spclagent7

I ran a search here on MBWorld to find what correct tire pressure should be. It was not pretty. There was a thread in this forum back in 2006 where fellow members got downright nasty. Someone caught in the middle was a forum moderator as well.

I never found the "correct" answer.

I inflated my tires for the first time myself today. I got confused. Should I follow the max PSI stated on the tire sidewall? Or do I follow what was stated in the driver doorsill? Tire sidewall said 51 PSI. Doorsill said 28 PSI front and 30 PSI rear at driving speeds less than 100 mph.

What is right?

After looking all over the Internet, and asking tire people today, the consensus is: follow the car manufacturer's recommended tire pressure, NOT what is printed on the tire sidewall (or any formula based on the tire sidewall, e.g. 51 PSI +/- 10%). This assumes that you are running OE tires. If you're running non-OE.... All I can say is good luck finding the "correct" pressure!

I wanted to post what I finally found. Because previous threads were inconclusive. In retrospect they were funny to read however because people were going crazy on the boards on this topic. Perhaps I shouldn't have laughed so much, as it can be a very serious topic.

All the best to everyone.

pinebaron

The link below may help answer a few of your questions about tire pressures. I follow vehicle manufacturer's reccomended tire pressures; note tire pressures are notably higher if you plan to drive consistently at speeds in excess of 100mph; unlikely but possible.

http://www.tirerack.com/tires/tirete...jsp?techid=147

SPNJHockey

Hey, Exit 4, check that link again. ;-)

pinebaron

Thanks Exit 16E; corrected.

Regards,

Exit 4

vettdvr

I run 32 psi all 4 after buying 2 sets at 15,000 due to cupping. I tried running the door jam #'s but given the uneven wear I went to 32 psi. My corvette uses the same size tire as the E500 and I have been running 32 in those tires for the last 9 years with great results. Much lower than the maximum but over the 100 mph psi's reco by MB.

Not unsafe because still within spec, but does give my new Michelin Pilot Sports better life. Currently after 5,000 miles on the new Mich's I can't see any abnormal wear patterns.

SO for me 32 psi. Some might want softer,, others harder,, but your driving style, tire wear and speeds will determine your "custom" pressure.

Davel

I use the recommendation posted on the inside of the gas cap door, which i believe is 29 front 32 rear, still on original tires at 42K miles and they have worn evenly except for the outside edges from cornering, i rotate every 15K miles front to rear crossed...

Barry45RPM

The tire wall pressure is a Maximum inflation LIMIT before the tires are likely to fail, not what will give you the best ride/performance when those tires are installed on a particular make/model of car. The tire manufacturer has no idea what cars those tires will end up on, so it can only guide someone what pressures to avoid. The car's manufacturer specified a certain tire be installed on a car model based on certain car & tire criteria, including, inflation pressure.

Inflate the tires within a couple of pounds of the gas door reccomended tire pressure specs.

Things like temperature, altitude, vehicle load & speed effect what pressure should be actually used.

jmorgis

I do 35psi rear and 33 front.

I prefer a stiffer / firmer ride.

JM

cyclrder

in 28 degree weather.. my tires are 28 front 34 rear... that would be door spec (or close to it).. but in 44 degrees... those same readings cold will be 31 and 38.. so pay attention to your ambient temp. it will give you a larger swing than you might expect.

remember, those are cold pressures used for baseline... if MB says to use 29/36 (I think that is what is in my doorsill)... what they are really looking for is about 33 and 40 at running temperature on the highway.

in my opinion.. the car feels and handles the best with the front tires running @ 33 front and 39 rear (heated up temp).... so however you get there is your decision


never fill a tire to the pressure on the sidewall...

lkchris

What's the problem with following the instructions of the sticker inside the fuel filler door? NOBODY ANYWHERE has better suggestions.

LAZARU5

When I first got the E500 4Matic nearly three years ago I ran the recommended tire pressure of 29 front and 34 rear. After 5000 miles the middle of the rear tires appeared to be worn more than the fronts. My understanding was that this was probably because the rear tires were over-inflated.

I started running 32 psi on all four corners and noticed three differences; more even wear on the rear tires, less wandering on the road with higher front tire pressure, and a 2 mpg increase in gas mileage. I now have 27,500 miles on my second set of tires and I expect to get at lease 45,000 miles from the Conti Extreme Contact directional tires. I rotate the tires every 5000 miles.

LaicepsYdobon

I second what Barry45RPM said. The tire sidewall said 51 PSI because that is the maximum the tire can be inflated to according to the manufacturer's recommendations. Follow what MB recommends on the doorsill. 51 PSI will give you a very harsh ride. Also be very careful when blowing tires up; if you over do it and the tire blows the force is so strong is can kill you. You can look in the cars manual or talk to your service adviser to help clean things up.

E500Newbee

Since everyone is on this tire pressure issue. What do you guys think about the tire fill-up with the Nitrogen my dealer is offering? Here is what they claimed:

Why Nitrogen?
·

Nitrogen inflated tires do not age as quickly as air inflated tires.
·

Nitrogen inflated tires minimize blowouts.
·

Nitrogen inflated tires improve vehicle handling through proper inflation.
·

Nitrogen is an inert, non-combustible and non-flammable gas.
·

Nitrogen is a stable gas providing more constant pressure, working better with tire pressure monitoring systems.
·

Using nitrogen instead of compressed air has distinct advantages, which lead to immediate benefits for the vehicle owner.
·

Compatible with normal air inflation if emergency filling is needed.
·

It has more mass, so it migrates through the tire three to four times slower. The result: Tires hold their Pressure longer.
·

. It runs about 20% cooler. Less heat results in less tire degradation.
·

It drastically reduces oxidation on the rim and inner-liner (nitrogen systems almost totally eliminate oxygen—the cause of oxidation).
·

It is environmentally safe.

Who Uses Nitrogen?
·

NASCAR - NASCAR teams use nitrogen because it allows them to more accurately predict tire pressure fluctuation.
·

Commercial Airlines – The Federal Aviation Administration requires nitrogen in aircraft tires because it reduces the potential for water vapor freezing at high altitudes.
·

Beck Imports of the Carolinas.

LaicepsYdobon

I've heard that you should not mix nitrogen with air. I don't know which statement is right; I'm not a chemist. Perhaps someone with a bit more knowledge then my high school chemistry classes could shed some light on this. They were offering this at my dealership also but not too many people were going for it.

cyclerider

About 78% of the air you breathe is nitrogen. 21% is oxygen and 1% is other gases. I think it's OK to put it in your tires.

pinebaron

By reducing the percentage of oxygen, water vapor and other gases in your tires from 22% to 7% or lower, your tires will maintain proper pressure longer than if you use “plain old air.” For example, with 95% nitrogen in your tires, they retain optimal pressure three to four times longer

Courtsey: http://www.getnitrogen.org/why/index.php

211E350Black

look on the inside of your gas door

vettdvr

Which is exactly why I run 32 all 4.

Oxygen with air. It comes that way. I don't worry about humidity in the tires. The outsides see more water than the inside and I check pressure. I would never put N2 in my tires unless I was trying for world speed record.

I think N2 in tires is just smoke and Mirrors for more $$.

But then everyone has an opionon. O2 + N2 => O2 & N2 with does not react

Barry45RPM

Just out of curiosity, what do they charge to fill a tire or 4 tires with nitrogen? Also, do they change the valve or just the valve cap to signal Nitrogen?

LaicepsYdobon

At my dealership (MB Manhattan) the nitrogen for you tires was free. I'm not sure what they do with the valve/valve cap of your tire. I'm not even sure if they need to reconfigure the Tire Pressure Monitoring system of the car.

Taylor-Made'90

I run my tires at 28/32 cold..... I've gotten very good wear too......

Barry45RPM

I just thought that a Nitrogen filled tire might be marked by a different color stem or cap... I don't know why.

Jon2007E63P30

The point about the water content for the air inside the tires is that it has a very large effect on the pressure in the tire as it changes temperature. If you get too much water inside the tire, it can condense out at low temperatures and even cause imbalance. This is rare. Get rid of the H2O and normal air mix will work damn near the same as pure N2.

Personally, a good shop air pump does a fairly good job of getting our the water. I don't use the air pumps that sit at one end of the gas station.

mtnbenzer

I read somewhere that MB wants to make sure the car will under steer in an emergency so that dictates their pressure recommendations. They want to error on the side of an inexperienced driver vs. having a hacker trying to catch the tail coming around. That is why they recommend higher pressure in rear tires. I have run 36 all around in my last and present E-Class as I drive out west and often off the interstates so I want a firmer ride and handling. Had no problems with unusual tire wear on my previous E-430 4-matic.

E500Newbee

At my dealership they are running special for $39.95. Regular is $49.95. But my thing is, the nitrogen eventually going out. Just a 2 or 4 psi, than you have to return to the dealership for that 2 or 4 psi and pay $49.95???