not-front-rule

Tire Pressure

Welcome to the Mercedes-Benz Club of America Forums
Here, you'll find members en masse who can talk, guide, answer or listen to your Mercedes-Benz related questions and comments. Participation in the forums is free to Club members. If you're a guest of this site, you'll have access to our read-only discussions. Like what you see? Join the Club to get full Q&A privileges. If this is your first visit, be sure to check out our FAQ page.  To start viewing messages, select the forum that you want to visit from the selection below.

Forum Jump

26 replies [Last post]
Former Member
ALUEB's picture
Offline
Joined: July 8th, 2002

Posts:
2041

Vehicles
1979 450SLC

The mfg specs for tire pressure for my car a 99 C290 is 28PSI front and 32PSI rear. I read a long time ago, that increasing tire pressure in the front, as compared to the rear will induce oversteer and decreasing tire pressure in the front as compared to the rear will induce understeer. What the real story.

To me it would make more sense to increase the tire pressure in the front compared to the rear of the car because of the additional weight the car is carrying in the front, IE, engine transmission etc. :confused:

Share this
Administrator
Alex's picture
Long Island City, NY
Offline
Joined: January 12th, 2004

Posts:
3584

Vehicles
2004 Sprinter
2004 CL500
2004 C320
1981 300TD
Re: Tire Pressure

Al,

The specified tire pressure already takes into consideration the optimum weight distribution, averaging in the driver who's always there, plus passangers, who might be there or not.

I've found that increasing the tire pressure by a few pounds in both the front and rear tires improves handling, gas mileage and tire life. Of course, it also increases the feel of the bumps.

You might start with 30' in front and 32' in rear and see how that feels, then experiment by increasing it from there by one pound at at time, not exceeding 36 pounds.

It might also be worth mentioning that an accurate tire gage is called for, as is awareness of outside air temperature when filling tires. A 10 degrees F change in air temperature affects the air pressure reading in tires. Also, the tire pressure will read significantly higher when the tires are warm, as they are after a ride.

So I make it a practice to only measure the tire pressure in the morning, when the tires are cold.

The tire monitoring system built into the CL, which is pretty accurate, shows the air pressure to be changing in the tires all the time. It's low in the beginning, rises as the tires heat up, and not equally at that, then lowers as they cool off.

A friend, who's Lexus dealer puts helium or nitrogen into his tires, instead of air, says that the tire pressure stays more constant than with air, but I have no experience with it, so can't vouch for that.

__________________

Alex Rosner
Member, NYC-Long Island Section
Member, MBCA Technology Committee

Former Member
ALUEB's picture
Offline
Joined: July 8th, 2002

Posts:
2041

Vehicles
1979 450SLC
Re: Tire Pressure

Alex

Thanks for the information, My son filled my tires this morning as I have one that has a slow leak, I've had it checked twice, had the valve replaced and still the tire looses 10 psi or so about every two weeks, faster in the winter I think corrosion inside the rim might be the problem. For the price of a Mercedes rim I can buy 4 new rims at tire rack so I am going wait and see. Anyway, I had him put in 32 psi in the front and rear, going to see how that combo works.:D

Member
ggoodman's picture
Kent, OH
Offline
Joined: March 15th, 1991

Posts:
193

Vehicles
2012 C300 4MATIC
2003 C230
1964 190c
Re: Tire Pressure

You are correct that increasing front pressure will increase oversteer/reduce understeer. If you LOWER the rear pressure relative to the front that will LOOSEN the back end--you can do this by either lowering the rear pressure or raising the fronts. (I would not recommend lowering the rear). Besides weight distribution etc as Alex mentioned, the factory tire pressures are designed to create gentle understeer as that is safer for most folks for street use. I generally run equal front and rear pressures on my cars (W201 190 and W203 C230). A good way to check how it feels is to use an expressway ramp--I think you will find with equal pressures the car sticks better and also holds the line without steering corrections better than factory pressures. 32 psi is a good starting point--I usually run 32-35 psi. Just experiment until you get the balance of ride, handling, & tire wear that you like. Hope this helps and wasn't too long-winded :)

__________________

Member
vince's picture
Chesapeake, VA
Offline
Joined: September 1st, 1973

Posts:
1167

Vehicles
2014 ML350
1999 E430
Re: Tire Pressure

I use 32F, 36R on the 1995 C280.

I use 37 all around on my 2000 C280 Sport. My son uses the same on his 1999 C43.

__________________

Vincent Canepa Member since 1973 1999 E430, Smoke Silver w/Parchment full leather  2014 ML350 4Matic Diamond Silver w/Auburn Brown-Black leather

Member
jrct9454's picture
Vancouver, WA
Offline
Joined: August 30th, 1994

Posts:
413

Vehicles
2010 GLK350 4MATIC
Re: Tire Pressure

Tire pressures are like oil change intervals - almost a religious question....

That said, over the years I've tended to run our Mercedes sedans at 30-32 psi all around. The factory recommendations are there basically to insure nice, safe understeer....not really an issue in the era of stability control, and really never an issue in anything approaching normal driving.

Anything over 34-35 psi in a sedan is going to cost you some ride quality; once you get too high [over 40 psi], you're asking for tire wear problems. That leaves a pretty broad range [28-36 psi] that is a tradeoff between ride quality and handling. Do what makes you feel comfortable within that range.

I should add that carrying a full load really does require getting the pressures up into the 33-36 psi range, assuming you have the correct sized tires with the appropriate speed rating. Light loads mean you can do anything you want within reason.

Finally, if you have wheel problems, I can say that we bought 5 new Rial wheels from Tire Rack for our '08 C300 that were the exact spec as the OEM wheels, even looked the same, for the princely sum of $99 each. These are German-made and TUV approved. There are lots of good wheel choices out there that are safe and not going to empty your wallet.

__________________

John Robison

Vancouver WA    '10 GLK350

Former Member
ALUEB's picture
Offline
Joined: July 8th, 2002

Posts:
2041

Vehicles
1979 450SLC
Re: Tire Pressure

The 32 psi from and rear seems to work well, I haven't done any hard driving but around town the ride doesn't seem to be effected by the higher pressure in front.

On the subject of new wheels, I've seen several wheels on Tire Rack that would look good on my car prices range from $100 to $113 each wheel. Not bad considering what one Mercedes wheels cost. I think in the spring I'll invest in some new wheels for my C280. Wave

Member
David Brittain's picture
Folsom, CA
Offline
Joined: March 29th, 2006

Posts:
914

Vehicles
2000 SL500
2009 C300 4MATIC
Re: Tire Pressure

Speaking of tire pressure, may I stray a little from the issue being discussed here and ask if anyone is familiar with the new trend of putting nitrogen in tires instead of air?

I was at my favorite local tire shop a couple of weeks ago getting the wheel bearings packed on my 944 and a balancing job and the owner told me they had begun offering nitrogen for tires. He said nitrogen filled tires provided a slight improvement in mileage and longer tire life in addition to eliminating the fluctuation in pressure as a result of extreme temperature changes.

Anyone got any experience in this area and ready to offer opinions? :confused: My tire man charges $40 for filling four tires with nitrogen.

Dave

__________________

David Brittain Folsom CA Sacramento Section

Member
jrct9454's picture
Vancouver, WA
Offline
Joined: August 30th, 1994

Posts:
413

Vehicles
2010 GLK350 4MATIC
Re: Tire Pressure

Well, it's not worth $40, which is ridiculous. Yes, there is one main advantage - nitrogen doesn't vary as much as temps go up and down as compressed air, and there may be less pressure lost over time for the usual reasons [flexing, etc.]. The only mileage improvement would come from less pressure being lost, and that would be so small as to be almost impossible to measure for most people - 1-3% maybe?

Costco has used nitrogen at their tire shops for a number of years now [look for their green valve caps if you want to find cars with tires from Costco].

In other words, it's a good thing, but hardly worth $40....I might be willing to pay $1 a tire, or something like that, but otherwise, it makes no economic sense.

__________________

John Robison

Vancouver WA    '10 GLK350

Member
David Brittain's picture
Folsom, CA
Offline
Joined: March 29th, 2006

Posts:
914

Vehicles
2000 SL500
2009 C300 4MATIC
Re: Tire Pressure

Thanks John. Yes, $40 is a rather pricey for filling your tires. The whole thing may turn out to be one of those short-lived fads. Personally, I think I'll pass on it.

I check my tire pressures about once a month and try to keep them properly inflated at all times anyway. I think I've milk about as much as one can out of tires.

__________________

David Brittain Folsom CA Sacramento Section

Former Member
ALUEB's picture
Offline
Joined: July 8th, 2002

Posts:
2041

Vehicles
1979 450SLC
Re: Tire Pressure

I have my own air compressor, so I think I keep on using that instead of paying $40 for something that is not really proven to provide a lot of benefits. Especially with the leaking wheels I have. ;)

Content Manager
editorgary's picture
Los Altos, CA
Offline
Joined: January 11th, 2008

Posts:
2173

Vehicles
2005 C55 AMG
Re: Tire Pressure

The discussion about the advantages of nitrogen to fill tires has raged on several other lists in which I participate. Here's what I believe is more or less agreed on.
l. Comparing pure nitrogen to compressed atmospheric air, there is almost no difference in the compression/expansion factors (our atmosphere is 78 percent nitrogen), well below what any amateur driver would be able to perceive.
2. The amount of moisture in the gas being pumped into the tire makes considerably more difference in the expansion and contraction factor.
3. Because nitrogen (at the track or in the tire supply store) is already in a tank, it has little moisture compared to tire pumps or other sources of air, and consequently has a lower expansion/contraction factor.
4. Using a tank of compressed air produced from a compressor with an attached dehumidifier is almost as good as nitrogen.
5. There's no substitute for getting your tire pressures correct, and checking and adjusting them weekly on a daily driver, and after every session at a track day, regardless of whether you use dry compressed air, nitrogen, or a bicycle pump.
Gary

__________________

Gary Anderson Editor, The Star
2005 C55 AMG
Member, San Francisco Bay Area Section
Secretary, MBCA Educational Foundation
Vintage racing driver, track driving instructor

Former Member
ALUEB's picture
Offline
Joined: July 8th, 2002

Posts:
2041

Vehicles
1979 450SLC
Re: Tire Pressure

jrct9454;183357 wrote:
Tire pressures are like oil change intervals - almost a religious question....

That said, over the years I've tended to run our Mercedes sedans at 30-32 psi all around. The factory recommendations are there basically to insure nice, safe understeer....not really an issue in the era of stability control, and really never an issue in anything approaching normal driving.

Anything over 34-35 psi in a sedan is going to cost you some ride quality; once you get too high [over 40 psi], you're asking for tire wear problems. That leaves a pretty broad range [28-36 psi] that is a tradeoff between ride quality and handling. Do what makes you feel comfortable within that range.

I should add that carrying a full load really does require getting the pressures up into the 33-36 psi range, assuming you have the correct sized tires with the appropriate speed rating. Light loads mean you can do anything you want within reason.

Finally, if you have wheel problems, I can say that we bought 5 new Rial wheels from Tire Rack for our '08 C300 that were the exact spec as the OEM wheels, even looked the same, for the princely sum of $99 each. These are German-made and TUV approved. There are lots of good wheel choices out there that are safe and not going to empty your wallet.
Tire Rack has ASA 15' and 16' 8 hole wheels which look oem for my C280 at $99 either size. I am now wondering what effect would 16 inch tires have on the handle, ride, economy on my C280 (15' are standard). Thanks:confused:

Former Member
ALUEB's picture
Offline
Joined: July 8th, 2002

Posts:
2041

Vehicles
1979 450SLC
Re: Tire Pressure

editorgary;183726 wrote:
The discussion about the advantages of nitrogen to fill tires has raged on several other lists in which I participate. Here's what I believe is more or less agreed on.
l. Comparing pure nitrogen to compressed atmospheric air, there is almost no difference in the compression/expansion factors (our atmosphere is 78 percent nitrogen), well below what any amateur driver would be able to perceive.
2. The amount of moisture in the gas being pumped into the tire makes considerably more difference in the expansion and contraction factor.
3. Because nitrogen (at the track or in the tire supply store) is already in a tank, it has little moisture compared to tire pumps or other sources of air, and consequently has a lower expansion/contraction factor.
4. Using a tank of compressed air produced from a compressor with an attached dehumidifier is almost as good as nitrogen.
5. There's no substitute for getting your tire pressures correct, and checking and adjusting them weekly on a daily driver, and after every session at a track day, regardless of whether you use dry compressed air, nitrogen, or a bicycle pump.
Gary

I agree completely with your last paragraph. It is especially important to check them regularly this time of the year.:D

Administrator
Alex's picture
Long Island City, NY
Offline
Joined: January 12th, 2004

Posts:
3584

Vehicles
2004 Sprinter
2004 CL500
2004 C320
1981 300TD
Re: Tire Pressure

ALUEB;183819 wrote:
Tire Rack has ASA 15' and 16' 8 hole wheels which look oem for my C280 at $99 either size. I am now wondering what effect would 16 inch tires have on the handle, ride, economy on my C280 (15' are standard). Thanks:confused:

The benefit of using the larger rim with less rubber will be smarter looks and slightly better handling on turns. The disadvantage will be more sliding around in ice and snow, a slightly stiffer ride and greater susceptibility to curb rash.

__________________

Alex Rosner
Member, NYC-Long Island Section
Member, MBCA Technology Committee

Member
jrct9454's picture
Vancouver, WA
Offline
Joined: August 30th, 1994

Posts:
413

Vehicles
2010 GLK350 4MATIC
Re: Tire Pressure

Al:

Personally, I'd stick with the 15s for your car - less expensive tires, better ride....all marginal, of course, as the differences will be small in any case.

Compare 195/65x15s with 205/55x16s....up to you.

__________________

John Robison

Vancouver WA    '10 GLK350

Content Manager
editorgary's picture
Los Altos, CA
Offline
Joined: January 11th, 2008

Posts:
2173

Vehicles
2005 C55 AMG
Re: Tire Pressure

15s with a 65 profile tire (more air and rubber, less wheel) will give you the more comfortable ride. 16s with the 55 profile (less air and rubber, more wheel) will give you better handling because they turn in more easily and have less sideways displacement on corners, but they will transfer the shock of bumps more directly and you don't have as much rim and suspension protection when you e.g. hit a deep pothole. If you were buying a set of track tires and wheels, the 16s are definitely the right way to go, but for street use, most people prefer the 15s. (Incidentally, autocrossers generally opt for 15s, because they have less "unsprung mass" -- they weigh less -- so you get quicker pick-up which is important on short courses with tight turns.)
Bottom line: no definitive answer. Your selection depends on the kind of ride you want, the kind of driving you do, and the kind of performance you want.
Gary

__________________

Gary Anderson Editor, The Star
2005 C55 AMG
Member, San Francisco Bay Area Section
Secretary, MBCA Educational Foundation
Vintage racing driver, track driving instructor

Former Member
ALUEB's picture
Offline
Joined: July 8th, 2002

Posts:
2041

Vehicles
1979 450SLC
Re: Tire Pressure

Thanks for the replies on tire size. I checked out the difference in prices between the 15" and 16" and there is quite a difference on some brands. I'm just a day to day driver, no racing etc. So from what U all say I think I'll stay with the 15" and save a couple of bucks also. Thanks again for the advice.:)

Former Member
ALUEB's picture
Offline
Joined: July 8th, 2002

Posts:
2041

Vehicles
1979 450SLC
Re: Tire Pressure

jrct9454;183991 wrote:
Al:

Personally, I'd stick with the 15s for your car - less expensive tires, better ride....all marginal, of course, as the differences will be small in any case.

Compare 195/65x15s with 205/55x16s....up to you.

wouldn't the 205's give U a bigger footprint on the road?:)

Content Manager
editorgary's picture
Los Altos, CA
Offline
Joined: January 11th, 2008

Posts:
2173

Vehicles
2005 C55 AMG
Re: Tire Pressure

But more pricey, and if he's not tracking, would there be any advantage to having wider tires? Might reduce braking distance slightly, but at the expense of greater likelihood of hydroplaning in rain, wouldn't you think?
gary

__________________

Gary Anderson Editor, The Star
2005 C55 AMG
Member, San Francisco Bay Area Section
Secretary, MBCA Educational Foundation
Vintage racing driver, track driving instructor

Member
vince's picture
Chesapeake, VA
Offline
Joined: September 1st, 1973

Posts:
1167

Vehicles
2014 ML350
1999 E430
Re: Tire Pressure

195/65x15 were stock with 15" wheels. 205/55x16 were stock with the Sport Package. I have a normal and a Sport Package W202. I think the real difference between the cars comes from the shocks, springs and sway bars, which were very aggressive on the W202 Sport Package, and the fact that the 16" wheels are 1/2" wider (7" vs. 6 1/2"). I have been running another option no one has mentioned on my "normal" model - 205/60-15. Same rolling circumference, wider contact patch and better tire selection available. Many higher performance tires don't come in the 195/65 anymore.

__________________

Vincent Canepa Member since 1973 1999 E430, Smoke Silver w/Parchment full leather  2014 ML350 4Matic Diamond Silver w/Auburn Brown-Black leather

Former Member
ALUEB's picture
Offline
Joined: July 8th, 2002

Posts:
2041

Vehicles
1979 450SLC
Re: Tire Pressure

When I bought my car, it was a ceritfied preowned and 2 years old. It had 205/60-15 tires fitted. I am on my second set of tires and I bought 205/60/15's.

I checked on Tirerack.com and they show for my 99 C280 the 205/60-15's are the correct stock size.Wave I have the normal suspension.

Member
vince's picture
Chesapeake, VA
Offline
Joined: September 1st, 1973

Posts:
1167

Vehicles
2014 ML350
1999 E430
Re: Tire Pressure

You're right. I checked the Owners Manual for a 1999 C280 and the tire listed for the non-Sport is 205/60-15. The pre-face lift cars ('97 and earlier) list 195/65-15. The '98 and later also use 7 x 15 wheels vs. the '97 and earlier cars use 6.5 x 15.

__________________

Vincent Canepa Member since 1973 1999 E430, Smoke Silver w/Parchment full leather  2014 ML350 4Matic Diamond Silver w/Auburn Brown-Black leather

Former Member
ALUEB's picture
Offline
Joined: July 8th, 2002

Posts:
2041

Vehicles
1979 450SLC
Re: Tire Pressure

I also verified the size from the sticker on the door sill. 205/60R-15's Wave

Former Member
Jayhawk's picture
Lawrence, KS
Offline
Joined: August 30th, 2006

Posts:
2634

Vehicles
2000 S500
1970 280SL
Re: Tire Pressure
__________________

Gene Ramp

  • Midwest At Large
  • Content Manager
  • Content Editor
  • Forums Administrator
  • News Manager
  • Social Networks Manager
Member
syracusea's picture
Manhasset, NY
Offline
Joined: November 12th, 2009

Posts:
2087

Vehicles
2014 C300 4MATIC
2009 E350 4MATIC Wagon
2009 C300 4MATIC
Re: Tire Pressure

Is it better to check the tire presure in the morning (9am), before I drive or after a drive?
-Andrew

__________________

-Andrew 2009 NYC-Long Island Section

My Car: 2009 C300 4Matic Luxury Sedan

My Dads Car: 2014 C300 4Matic Luxury Sedan

My Moms car: 2009 E350 4Matic Station Wagon
              (soon to be my brothers car)
     

                   Keeping it in the family.

Former Member
Jayhawk's picture
Lawrence, KS
Offline
Joined: August 30th, 2006

Posts:
2634

Vehicles
2000 S500
1970 280SL
Re: Tire Pressure

syracusea;184484 wrote:
Is it better to check the tire presure in the morning (9am), before I drive or after a drive?
-Andrew

Always check your pressure BEFORE you drive, while the tires are cool.

__________________

Gene Ramp

  • Midwest At Large
  • Content Manager
  • Content Editor
  • Forums Administrator
  • News Manager
  • Social Networks Manager

Forum Jump

Share this