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I am aware that tire pressures decrease in colder weather. While driving yesterday I got a dashboard alert to check tire pressure. The range on the 4 tires were 34 to 37 psi. My question is did I get the alert because of the variance in psi, or perhaps the system remembers the previous readings and noticed a decrease, or was it below recommended psi as stated by MB. I know some owners run their tires with 32 psi, I personally find that a little too low. The pressure that I had in the tires at the time of the alert popping up seemed sufficient albeit not even on each axle. Just curious what triggered this alert in my case. Thanks
Your car is set to expect Tire pressure at probably around 38 psi and the drop was enough to trigger the warning. I run the lower recommended pressures around 30-32 psi shown in the gas cover door (I don't remember the exact numbers) because the higher range was for when the vehicle is loaded up with 5 passengers or cargo. When you set to lower psi, you can set the new "correct" tire pressure in the "Service" menu on the driver side screen. I would say you should inflate your tires to the desired pressures, then set your car's "correct" pressures to the your new pressures so this won't happen again.
Thanks for this useful information, I was not aware regarding the new “correct” setting. You learn something everyday, thanks again
Nice.
Just a note to say that the new setting can be anything you choose, even a wildly "incorrect" setting. Just inflate the tires to the intended pressure, then "accept" these as the "current" settting.
It may not be correct - it's just your "chosen" pressures. I have different pressures for my Winter tires than my Summers, for instance.
It's a good ideal to let the car know your preferred inflation, so it alerts you to seasonal pressure changes, as well as a quick loss of air.
It has been my experience with MB's that the pressure set by you has a tolerance of about 4 pounds from your threshold. Once you exceed it, over or under the TPMS system will alert you. I have ours at 35 pounds pretty much year around down here in South Florida.
I had a tire shop do my winter tire swap a couple of weeks ago and they aired up to specs on the door frame - something over 45 I believe, and they reset the TPM setting. When I got home I deflated to 36 and discovered a leak in one of the tires (you can probably guess which one from the photo). I aired that tire up to about 50 and headed back to the tire shop. Along the way I got some never before seen graphics (warnings) on the TP screen obviously because of the drastic difference in actual tire pressure from the TPM setting.
Tire got fixed and after "educating" the staff about ignoring the door specs on a Mercedes and referring to the gas filler door for TP, and resetting the TPM "OK" setting, all is well.
mild temperature where you live, or perhaps you have Nitrogen in the tires?
It hasn't been that cold. Never thought of the nitrogen angle...that's a possibility. If the dealer filled them with nitrogen before I got the car and I've been using air to top off the pressure here and there, it would be well diluted by now,
12-01-2022, 11:42 AM
