How to make sense of the TPMS?
Thread Starter
Junior Member
Joined: Mar 2020
Posts: 56
Likes: 3
GLC 300 2020 SUV
How to make sense of the TPMS?
I have a new 2020 GLC 300.
I understand that the Tyre Pressure Monitoring System cannot be perfectly accurate. But after filling all my tires equally to 220 kPa using the same machine, it still shows different pressures on different tyres. And what does the option to "use the new pressures as reference values" do?
I understand that the Tyre Pressure Monitoring System cannot be perfectly accurate. But after filling all my tires equally to 220 kPa using the same machine, it still shows different pressures on different tyres. And what does the option to "use the new pressures as reference values" do?
Super Member
Joined: Sep 2017
Posts: 738
Likes: 163
From: Orlando, FL
2016 E400 Coupe (C207)
My car is the same way; there just isn't that much precision in consumer air pressure measuring devices. The only way I can get mine relatively close is by overfilling them all slightly and then bumping them down incrementally (after multiple drives) until the car's monitoring system shows them as generally even. That's a job for true OCD people like myself.
The "Use new pressures as reference values" function allows you to overwrite the last stored values to reflect whatever pressure is in them at the moment. For example, let's say your tires are currently filled to 45 lbs and that is the reference value stored by the car. This means that, if the pressure drops below 45 lbs, a warning will come on in the instrument cluster. Now, let's suppose you've decided that the ride is too firm for your taste at that pressure, so you drop all four tires down to 44 lbs. After making this adjustment, you'll want to "Use new pressures as reference values" so that the car doesn't now warn you that the pressure has dropped from 45 lbs to 44 lbs.
The "Use new pressures as reference values" function allows you to overwrite the last stored values to reflect whatever pressure is in them at the moment. For example, let's say your tires are currently filled to 45 lbs and that is the reference value stored by the car. This means that, if the pressure drops below 45 lbs, a warning will come on in the instrument cluster. Now, let's suppose you've decided that the ride is too firm for your taste at that pressure, so you drop all four tires down to 44 lbs. After making this adjustment, you'll want to "Use new pressures as reference values" so that the car doesn't now warn you that the pressure has dropped from 45 lbs to 44 lbs.
Thread Starter
Junior Member
Joined: Mar 2020
Posts: 56
Likes: 3
GLC 300 2020 SUV
My car is the same way; there just isn't that much precision in consumer air pressure measuring devices. The only way I can get mine relatively close is by overfilling them all slightly and then bumping them down incrementally (after multiple drives) until the car's monitoring system shows them as generally even. That's a job for true OCD people like myself.
The "Use new pressures as reference values" function allows you to overwrite the last stored values to reflect whatever pressure is in them at the moment. For example, let's say your tires are currently filled to 45 lbs and that is the reference value stored by the car. This means that, if the pressure drops below 45 lbs, a warning will come on in the instrument cluster. Now, let's suppose you've decided that the ride is too firm for your taste at that pressure, so you drop all four tires down to 44 lbs. After making this adjustment, you'll want to "Use new pressures as reference values" so that the car doesn't now warn you that the pressure has dropped from 45 lbs to 44 lbs.
The "Use new pressures as reference values" function allows you to overwrite the last stored values to reflect whatever pressure is in them at the moment. For example, let's say your tires are currently filled to 45 lbs and that is the reference value stored by the car. This means that, if the pressure drops below 45 lbs, a warning will come on in the instrument cluster. Now, let's suppose you've decided that the ride is too firm for your taste at that pressure, so you drop all four tires down to 44 lbs. After making this adjustment, you'll want to "Use new pressures as reference values" so that the car doesn't now warn you that the pressure has dropped from 45 lbs to 44 lbs.
Super Member
Joined: Sep 2017
Posts: 738
Likes: 163
From: Orlando, FL
2016 E400 Coupe (C207)
Unlike what's implied in my example (which was merely intended to describe the concept), I believe the TPMS system alerts are actually displayed when the pressure drops by a certain percentage from the reference value within a given period of time.
