rewillia

I have a 19 E4504S wagon with the optional AMG styling and AMG wheel set and am uncertain as to what tire pressure I should be running. The OE tires are Continental Pro Contact GX SSR MOE 245/40r19 98H. The door tire inflation table shows the PSI for normal load to be 42-Front & 48-Rear while the gas cap label indicates 34 & 34 respectfully.

A MB Dealer's Service writer told me to go by the gas tank label, then someone else at a different MB dealership told me to go by the door sticker. Who is right?

ua549

If you read the label the gas cap and door jamb label are the same. The apparent difference is in the load factor and the speed factor.
Set the pressure to your most common load and most common speed.

hyperion667

Yes.

rewillia

Not from what I'm seeing. There is still a variance between the recommended pressures with extra or max load. Called my Dealer again and they said use the Fuel Door.


Fuel Door

B Pillar

ua549

The gas cap shows max load 38 F & 44 R then adds +4 for high speed making it 42 F & 48 R. That is the same as on the door jamb.
Exactly what is different?

rewillia

Ok, I'll accept your points.

sabre3

The numbers add up for one set of numbers but that is in no way an intuitive set of stickers. Extra load normal and extra load max on one then just extra load on the other sticker. I don't blame the OP for asking the question. Confusing

joshg1001

It is weird because the door jamb doesn't give the normal load pressure. Very confusing!

fleuger99

Just generally speaking, those pressures seem low for a vehicle of this size and heft, no? I'm talking about the base pressures without the 4psi added.

ua549

The pressures seem to be normal especially with run flat tires with a very stiff sidewall. I have non-rft tires and use the extra load pressures.

JTK44

I have the OEM RF Pirelli P7 that came with the car. 12,000 miles and more than 60% tread life. I expect to get more than 30,000 miles on this set of tires.

I use the pressure on the filler cap for normal load, 33/33 + 2 lbs: 35/35 cold pressure. I find the TPS to agree with my tire pressure gauge.

Keep in mind that as temperatures fall, I find for every 10 degrees I lose 2/3 lbs of pressure. Ride is just fine at 35/35. Proper inflation is necessary for long tread life.

I have an excellent air compressor to "top off" tire pressure as needed. For me better than going to gas station and using their air pump. For $129 one of my best investments.

Hope this helps.

abqhudson

What is interesting to me is that no one will tell you what the appropriate tire pressure is for non-runflat tires. I don't really believe that the optimum tire pressure is the same for a stiff sidewall tire and a standard sidewall. When asking Mercedes- they say use what is on the car. When asking the tire manufacturer - they defer to Mercedes. Seems like the lawyers talking.

Not sure what happened to customer service along the way.

JTK44

In my 2016 E Class Mercedes, with non RF, the recommended tire pressure was identical to the tire pressure on my 2019 E Class.

Does this help?

ua549

Because using non-runflat tires amounts to a vehicle modification MB is avoiding liability issues by not making air pressure recommendations.

Hundens

Silly isn't it. I posted on this myself a short while ago. The fellow at Costco (who use nitrogen) went with the door jam numbers (42/48) which is really excessive and leads to a harsher than necessary ride. It is the same as the max load plus high speed pressure addition that is on the fuel door. For normal driving I go with 35 all the way around. If I am loaded up and driving cross country I go with 38/44. I guess this is just a manifestation of the MB talent to make things more difficult than they need to be. I've had the customary number of automobiles and never one with this confusion.

rewillia

Well if nothing else, this post & threads just goes to show me, that I'm not the only one confused about the subject of tire pressure and the way MB chooses to communicate such in the form of the B-pillar door jam and the fuel tank fill cover lid.

ua549

I never found it confusing because at one time I switched tire pressures each week due to loading 900 pounds of kettlebells in the car for a weekly trip to a Saturday market. Once they sold I didn't have to change tire pressures. The car never leaves the city.

2012 merc amg

Yes, 35 all the way around is the simplest thing. A lot of the time after getting the car serviced you need to let tire pressure out generally. A lot of places insist on going with the higher pressures as they think you might go out on Alligator Alley or something and try to break a world speed record, so they set em high because of liability. Best to carry a tire pressure gauge in the glove box so you check them regularly and let air out if needed.

rewillia

So after all this (guidance on deciphering of the labels), I've adjusted my pressures downward from the 42/48 set by my MB Dealer to 35/35 based upon the "Normal Load" for the 245/40R19 as indicated in the fuel fill door without adjusting the +4 for driving at speeds at or in excess of 100MPH.

jhpmbusa

also, this is cold tire pressure, as after the tires warms up the pressure increases by like +3.

ua549

Pressure will increase/decrease ~1 psi for every 10°F change in ambient air temperature. That said tire temperatures can easily increase by more that 50°F while driving. When I purchase replacement tires I get the highest speed rated tire because speed ratings are really temperature ratings.

dudley07726

I have mine at 35/35. The door jam numbers are for full maximum load. I had small argument with the Costco tire guy. They follow the door jam. I told him that its listed there for full loads. I had to show him in my Audi book for my size tire it should be 36F/33R and even had to call the Audi dealer to tell him. He now understood. When I got rid of the RFT's on the 18 E400 Coupe, I went to an independent installer and brought the Michelin Pilot A/S 3+ (purchased from Tire Rack) and they did what I asked.

rewillia

One thing's for certain. This post seems to have gotten a lot of "traction"!
Thanks to all that responded. I did learn something from it.

JTK44

It's the Holiday weekend and because of Covid we are all sitting around with nothing to do and nowhere to go!