Just got my new glc300 and the tires are all inflated to 42 psi, I changed them all to around 32.5psi following the recommended pressures on the fuel door.

what's the optimal pressure you guys have found to be overall the best for your tires

 

Pressure on the fuel door is correct. If you have OEM tires on it plan to replace them around 20,000. Factory tires are junk. I replaced them with Bridgestone DriveGuards with 60,000 mile warranty.

 

+1, use the fuel door recommendations. I live in a climate that has hot summers and cold winters, and keep my 19s at 32 summer and 34 winter. I had the OEM tires replaced at 4500 miles with (non-run flat) Goodyear WeatherReadys. For me they are a big improvement in ride with no compromise in handling.

 

At 32,000 miles replaced the oe Pirellis' on my 16 GLC with Bridgestone Drive Guards. The Pirellis were not completely worn out. Probably several thousand miles remaining. They were, however, annoyingly noisy and plus was getting ready to do a 1,000 mile+ drive.

After a dealer all wheel alignment, noticed the vehicle ride to be extremely harsh and noisy. The next morning a pressure check indicated 37 psi. Evidently as part of the alignment, the tech. adjusted the pressure. I reduced it to the specified pressure, 32 psi, indicated on the fuel filler door. All is well.

My early observation of the Drive Guard is favorable, much superior to the Pirellis. It remains to be seen how long tread life will be. As Mikbar has posted the tire comes with a 60,000 mile warranty. We'll see.

 

I know the OP is asking about tire pressure for 19" tires but for what it's worth I'm running 18" Pirellis and have found 32 psi all around to also be the magic number.

 

Wow thats way to much now I have to check mine thanks for this!

 

Tires that came with my 2018 GLC300 were absolutely junk....needed to be replaced with less than 40,000 miles. Note.....I checked tire pressure fairly regularly.

Just an added note.....I will never buy another Mercedes EVER! I have done more repairs than any other car I have own. Making things worse....have to drive 2 hrs to get to the nearest dealership.

• Controller that resulted in my XM radio to not work. Fortunately, that was covered under warranty....just barely.
• Tires...as I mentioned earlier.
• Now, a PCV valve (not what Mercedes calls it) that will cost over $2k to replace. In most cars, anyone could replace for just a few dollars....and a few minutes. Not Mercedes. It will require to be in the shop for a full day! When I questioned the dealership on cost and time, they told me they do 4 or 5 vehicles every week. Car only has 42k miles.

Prior to this, I owned three Caddy's. Only ONCE, did I need to take any of the Caddy's in for work beyond routine maintenance.

I ask myself what will be next....and how much it will cost.

 

With your engine, cracked piston head has been reported. Read up on it just so you can make a plan.

 

I have had 6 Mercedes, for the most part they have been great. The one thing that I have never had is a Mercedes passed it’s warranty. At that point my feeling is let someone else enjoy it…..

 

I believe it was an eroded valve seat, incorrectly reported as cracked head.

I'm uncomfortable having any car past the warranty any more. My 96 Chev pickup is by far the most expensive car to maintain, < 100,000 miles.

Buy an extended service plan if worries about repairs hamper your enjoyment of your car.

 

Find a good independent Mechanic and DO NOT go to the dealership. That is part of your problem.