mellonc

My tire pressure setting is 33/35 front/rear - for having up to 3 people in the car and some luggage. Why the difference between front and rear??? is it just a function of luggage taking up weight? I was told that I should set it at 35/35 and keep it that way from my other MB drivers around my town. I have no idea.

I did try running them at 38 all around and it was painfully bouncy. Run flats don't help.

belarus27

~32-34 fronts
~35-37 rears
on cold!
i dont know why (maybe weight distribution , pressures , different tire sizes (if staggered), etc) so i just keep them around there .

thefisch

Exact same for me.

Zavato

Interesting- I'm running 36 psi all around. I don't have staggered tires. Ride at 36 psi seems fine

DESAL

In hot all year around South Fl with standard tires (No run flat) Nitrogen filled. 35 front 38 rear. Have 24,000 miles and 4/32 on tread.

IgorE350

What about 4matic? i run my 4matic 35 all around

degeja

where are tire tread thickness measurements and loading at those pressures?
Wear is highly load sensitive; ie fully loaded w/ 5 280 lb passengers and trunk with several hundred lbs. vs 1 to 2 people and empty trunk.
TP label only gives one recommendation.

jahquan3

I have a staggered setup and I run 34 Fronts - 40 Rear but with the change in temps almost daily my PSI readings are all over the place. It was 60 degeress two days ago and it's 21 degrees today. So this morning it was reading 29 Front and 35 Rear

The G Man

Higher pressure in the rear tires will decrease oversteer, unless you plan to drift your Mercedes on the track, just inflate all the tires the same for even wear.


http://www.tirerack.com/tires/tirete....jsp?techid=58

cetialpha5

Actually the pressures are listed inside the gas cap cover. I think it's 32/33 for front and rear if you're going to going less than 100mph. For over 100 mph, it's 35 and 42. I don't think I've ever gone over 100 so I try to keep it at the first set of numbers. If the tires are hot, add 4 psi.

belarus27

so is there a golden middle ? seems like eveyrones pressures are different lol

jahquan3

I go at least 90 every day (Well when I'm in Mexico

I push 100 a few times a week since I do a ton of highway driving and yes, after about 15-20 minutes of driving they'll heat up by 4 PSI or so.

I even noticed on days when the sun is hitting a certain side of the car that side will be a couple PSI higher then the other. Eventually it tends normalizes.

jahquan3

I think as long as you're fairly close to whats on the gas cap or inside the door label you'll be set. If you have 18s or higher I'd always lean towards the higher figure allowed. The side wall is just so thin that any additional cushion might be helpful.

jadatis

Your strange rear higher then front is because advice is given for fully loaded only.
In Europe before 2000 normal use advice was determined for axleloads determined by carmaker for 3 persons and a little load ( as you use).
And this advice was mostly front higher then rear.
As far as I know in America always Gross axle weight ratings where filled in the formula to calculate tire pressure advice.

but nowadays also in Europe normal use advice is calculated for GAWR's and this is 9 out of 10 cars rear higher then front so rear higher pressure.
for heavy use they often highen up rear to pressure needed for maximum load, wich is called referencepressure, and is lower then the given maximum cold pressure on sidewall of 44 to 51 psi for Standard load tires.
reference pressure though is always the same in American system and 35 psi , European system tires 36 psi with exeptions possible.
With this reference-pressure you could drive up to 160km/99m/h with given maximum load on tire , without damaging the tires by overheating.
For higher speed there is an official system of highening up the reference-pressure with a system depending on speedcode of tire.
For that the difference between cold referencepressure and maximum cold pressure is used, but also for alighnment ( camber angle above 2 degrees , tires like this on the axle/-\ seen from behind or front ).

If you can give me 100% acurate determined loads on seperate wheels , and the maximum speed you wont go over for even a minute in your use, and the tire-data as maximum load ( or loadindex) , kind of tire to determine referncepressure, and speedcode, I am able to calculate a save pressure for you . But this 100% acuracy is never possible , so I calculate with as much possible reserve , wich still gives acceptable comfort and gripp.
In the end by the inacuracy of measurements of loads and pressure , it can end in a pressure that is yust enaugh to give no damage to tires by overheating.

Greatings from a Dutch Pigheaded Selfdeclared tirepressure-specialist.
Peter

mellonc

OK go it. 35 all around for me from now on.

jadatis

If you give me empty weight of car and GAWR's and GVWR, I can estimate the axle weights, and calculate a pressure for you .
this could turn out to be lower then the 35 psi , mayby the 33 psi front is also enaugh for rear in your use.
But higher pressure is better for fuel saving.
I am also able to estimate the effect of that in gallons/100miles or Liters/100km, whatever you want.

DESAL

My last few cars let me get a readout of pressure so I have simple rule of thumb. My car is garaged. The tire pressure therefore as I leave the garage is pretty consistent. I set the pressure 1/2 way between load and non-load amount which is about 2lbs above the non-load amount. So if I see that the pressure has dropped, I head to Costco and get a refill of nitrogen refill. (I know nitro vs good old fashion air) Costco always add way to much. So the next morning before I back the car out I take my tire gauge and adjust the pressure to where I want it. Right or wrong my goal is consistency.

mellonc

The empty weight is 4400 lbs or 2000 kilos. I don't know the GAWR or the GVWR - MB doesn't seem to publish those.

badbenzz

I always set the pressure to the manufacturers recommendations in my case 39 and 41 cold

cetialpha5

How are you reading that card? I read it as 39 for the front and rear with a normal load and 41 all around with maximal load. So do you have them all set at 39 or 41? Or do you have it set at 39 on the fronts and 41 on the rears?

badbenzz

Based on the crappy roads in Los Angeles I keep the air at 41 psi front and back cold

jadatis

That is something for a start, but need the tire-data too.
My estimate is that this emty weight is 45%+300lbs/140kg front and 55% - 300 lbs/140kg rear= Front rounded 2300lbs/1050kg and rear the rest 2100lbs/950kg.
This is a method I once determined of weights I read of only 2 different cars, with motor in front ( as almoast every car).
If this is the real empty weight and not the given weight by the car-maker.
In Europe you pay tax by the weight of car, and so standard model is given weight for and what is added does not count for taxweight, so empty weigh in Europe you can add at least 100kg/220 lbst to to get the real empty weight.
Probably this is America not the case.

But will go from this empty axle weights , knowing estimating is dangerous.
So keep this in mind using my advice.

Driver and co-driver are seated in front seats wich are about in the middle of the 2 axles , lets keep it a bit to the front axle.

Gives their weight devided 55% on front and 45% on rear ( ooh ooh again estimated). Asume both 80kg/175 lbs x2=160kg/350lbs gives front +88kg/192.5lbs and rear + 72 kg/ 157.5 lbs.

Rear seated person, the 3th of your normal use is seated closer to the rear axle, I state it 1/5th of the wheelbase ( distance between front and rear axle). This gives 4/5th on rear and 1/5th on front of that person .
Asume again 80 kg / 175lbs gives front + 35 lbs/16 kg and rear + 64kg/140lbs.

Then the lugage in trunc is above or even behind the rear axle , lets say 20kg/44lbs gives front + zero and rear + 20kg/44 lbs.

Dinner time so will be continued later.

EDIT:
Did not have the time after dinner so now a few days later.

First add up the axle weights of the different loads in car and car itself.

Front axle in kg :1050 +88+16+0=1154 kg. x 2,2 = 2539 lbs.
Rear axoe in kg: 950+72+64+20= 1106 kg x 2,2 = 2433 lbs.

If you make these weights above 85% of the weight you calculate of look back the pressure for , to my conclusions you still have acceptable comfort and gripp, but I realise this is discusable and sertainly comfort is subjective, some write you can go much further.
For this you need to devide the axleloads by 0.85 to get the weight to look back.
And always there is a weightdifference R/L on the axles wich can even be crossed F/R.
So I will use 90% Loadpercentage ( as I babtised it). will go on in LBS because this is used in America I think.

Front 2539 lbs/0.9=2821 lbs to look back in Pressure/loadcapacity list but better calculated with the to natures law ideal formula, wich mine ofcource comes close to.
Rear 2433 lbs /0.9=2703 lbs to look back or calculate.

Then you see that rear lower load so lower pressure needed, for what was in earlyer days normal use pressure in Europe.
The maximum load of a tire is given for up to 160km/99m/h so if you use higher speed the pressure loadcapacity lists can not be used.
But who drives faster?

And that gives my answer to last post of thenew3, below this post, about the different advices for the same car.
It is a matter of opinion of what the car-maker thougth save in time, nowadays the car- maker can be held responcible if they give an advice and only one uses higher weights or speed for that advice and tires damage and accidents and injuries or death people.
Especially the rear axle is often overloaded in when GVWR is reached, by place the extra load is placed in that case.
So Rear axle is mostly adviced on a pressure that is enaugh for overloaded situation with maximum technical car speed used.
Or yust Maximum allowed cold pressure of tire, wich is not the referencepressure as I already wrote.

So with their advice you might experiënce some discomfort, but people get used to that and think it is what it is.
So if you want to go lower , it is your own responcibility, you must realise that. Even I dont garanty my advice to be absolutely save.

But if you know how it works to laws of nature, you can make a reasonable pressure with enaugh reserve .

DESAL

OMG Please, Please don't have that extra piece of cake you will have to start all over again. But think we all appreciate your math.👍

El Cid

Do what the owner's manual says. This is for comfortable, safe ride. Also for best tire wear. E Class has two different TP recommendations depending on model.
If instructions for your car in Operator's Manual says different TP's front and back that is what you need to do.
I do generally tend to run mine about 2 lbs. over and check for even tread wear every six months or so.
I carry two - three people and some luggage occasionally and never change the pressure.

thenew3

I find it interesting there are so many different tire pressure recommendations from the MFG for the same model car.

I've seen 3 different E350 W212 with 3 different recommended pressures. On my wagon, MB recommends 35/41 F/R cold normal load. Non-staggered tire/wheel with 4matic.

On a loaner E350 W212 sedan it was 39/39, yet on another E350 loaner it was 35/39.
Both of those loaners had the same wheel and same model/size tires.

There must be a logical reason why so many different pressure recommendations.