Greetings All!

I started driving a 2024 GLC300 SUV in mid-April. It's at the dealer now, getting checked out due to some "minor" annoyances. While it's there, I'm driving a 2024 GLC300 loaner. The loaner accelerates "easier" when the light turns green and rolls better with less engine effort. But it's more jarring when hitting larger bumps in the road.

I looked at the tire pressure, and all four Michelins are set to 41psi on the loaner car. On my car, I keep them at 37psi, because that's what's printed on my fuel door. On my wife's 2022 GLE350, we keep them at 31psi, because that's what her fuel door says is the correct pressure.

The 41psi on this 2024 GLC300 Loaner makes the car seem more powerful and responsive. But I'm afraid if I hit a big pothole on a Chicago freeway like I did last week, the tire would deflate. At 37psi, it was an alarming jolt.

Question: WHAT AIR PRESSURE do you keep your four tires inflated to on your 2023 or 2024 GLC300 SUV... and if it's not the "recommended" pressure, WHY are you using higher or lower?

Thanks in advance for taking the time to answer my question.

Allen in Chicagoland

When we received the vehicle from the dealership, the tyre pressures were 41PSI at the front and 45PSI at the rear. Way too high.

I have them set at 37PSI, as per the manual, and the drive is much nicer!

Same as Joey, mine came with pressure in the 40’s. I keep mine at 37PSI on all 4. Does great!

Thank-you! Now that I've had 4 days with this 2024 GLC300 "loaner" and its 41psi inflation, it will be easy to decide what to do when my car is returned, if the dealer (hopefully) leaves those tires at 37psi, like there were when I dropped it off.

Thankyou for taking the time to reply. The pressure shown in our fuel-filler doors (37psi) seems to be what most forum members prefer.

Maybe there's a way to get the best of both worlds... the effortless accelerations, coasting, 90mph, that comes with 41psi, and the "cushioned/relaxed" ride that comes with 37psi.

I have my GLS tires filled above 40 psi but that's only because we normally have a full cabin with even the 3rd row occupied. I think normal in the mid-30s is probably the best for most folks.

My name is Allen and I’m in suburban Illinois.

Information about a GLS has little relevance in a GLC forum.

I’m running it they way the dealer delivered it to me; all 4 tires at 40 PSI. This might improve MPG a hair as I’m consistently getting 33 to 37 MPG highway,
including a small amount of City on both ends of each trip.

All my cars are set slightly above the recommended pressure, because of potholes. GLC 300 is set to 38 front and 39 rear for up to two people in the car.

Thankyou! Mine are now at 35psi. I'll increase to 37psi, as the fuel filler door suggests. I'd like for the car to coast with less drag, but don't want the steering to be too light. It's a balancing act I've been tinkering with since my first car in 1982, lol.

does anyone know how to calibrate the 2024 GLC 300 tire pressure sensor? I used an external air pressure gauge and found that the tire pressure display didn't match my external gauge; the car display showed about 3 psi higher than the gauge reading. somehow, I trust the external gauge more. just because the display says it is 40 psi, it may not be true 40 psi. check yours.

I trust car pressure sensor. All of my MBs and BMW sensors are matching pressure gauge reading. The car sensor will show higher tire pressure if compering manual gauge measurement taken with Cold tires in the morning AND car sensor reading after the long Ride.
Are you taking measurements under the same conditions?

It's interesting that on mornings when the sun is out and the temperature is over 70 degrees, my "Mercedes Me" app says the tires are 36 or 37 PSI.

As fall comes and the Chicago area mornings get cooler (48 to 55 degrees), the starting PSI averages 33 or 34.

I wonder what they will show when the outside temperature is below freezing in a couple of months?

I wonder what ambient external temperature was assumed when the engineers said make all four tires 37 PSI?

Tomorrow, I'll add a couple more PSI, because they now never go over 38psi, even on hot days and highway driving.

It's fascinating how a few PSI makes a different "feel" on a GLC-300, but on my wife's GLE-350, I can't feel a driving difference between the 31 PSI listed on the filler cap, and when inflated to the 40 PSI stamped on her driver's door-sill.

-Allen in Chicagoland

This reminds me of a high school physics equation: P1*V1/T1 = P2*V2/T2 Costco air pumps use nitrogen, which is more stable than air and reduces pressure fluctuation.

Physics brought tears of frustration to my eyes, but COSTCO is something I can do with my eyes closed. There are 4 of them within 10 miles of me. Thank-you sir!

In the end, it doesn't matter what the ambient conditions were when the engineers decided on a recommended PSI per tire (the value is required for minimum safe operation based on car load). You are expected to maintain the min psi even when the weather gets colder as the tire pressure is expected to drop as ambient temperature drops!

First time I've heard it referred to as a "minimum psi". For better traction on snow and ice, I've habitually kept the PSI lower than recommended, so the tire footprints are wider.

Your sticker should have a pressure for max loaded car and one for "normal" load. If you have a fully loaded car driving lower than recommended PSI tire pressure in the winter, we might see you in a "told you so" thread!