PeachParts Mercedes-Benz Forum - Tire Pressure 420 SEL

I knew I would have to explain this eventually so, here goes ....

I don't know if you remember the quote about the nine scariest words you can ever hear and if you don't here they are "I'm from the government and I'm here to help". If you do remember the quote then you are 1 step ahead of the game.

I am going to explain this in two time periods the first time period is "Pre-ERO" and the second one is "Post-ERO". The ERO part is "Explorer roll over" which is when people in the southern states driving Ford Explorers were having tire blow outs from running to little air pressure in their tires, thus overloading and over heating them, and flipping the trucks over.

so, Pre-ERO
German vehicle manufacturers would list 3 to 4 different pressure recommendations based on vehicle usage.
#1.) around town driving
#2.) winter driving
#3.) high speed driving
#4.) fully loaded driving

Onto the Post-ERO times and the nine scariest words to hear

Our government decided that in our overly, litigation happy, society they needed to protects us from our own lack of personal responsibility. I mean can you really blame them. Nobody should be forced to actually read and understand their owners manual let alone follow some basic common sense rules. Our government enacted legistation called The Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act regarding recalls, tires and the related air pressure. Here are some of the highlights as it regards to this question:

#1.) tire pressure monitoring devices must be in all new vehicles sold in the US by 2008
#2.) there shall not be numerous pressures recommended by vehicle manufacturers
#3.) there must be tested to a 30% overloaded condition (previously it was 18% I think)
#4.) all tire DOT codes should be documented and recorded by tire manufacturers when the tire is sold to a consumer.

and in "congress speak" there is a whole lot of other BS in there as well.

as, Mike mentioned Mercedes has installed a placard recommending tire pressure but, per my #2 point, they can only recommend 1 pressure and they use their maximum high speed / high load recommendation

Now let's think about this
Driving at high speeds certainly helps make a trip go faster; just ask any driver who has gone "flat out" on the German Autobahn. However with the exception of events like the Silver State Classic's Open Road Rally or a driver's school on a racetrack, it's difficult to find a place that allows unlimited speeds! Remember, the tires on the vehicle should be properly sized, inflated and inspected if you plan to drive fast because the tires will be subjected to tremendous stresses.

Because of the weight they bear, pneumatic tires' sidewalls bulge and their treads flatten as they roll into contact with the road. This results in dimensional difference between the tire's "unloaded" radius (i.e., between the center of the axle and the top of the tire) and its "loaded" radius (between the center of the axle and the road). The engineer's call the difference between the two radii "deflection." Increasing vehicle speed will cause the tires to deflect quicker and increasing vehicle load will cause the tires to deflect farther (if tire pressure isn't increased).

So, unless all conditions and factors are not known there is no "correct" answer to your question

32 front and 30 rear should work fine on your car for normal driving conditions