check your tire's inflation pressures. Here’s why you can’t just set it and then forget about it: Air is a gas which contracts as the days get shorter and the temperatures get colder. For every 10 deg. Fahrenheit change in outside temperature, your tire's inflation pressure will change by about 1 psi (up with higher and down with lower temperatures).

In most parts of the country the typical difference between average summer and winter temperatures is about -50 deg. F. That difference results in a loss of about 5 psi, which will sacrifice tire performance and treadwear!

Consider this, too: If you are fortunate enough to park in an attached or heated garage you will also "lose" pressure when you leave its warmth and venture into the real world outside. So add 1 psi of "cold" tire pressure to compensate for each 10 deg. temperature difference.

And after you’ve checked your air pressures, don’t forget to put your valve caps back on and double check that they’re tightly screwed on. Leave them off and moisture can freeze in the valve and allow your now precisely measured air to escape. Kind of defeats the purpose

 

Same with my E500 / TPM... but I've really come to rely on it for making sure the pressures are good. BTW - ny dealer says that you need to use plastic valve caps with TPM, otherwise the readings may not be reliable.

 

When TPC 1st came out, we were told that we had to use the plastic caps because the steel caps will cause false readings.

Now MB says the steel caps do not affect the readings, you can use them but electrolysis will happen between the steel cap and aluminum stem.