hello_world

GUys,

I feel i have been running on low tire pressure for about months now. I can feel the general sluggishness now. Could you guys let me the know what should be the correct tire pressure i should be running . I am the only one to drive my car i.e no heavy loads. Its a 2014 C250 running on stock tires (continentals))

I got the foolowing info from the B pillar and fuel cap: (i have posted pics here as well http://imgur.com/a/h3Owk )

B pillar :

Cold tire pressure :
Front : 33 PSI
Rer : 41 PSI


Fuel cap says Cold tire pressure but displays max load pressures :
30 psi and 38 PSI

What should i folow..

I did a couple rounds now to get readouts of my current tire pressure . It said :

Fron t : 25 and 25
Rear : 33 and 32

What should i do ? PLease help..

michail71

Standard is always the door pillar, which is also what the manual say to go by.

I was confused myself about the fuel cap.

I have mine set to 33/41.

hello_world

That means i am severely under inflated. Will go right now and get it all increased by 3 PSI . that way in longer drives when the air heats up, it will stay under those limits. Thanks man

michail71

Apparently this question pops up frequently and confuses everyone. Here is a thread from the E-Class forum.

https://mbworld.org/forums/e-class-w...-pressure.html

Seems some people go for the pillar, some for the fuel door and some people go in-between.

hello_world

Saw this from that thread you linked above :

"The pressures listed on the B Pillar are the cold settings for the max load/max speed. These are the maximum you should set the pressures on your car and should only be used when the car is fully loaded or if you plan to run at sustained high speeds (think Autobahn, so uncommon in America).

The pressures listed on the gas filler flap give you normal cold pressures and cold max load pressures. For regular driving when not running a full load of people/cargo, the normal cold pressures (lower numbers) should be what you run.
"

The only question is if you see the images i have linked with this post , the filler cap clearly says 30 psi/ 38 psi max load ( what is it for though ? Front ? REar ? SPare ?). I never run on max load..its just me..So putting it 33/41 as you suggested will be wrong is it , given that air pressure will increase when i drive for longer distances.?

michail71

It is confusing. It says "30/38 max load" but the higher numbers are 33/41 on the pillar. Wouldn't max load be 33/41 for driving 100+MPH?

Always take measurements and fill to cold. Don't worry about operating pressure.

I may drop a pound or two after reading everything. My car came 33/41. At first I thought it was high and then saw the pillar.

But if you get serviced anywhere they'll do what's on the pillar.

But it's only a 3 psi difference. Most people run their cars way off through neglect or trusting the shops to do it correctly.

hello_world

I did a lot of digging now and found the following in the MB manual:

Tire and Loading Information placard on the B-pillar on the driver's side of the vehicle (Y page 326). The Tire and Loading Information placard contains the recommended tire pressures for cold tires on a fully loaded vehicle and for the maximum permissible vehicle speed.

This means the info on the door jamb (for 33/41 ) is for max speed (100+ mph) and max load. This is what you are running on.

The fuel filler cap says the same thing actually ( 30/38 for max load and add extra 3 psi each for > 100 mph i.e 33/41 for max conditions)

Per logic , i should keep the pressures at about 28/36 for normal load and < 100 mph.

Let this thread be an eye opener for others.

michail71

I'll probably drop down to the 30/38 or even a little lower as I have some rims out of round and a bent strut (came that way from dealer so they are fixing). It may help some with the oscillations. Plus, there is no way I'm risking a ticket for 100+.

It's a rather interesting topic. I wonder what the reason for the 8 PSI difference is between front and back? Some cars call for more upfront because of the engine weight.

michail71

I purchased a nice meter with a large dial and a bleeder valve for $14 at the auto parts store. I bled it down while cold to 30/38. From now on I think I will over inflate slightly and then bleed off in the morning. You can really dial in the pressure this way.

Once on the highway the operating pressure goes up to 33/41, roughly 3 PSI.

I think the steering has become a little heavier and not as hair trigger touchy. The oscillation I have from the bent rims isn't as bad at first but then comes back once them PSI comes up. This may fit with my other observation that the wheels oscillated more with passengers in the car.

hello_world

I bought a Slime tire inflator and Slime digital pressure gauge yesterday for about $25 from Walmart. Today morning while cold, inflated my tires to 28.5/36.5 manually.

Started the car and checked the TPM , it showed 27/36 and i did a TPM restart. The drive with these higher pressure was pretty noticable. Car seem to just run away and the road debris was much noticeable. Though nothing changed drastically. I also knda remeberes the dealer had set 28/38 when i purchased the car about 6 months ago.

Edit: i asked for opinion om reddit also. A guy replied asking me to air up mu tires yesterday. I have posted this link there so that moving forward any one can see what pressures to run on

Alfadude

I think your tires are severely under-inflated. Follow the cold tire pressure (33/41) and leave it at that. That is what the factory recommends. As you drive the pressures will go up a few pounds, but that is to be expected and already is factored in by the factory when they make those recommendations. Don't worry about that. As long as the pressure is within a couple of pounds of the recommendation when you first drive the car in the morning you are fine. Just keep an eye on the pressures going from summer to winter are teh pressures go down when it gets cold.

If it is pretty much you and an occasional passenger or two or you occasionally haul something heavy in the trunk you are fine. There are probably very few people that have to worry about the max load rating.

hello_world

Yes , I inflated my tires today. Although, 33/41 are recommended by factory for max conditions ( i.e max load and max speed). Since I normally dont have a passenger and drive to work prety much under 70 mph..i put it at 28.5/36.5 today. Thanks anyways for the reply.

Alfadude

I still think you are interpreting it incorrectly if the stickers on your B pillar and gas door are like mine.

The B pillar is for "normal" driving where it's just you and a passenger and not high speed driving over 100 MPH for long distances. The filler door is when you are at max conditions over a long period of time, which for most people is probably never.

What is on the B pillar is based on the wheel/tire combination that came with the specific car you bought; luxury, sport, etc. What is in the owners manual is very general as it is written for every model combination they sell in the C Class line. For normal driving go by what is on the B pillar.

hello_world

I cant see you thumbnails properly. Here is the photos of the labels on my door jamb and fuel filler. My fuel filler says 30/38 cold on max load . B pillar says 33/41 . PLease check out my pics here http://imgur.com/a/h3Owk

Alfadude

Those are the same exact stickers I have. Note on the fuel filler door it states MAXIMUM LOAD. How often do you REGULARLY drive for a PROLONGED period of time with a maximum load, like 4 people and a full trunk of bowling *****? If the answer to that is pretty much never, then go by what is on the B pillar. It's as simple as that.

hello_world

Dude i think you are mis reading it. My fuel filler cap says 30/38 MAX load. IF i go by b pillar which is 33/41, it will put me well above the max limit. If i understand correctly, recommended pressure is higher for a 'full laden' car. That is why a spare tyre has to be kept at higher pressure.

Your fuel filler cap says 36/39 . Maybe i am understanding differently. Please correct me if wrong.

From the manual :

If the tire pressures have been set to the lower values for lighter loads and/or lower road speeds, the pressures should be reset to the higher values:
if you want to drive with an increased load and/or
if you want to drive at higher road speeds

This means for max conditions -> increase the pressure. For normal -> decrease the pressure. Since i drive in normal load conditions i kept it low and not 33/41 which would correspond to max load conditions

DapperStyle

Hey I think you are misunderstanding the reason for the lower numbers on max load. Alfadude is right the numbers on the door jamb are for normal daily driving. The reason that the numbers on the fuel filler door are lower for cold is because of the extra added weight + driving 100 MPH will raise the PSI substantially. The correct pressures are what's located on the door jamb, I even keep mine a little higher during the winter months currently at 35/42 and I'm usually driving alone. Driving with tires as under inflated as yours will lead to uneven tire wear, worse handling and bending your wheels more easily on potholes. You mentioned you had a wheel out of round, very low tire pressure could've contributed to that.

Trust us use the door jamb and since it's winter add a PSI or 2 and reset your TPMS.

hello_world

Are you sure about this ? The manual seems to say other wise

Out of round ? I dont understand this

Yes i have inflated it to 28.5/36.5 currently.

Also from this thread : https://mbworld.org/forums/e-class-w...-pressure.html

The pressures listed on the B Pillar are the cold settings for the max load/max speed. These are the maximum you should set the pressures on your car and should only be used when the car is fully loaded or if you plan to run at sustained high speeds (think Autobahn, so uncommon in America).

The pressures listed on the gas filler flap give you normal cold pressures and cold max load pressures. For regular driving when not running a full load of people/cargo, the normal cold pressures (lower numbers) should be what you run.

It is definitely a very confusing stuff. The pressure i am at now (28.5/36.5) is the pressure which the dealer gave me 6 months back . I am gonna stick to this.

michail71

It is confusing, the fuel door says 30/38. Then it says to add +3 for driving over 100 MPH or maximum loaded vehicle, which equals the the 33/41 that is on the pillar.

So it would seem the pillar is for maximum conditions while the fuel door is what they probably recommend on the minimum end.

As for the out of round, that was me. It was not caused by low pressure. The previous person who leased the car I bought hit something hard enough to bend two rims and the strut on the right side of the car.

hello_world

You are correct man. I am going per manual only which says that the info on door jamb is for max conditions only.

You would hope for the amount we are paying for these cars, the manufacturers have an easy way to convey the recommended tire pressures instead of us running like headless chickens

Carsy

My rears wear the inside shoulder prematurely. Have done so since new. They are perfectly within specs . What occurs is that the shoulders develop splits which eventually penetrate to the extent that air escapes.

I rotate which helps but am now running 40psi + to encourage more wear in the centre of the tread.

michail71

The C250 is staggered so we are out of luck on the rotation. Perhaps we could rotate pressures? lol.

Alfadude

No where on the door jamb does it say the pressures listed is for max load. All is says is cold tire pressure. Max load refers to the amount of weight you are loading ion the car. It does not refer to max tire PRESSURE. Maybe that is why you are confused.

Does your car feel sluggish handling when making quick transitions? If so, that would be from how low of a pressure you have been running. Do you see some feathering wear on the very inside and outside of the tires? That would be a sign of low pressure also.

Can you post from the manual where is says the B pillar pressures are for max load?

michail71

Page 323 and page 323 for the 2013 C-Class Owner's Manual.

It basically says pillar is the maximum load settings and the fuel door is the normal load settings. The fuel door just says +3 for max load, which matches with the pillar.

So the correct answer is between 30/38 to 33/41 depending on load or insane driving speeds.

If you go to the loading section it begins to read like airplane loading instructions.

Alfadude

I stand corrected....I think. I looked in the manual when I went out to the car and it does says the B pillar is the maximum rating and in looking on the sticker on the B pillar it ways "Extra Load" under the tire sizes the car came with. The gas door says "maximum load". Makes no sense. Every car I ever owned had the normal pressures listed and a max load rating, usually right next to each other. Unless what Mercedes recommends is the max rating as "normal" every day driving. Something that is typically an easy thing to reference is all but indecipherable. Odd.

I also looked at all the load rating information and it is way more than probably 99.9% of the users would ever need or care about. Sounds like a lot of legalese.