Tom in Austin

I've been experimenting with tire pressures and find that 36 psi in both front and back feels great. So, I'm puzzling over why Mercedes calls for 44 in the rear. Is it to maximize gas mileage? With 35 aspect ratio tires on 18" wheels, I can't see any other benefit in running such high pressures and making the ride stiffer and busier.

Thoughts?

Adi-Benz

My gas cap says 30 front, 35 rear.

44 seems like a lot.

Tom in Austin

Apologies, it's actually 39 at the rear ... still the question is why higher in back than in front. Thanks

Demvang

Higher psi in rear tires because they are larger in Sports models.

C300CA

My Sports version with 17" wheels require 28 psi (front) and 33 psi (rear).
I also noticed on the gas door it says add 4 psi if driving at 100 MPH

Just204

I run 39 front and 42 rear. The wear is even on the tires.

superangrypenguin

Yes . Gas mileage

Tom in Austin

I know I'm overthinking this a bit ... if the rears can be at 39 for better gas mileage then why didn't Mercedes set the font at 39 also, or is there something different about the rear that the driver is more likely to accept high tire pressure there? I doubt the width of the rear tire/wheel requires different tire pressure, so it must have been a deliberate choice by the mfg.

BTW, I'm a Porsche 928 owner also, and Porsche specified higher pressures in their rear tires as well, no one in that forum knows a reason for it either.

catmandoob

Many theories on this, I wonder if anything concrete has ever been presented. Both theories I have heard is load balance if fully loaded and or to help create or correct for possible oversteer and understeer.

All I know is mine handles or feels best when I run 34-36 front psi and 38-40psi in the rear with 18's, with my 17's it feels best with around 30 front and 34-36 rear psi. Of course feeling ok and being correct are 2 totally different things haha, I do regularly drive uh let's just say a tid bit faster than posted highway speeds.

superangrypenguin

The width has absolutely everything to do with it.

Think tire contact patch size and PSI implications. I've written on this topic.

Over the years of the 204, MB jacked up the PSIs for both the front and rear pressures, but they have both been jacked up by the same PSI, e.g. 3PSI for front and 3 PSI for back. It has never been, e,g, 44psi for both axles.

tommiett

I also believe the high PSI is for best gas mileage, but add best tread life to the list. I just got some new Pirelli's for the rear. Tire shop told me 42 PSI rear and 36 for the front. I'm guessing.... that the PSI rating may be different for each tire and the Mercedes PSI is based on the factory installed tires.

Could be wrong..... But will go with the tire's recommended PSI as Mercedes will not give me new tires if I kill them early with too low or high PSI.

RIDE adjustments will end up determining my final PSI setting. But the 42/36 seem to be fine for me.

aowhaus

I agree, I have a 4Matic Sport and it says the same thing plus 35 all around for heavy loads. I try to keep mine almost 5 psi above that.
Also in winter weather it is advised to have your pressure a little lower for better traction in snow and ice.