When you own two identical cars you notice minor things...

One 2006 CDI, production date June 2005, has tire pressure recommendations of 28 PSI front, 30 PSI rear.

The other 2006 CDI, production date May 2006, has tire pressure recommendations of 28 PSI front, 33 PSI rear.

Not a big deal...but I guess the engineers revised their thinking over the course of a year.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

The engineers were asked to adjust the rear tire pressures to accommodate the weight of an un laden swallow in the boot. One of your sedans is specified for an African swallow and the other for the slightly heavier European swallow.

Next important question is: What is your favorite color

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

I have always wondered why MB tended to specify lower pressure for the front tires. Most other makes that I deal with have it the other way around. Which would tend to make sense, since the front end tends to be heavier than the rear, at least on an average day.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

There are more important things in life than questioning about 3lbs of tire pressure. I would be more worry if it had been rocket pressure.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

I would guess that the higher pressure is meant to prolong the tread life on the rear tires. At the recommended pressure on my "97 E the rear tires wear on the inside at a ridiculous rate. I have had the alignment checked and new shocks installed, but the biggest help was raising the pressure to 30 PSI. I was told by a tech at an indi. that specializes in Mercedes, that you are lucky if you get more than 35K on a set of tires on a Mercedes because of the rear suspension. I went through a set in about that distance using the pressure on the gas door. I am hoping to do better now that I use 30 PSI all around. The rear wear is noticeably better.

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'97 E 300 D

Interesting. Rear end sticks better, tires wear. I am OK . Rotate often is the key to tire longevity .

Almost all manufacturers advise softer than optimal tires pressures as this gives a slightly better ride .

Chalking or striping your tires will show you the specific best pressure for any particular vehicle regardless of tires, brands, driving habits, loading and so on .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

To me it is simple. Rear with a load needs more tire pressure for load carrying capacity.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

They may have come with tires of different load ratings. My Jeep asks for 35psi but switching to larger tires with a higher rating, we run around 42-44.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

And the logic behind that is....?

Where I went to school, larger tires require less pressure, not more.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

Spot on, on my cars the two pressures listed are called out as normal load, max payload, with the higher pressure at max. Given that cars are provided two weight specs, curb, and gross, the various tire pressures are related to accommodate those two weight differences

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

If load was the determining factor, there is no reason for the front tire pressure in a passenger car to be lower than the rear in "normal" payload configurations.
As far a curb weight goes, when does a manned vehicle ever operate at that weight? (Okay, maybe it you have an near-empty fuel tank and a horse jockey for a driver.)

The majority of the passenger cars that I deal with specify higher pressure in the front tires, if there is a difference.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

Do you have front drive cars? My comments were mainly in reference to rwd cars.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I agree with tangofox that larger tires should have lower pressure. Some folks see the max pressure value on the tire and mistakenly believe that that is a recommendation, rather than the do not exceed pressure. A few years back I had a new set of tires installed on a Bronco. When I drove home I was alarmed by how twitchy the truck was. I thought I had made a major mistake in the tires I had selected. I checked the tire pressure and found they all had 45 psi in them. I dropped them all to 30, and it drove like a new truck.

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'97 E 300 D

Some time ago, I did some work on a Toyota van belonging to one of my neighbors. I noticed that all four tires were showing significant excessive wear in the center of the tread. Checked the tire pressure and found the tires to be severely overinflated. Brought the matter to the owner's attention; he explained that he was using the pressure listed on the sidewall, because his father had taught him to do it that way.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.