John Chesher

My new 2021 GLC has two stickers at the driver's door panel with two different tire pressure requirements (39/46 and 35/42), any idea why and which should I use?

Teckno

Have you looked on the fuel filler door ?
usually recommend you use those figures.
that said, most owners add 3 to 8psi to MB recommended settings, as they are too soft and car response and handling improves with higher psi.

That said these pressures on sticker at 46psi seem excessive for 18 inch rims.
Here in Australis our 20 inch settings are much lower.
You need to carefully read the sidewall of your tire to see what max pressure is allowed, to minimise tire failure or blow out.

Again sticker weight seems wrong, 5 people at 100kg each = 500kg, well in excess of 418kg max rating, that’s without luggage in rear, really ??????
This is an SUV, not a small hatchback or inner city car.
Something is wrong.

glassbloke

Probably not often that you haul around 5 who weigh 220 pounds.

Teckno

Pre COVID I would agree, but post COVID I know a lot of people at plus 100kg or 220lbs, so even 4 people in cabin with 3 small airline cabin cases would max out the 418kg.
My point the rating seems wrong for the size of the GLC.

John Chesher

Vehicle is so new, hadn't had to put gas in yet... sticker at fuel door says: 32 psi normal load! Dealer had put 35 1/2 psi in the tires at delivery.
These are run-flat tires btw.

Teckno

A lot of owners in USA, UK and Aust run around 36psi to 40 psi.
mix of comfort, fuel economy and handling.
I tend to run at 36-37psi cold. If warm add 3 psi to allow for cooling down and start it at correct psi when cold.
We run All Season Goodyear run flats, previously summer Pirelli run flats.
running a few psi higher ensures even wear across tread and not just outside edge wear.
Also ensures better handling and braking under severe braking with max rubber on road.

IMturbocharged

An adviser at my Mercedes dealership had once told me about using the information on the fuel filler door. He said that is more specific to your vehicle than what is on the door threshold.

ajmtbm

yes the fuel door pressures seem to be more accurate one to follow. I ran around 36 when I had the 18" RFT and that seemed to be a good ride for me. From the dealer was 45 psi and it was an awful ride.

IMturbocharged

I'm glad that my adviser at the Mercedes dealership told me about the fuel door. In the past I always relied on the information on the door threshold regardless of vehicle brand.

High Technology

Only fine German Engineering could make something as simple as setting tire pressures so complicated. That, and inconsistent laws among various countries and also various government agencies here in the US.

The difference between the two figures on the door pillar is 4psi, which is Mercedes specification for this model/tire configuration if speeds exceed 100mph. FWIW, I have a 2020 with the 19-inch wheels and the tire pressures in the door pillar are the same as shown above for the 2021 with 18-inch wheels (35/42 and 39/46) -- again the two stickers differ by the 4psi. I view black the sticker with the VIN as the "recommended" inflation pressure, and the white as the maximum recommended (reflecting the +4psi if you will be driving over 100mph).

In my fuel filler flap it shows "normal load" as 32/32 and maximum load as 35/42 with a note to add 4psi for driving over 100mph. 32psi seems just too low -- I have NO IDEA what they were thinking there, and the maximum load figures match the door stickers (35/42 or 39/46 if you add the 4psi for high speed driving.

Slight variations in tire pressures are a personal preference that should balance your driving style with the road conditions (higher pressure typically handle better, at the expense of a harsher ride over uneven pavement). I live in a suburb north of NYC with lots of potholes, so I typically run 35/40 December-April (as 42 seemed a little harsh during the winter), and the recommended 35/42 in the warmer months (after the fix the potholes)

DrDMR

Door Sticker 1

Door Sticker 2

Gas Door

Summer Tire

Winter Tire

Door sticker 1: 45 front, 48 back
Door sticker 2: 45 front, 48 back
Gas door normal: 35 front, 35 back
Gas door max: 41 front, 44 back
Summer tire: 50 max
Winter tire: 50 max

This is on a GLE350 diesel (SUV), 20 inch rims.

I've tried a few PSI (35, 40 and MAX) and the best ride was 40 PSI (cold). The GLE handled well and ride was comfortable. Tire guy said to keep below the tire max (50psi) when the tires are warm (meaning below 46 PSI cold). He didn't want to commit to what was the best pressure - smart for a guy that looked 17 years old
I appreciate all the opinions in this thread but does anyone have access to MB's official data?
Thanks!

62bassman

I’ve been using 35psi (cold) all around for 3 years and find this to be a good setting for ride and handling for the 18” wheels.. If you’re an aggressive driver then you would best add a few pounds. This is for Pirelli RF, which I’m on my second set of and had at least another 5-6K left but changed at 28 because I like newer tires. Another consideration is what shift setting you use. People who always run in sport or sport plus are going to eat tires much faster and would probably want to use a higher pressure.

DrDMR

I agree - I believe it should be clearer while reflecting any legislation/regulations for the country where the vehicle is sold. Max speed limit in Canada is 65 mph.

Road conditions in my area (Western Canada) are very good - no pot holes and well maintained asphalt highways. The weight of the diesel engine is a consideration, plus we do a lot of longer distance highway driving (tires get warmer). We also don't load up the vehicle to max weight... so I am probably okay at 40 PSI.