westcott

I just checked my tire pressures and was reminded how varied the tire pressures are front to back. My E550 runs 29psi in front, 35psi in the back. Not used to seeing staggered air pressure in a RWD vehicles.

Any ideas? Just curious.

no_clue

Exact pressure also apply to non-staggered setup on V6 engine as well.

Firestopper0383

I can only imagine that, the lower air pressure in the front contributes to a smoother ride and the higher rear air pressure supports additonal weight from passengers and a loaded trunk? My 03 E320 is Frt 26 PSI and Rear 32 PSI.
If you equalize to the higher pressure, you may get slighlty better MPG but I think the ride comfort may suffer a bit.

KL2DC

The lower air pressure up front also dials in a small degree of understeer (for safety).

westcott

Thats a possible explanation but on a vehicle with an airmatic suspension, seems ulikely. Load leveling for load is handled much better with air bags.

FKD

+1 It is to reduce the car's tendency to oversteer under power. They do that to a lot of RWD vehicles that have high torque engines. The F350 vans in my company's fleet run 55/80!!

Dtv211

Who cares about comfort, mpg is all that matters!!!!!!

Vik888

HAHAHAHAHAHAHA. If you care about mpg, you wouldn't own a E320. There is a Prius with your name written on it somewhere.

Mercedes makes luxury vehicles. That is their primary goal, not mpg.

LaicepsYdobon

There are two reason for this; to introduce understeer in the car to make it safer for ham-fisted drivers and also to compensate for the weight of the engine in the front.

westcott

Although you may be right, I am still a little skeptical. One, if you were trying to compensate for the weight of the engine, why would you lower the air pressure of the front tires? The E550 has a 51/49 weight ratio. This does not jive with weight compensation. Two, I am not conviced about torque compensation. The E550 has traction control and stability control. That pretty much limits traction loss.

I guess I could buy the safety aspect by lowering the tire pressure up front but isn't there better ways of implementing understeer? Running low tire pressures, as others have stated, is not usually good for mpg or tire wear. Seems more like a last minute engineering fix than a well thought out understeer solution by Mercedes. This also seems curious, if it is indeed the case.

P.S. How many of you have had someone else fill your tires and when you check them (imagine how many drivers don't), they are all at the same 35psi or more, all the way around? Seems like the bone heads at the tire store or the service station would know where to find the correct air pressures for your vehicle by now. This obviously would negate any attempts by Mercedes to control understeer in their vehicles.

KL2DC

Well factory air pressure recommendation settings are factored in when they are figuring out the desired suspension geometry. All manufacturers lean towards understeer. Even BMWs with their 50/50 distribution have lower front air pressure settings.

I always pump up the front air pressures a couple of notches closer to the rears in all my cars to (hopefully) induce a more neutral stance - not that I push the car hard enough in daily driving to appreciate the difference

mcleantmw

I use 32 lbs on all four tires, including the brand new Michelins I just installed two weeks ago. I find no significant difference in handling or comfort with increasing the air in the front from the factory recommendation of 28 lbs. And, I've had Goodyear store folks tell me that keeping the air in a vehicle a little higher, even 35 lbs or so, increases the wear life of your tires. You all might recall during the presidental campaign that Obama even said the people could get more gas mileage, thus saving energy costs, if people would inflate their tires to a higher lbs setting. Finally, for those that say Mercedes owners should not worry about saving costs on the operation of their vehicles, whether mileage, repair costs, tire wear, etc, how many millionaires take that attitude............not many or they wouldn't be millionaires.

amdeutsch

Higher weight due to engine in the front = lower pressure in the front.



You walked in on that one eyes wide open.

LaicepsYdobon

No seriously hear me out. Because there is extra weight in the front, the engine, you want to decrease the pressure in the tires to give you a more smoother ride. Imagine a beach ball. If you fill it up all the way with air and sit on it and bounce around its going to be uncomfortable for you. If you let some air out and bounce around the shocks will feel more subtle. The same with the car; if you put too much air in the front tires and hit a pot hole it will be more uncomfortable because there is more tendency for the heavy engine to bounce on the hard tires. Take some air out and more energy will be absorbed and less bouncing around. It does make sense...

mcleantmw

By the way, I used to discount the use of nitrogen in tires instead of air......thought it was just some hype. But when I had my new Michelins installed recently at my MB Dealer, my service rep said that nitrogen keeps a constant pressure in the tires regardless of the outside temperature or heat from the tire running on the pavement.........air pressure in the tires will fluctuate due to temperature changes. So, since they offered the nitrogen, I had them use it and I now see the advantage over just using air to inflate tires.

LaicepsYdobon

The last time I was at my dealership they gave me a pamphlet about this. It also mentioned that leakage will not be an issue since the nitrogen molecules are larger then air molecules.

Keep us posted on how this is working out for you. I was thinking about trying this out but it makes me a little uncomfortable that I can't just fill my tires with air whenever I need too.

westcott

Last night on the evening news I saw a swarm of police surround your house. You could clearly hear over the bullhorn.

"PUT DOWN THE AIR HOSE AND MOVE AWAY FROM THE CAR!!!!"

amdeutsch

I know what you are attempting to say. But reread your other quote. If you are now arguing this way then you will wear out the front tires prematurely. Also, if you look at your pressure plague it tells you to increase pressure for load and/or sustained high speed driving.