GLCer

What tire psi are you using for stock Pirelli tires on 18" wheels?

Sticker on door says 35psi for front and 42psi on rear on ours. I read somewhere in the service manual and it states 32psi all round for N America.

rbrylaw

Don't follow the sticker on the door. Follow the sticker on your gas cap filler door.

GLCer

Thanks! 32psi on gas cap. Just checked and ours was delivered with 42psi all round. No wonder it felt a little harsh

rbrylaw

Yes, that would make the ride a bit harsh for sure.

tron786

Is the TPMS system a real time and accurate system with proper sensors?
Always drove BMW that only had a "possible flat" warning as TPMS with sensors is not mandatory in my country.

GLCer

I think its pretty accurate to +/- 1-2psi (unless you plan to race on the track )however you need to drive the vehicle for a few minutes before the psi information registers on the dashboard.

Found this, not sure if helpful
http://www.edmunds.com/car-safety/ti...y-on-them.html

ay55

Has anyone confirmed this with MB dealer or MBUSA? Shouldn't they correct the tire pressure before delivery? And isn't the difference from 32 to 42 so much that 42+5 (warmed) might even be over the max permissible?

GLCer

If you look at your tire , there should be max pressure rating you should not exceed, so you can kind of experiment lowering pressure from that point to see what works for you but with all things in life there are trade offs depending on grip, comfort, fuel economy, tire wear, weather etc. I reduced pressure to 32psi as shown on the fuel filler cap but found the ride quality compromised, it was very harsh with the run flats and at some higher speeds, found the balancing affected , slight vibration. Rather than bring it back to the dealer to check balancing, I experimented and am now using 38-39 psi at 32-40 deg F cold temp all round and like it better than 32 psi all round. For longer trips or in summer I may reduce 1-2 psi since tires will heat up and experiment again .

larrypmyers

When feasible check tire pressure in the morning before the vehicle is driven.

Follow guidance on the tire pressure decal located inside of the fuel filler door.

re_tired

it may be different in AU, but the sales exec said the warning system runs off the ABS sensor. This detects when one tyre is flat due to rotational speed and sends out an alert. I think I heard him correctly

Teckno

Question.
Given the MOE tires are thicker and I guess heavier, would they benefit from being filled with Nitrogen, to reduce tire heat and provide a more constant pressure and temp ?
Also do any members run your tires slightly higher psi/kpa above the recommended sticker values ? If so, what do you run them at, front & rear ?
Thanks

re_tired

Teckno, can't help with the nitrogen, however I was told that if different pressures are run then a change to the car config is required

fabbrisd1

Nitro fill frankly is a world-wide sham mate... check inside of fuel filler door for MB recomended tire pressures - YES new Mercedes are shipped with higher tire pressures during transport to prevent "flat spotting - and YES delivering dealers can "miss" correcting tire pressure for delivery.

Overall - a 2lb change in tire pressure will change the driver's drive/feel - so best starting with "recommended" pressure to drive that for one week - then push up 2lb's and drive that for a week.... etc.

Overall - as pressures increases tread life increases - as tire pressure drop tread life decreases.

The TPMS system is designed to be a Emergency Alert to lost pressure on the road - TPMS is NOT designed to provide tire pressure for fill - TPMS is quite sensitive, including quickly measuring pressure differential due to temp.

Keep the beat !

larrypmyers

Your correct. As part of pdi the technician should check and adjust tire pressure as specified on the inside of the fuel filler door.

The first thing I did when I arrived home from the dealer was check tire pressure. And it wasn't close to what was called on the placard.

ay55

Thanks. what was your reading?


I used my own gauge rather than TPMS, and got 35 psi from front tires (cold) and 42 from rear tires (cold), which exactly but mistakenly matches the placard on the driver's door. All four tires are the same brand and model. The maximum permissible pressure of them is 51 psi.


I noticed this problem and corrected it after driving for hundreds of miles when my manual learning progress reached the chapter of tire pressure. Fortunately, 47 psi (warm) didn't cause a problem, at least I am not aware of yet.


But I still believe there was a fault in the MB internal process. A technician must have followed the wrong placard to adjust tire pressures. Just wondering whether other MB car models have two placards with different recommendations too.

larrypmyers

My feeble memory seems to recall 42 psi.

Was pleased to discover, after adjusting the pressure, that tpms pressure and my tire gage pressure were identical.

Driving a bit with over inflated tires is of little consequence. On the other hand, driving with under inflated tires will guickly have a deleterious effect on them. Under inflation is the primary cause of premature tire failure.

No excuse for delivering a new vehicle to the client with improperly inflated tires. Nothing more than inattention to detail.

JEVA

The pressure in my tires was 42 all the way around on delivery. Seems to be a trend.

awjenni

My GLC has Pirelli Scorpion Verde 18" MOE tires. I drove it for a few hundred miles before checking the pressure. I thought the tires were noticeably noisy, thunky, especially on bumps and cracks.

I checked it and the fronts were set to 42 psi and the rear were at 49 psi.

I was less than a mile from my dealer and took it in for them to correct it. I drove it away and it sounded and handled MUCH better. They set it to to 36 psi both fronts and rears... which is not exactly in compliance with the filler flap. The filler flap calls for more pressure in the rears than in the front when heavy. When lightly loaded, it calls for equal pressures, I think 32 psi.

Al

07SGT

I am on my second MB and both were bought new from the same dealership. And both were grossly over inflated. I think, at least in part, they are trying to influence MPG so owners will be impressed. I cannot think of another reason to grossly over inflate.

jamespaul

so what tire pressure are you guys using now?

I am using 36 psi when cold

larrypmyers

Cold..32 psi.

ralawren

There are different pressures for the 17" vs 18" Wheels. I don't believe USA gets 17s so the 36 lbs is misleading. Check the pressures listed in the gas cap.




Photo from Inside Gas Cap shows pressure for three different size wheels/tires.
https://www.dropbox.com/s/3mgpvqncp4...sure.jpeg?dl=0


My USA GLC300: R18, R19 and R20 are all 32 by 32 on Cold Tires. (From gas cap)
The plaque on the drivers door sill states I have R18 Wheels/Tires and the settings are 35 Front, 42 Rear.
Photo of Door Sill
https://www.dropbox.com/s/kyg5itt1vq...Sill.jpeg?dl=0


Which is correct? I guess the door sill since it is specific to my vehicle and only lists the actual size tires/wheels that are on the car.

Sigp232

19 inch 34 cold

ralawren

They are grossly over inflated for transport on the ship. It keeps the suspension from moving around too much. The PDI at the dealer is not bothering to check and adjust the pressures. I have purchased three MBs from the same dealer since 2011 and all three were delivered without the air pressure being set correctly.

Flubadub

Don't know why, but the door info should be specific for your installed tire size, but lists only the maximum load pressures. The fuel door sticker gives both max load and normal load pressures for all possible factory installed sizes.
I agree with fabbrisd1, the N2 "miracle" myth has been well exploited by tire sellers worldwide. Few people know that the air we breathe and fill our tires with is already almost 80% N2!!