Mercedes-Benz Forum banner

1 - 11 of 11 Posts

·
Registered
99 E300TD/02 SLK230K
Joined
·
152 Posts
Discussion Starter #1
Hey guys, on an 02 SLK230 with the OEM tires (Dunlops 16 in front, 17 in rear) what tire pressure should I use for best mpg? I was thinking 32psi, but would that be too much for the summer time? Also I have some occasional spirited driving in there.

Thanks,
Kishan
 

·
Registered
2002 SLK 32 AMG, bone stock. 1987 190E 2.3-16 valve (destroyed). 2005 E320 new toy.
Joined
·
14,926 Posts
Hey guys, on an 02 SLK230 with the OEM tires (Dunlops 16 in front, 17 in rear)
That would not be the stock set up.
Stock is 205x55/16 tires in front and 225x50/16 in back, or 225x45/17 in front and 245x40/17 in back. In any event the Mercedes recommended tire pressure is on the inside of the fuel door. With the 17" tires the pressure is 32 psi in front and 35 psi in back. If you want better mileage and handling you want more pressure at least in the front.
The normal suggestion is 35 to 37 psi all around.
 

·
BenzWorld R170 SLK Host
2002 SLK32 AMG
Joined
·
2,652 Posts
I agree.

Start with all 4 tires at around 35psi. Lower the pressure a bit if the ride is too harsh or raise it a bit for more spirited driving. However don't ever let it drop below the recommended 30psi front 33psi rear or you will notice a decrease in tire life.
 

·
Registered
SLK32, ML430
Joined
·
6,349 Posts
RE: I agree.

Brian_R170 - 4/8/2005 12:10 AM

Start with all 4 tires at around 35psi. Lower the pressure a bit if the ride is too harsh or raise it a bit for more spirited driving. However don't ever let it drop below the recommended 30psi front 33psi rear or you will notice a decrease in tire life.
Maybe I just have a higher tolerance than others but no amount of tire pressure is going to make the SLK's ride too harsh. Too much pressure will decrease your contact patch and tread life though.
 

·
Registered
99 E300TD/02 SLK230K
Joined
·
152 Posts
Discussion Starter #5
I was wrong about the 16's and 17's apparently. They look bigger in the back though. I'm going to try 33/35. Will let you guys know.

Thanks for all the help!
 

·
Registered
2002 SLK 32 AMG, bone stock. 1987 190E 2.3-16 valve (destroyed). 2005 E320 new toy.
Joined
·
14,926 Posts
RE: I agree.

Too much pressure will decrease your contact patch and tread life though.
That is quite true ... The car builders, (in this case Mercedes) normally set the tire pressures to insure a good ride, and also to help insure a certain amount of understeer.
The understeer situation where a car tends to go straight, is considered to be safer then an over steer condition where the rear end tends to come around on you.
If you were to increase the tire pressure in front to let's say 35 to 37 psi you gain somewhat better handling, slightly better tire wear, and slightly better mileage through lower rolling resistance.
I have run much higher pressures as an experiment on the track, and at 40 psi the car feels like it's "dancing on eggs". It feels almost twitchy, especially in front. It turns OK, but your not really sure if it's going to turn, and when it is in the turn, you're not really sure if it's going to stop turning. Very uncomfortable feeling. Tire wear was accelerated through the center of the tire tread.
I think that a lot of guys have gone to the slightly higher pressures and I haven't heard any complaints. I certainly would like to know if there have been problems, and what they were...[:I]
 

·
Registered
SLK32, ML430
Joined
·
6,349 Posts
RE: I agree.

Bruce R. - 4/8/2005 9:53 AM

That is quite true ... The car builders, (in this case Mercedes) normally set the tire pressures to insure a good ride, and also to help insure a certain amount of understeer.
The understeer situation where a car tends to go straight, is considered to be safer then an over steer condition where the rear end tends to come around on you.
[:I]
The thought that understeer is safer drives me crazy (although I will concede the point that it may be safer for a majority of the drivers). I have a chance of recovering, correcting, or avoiding a problem with oversteer. With understeer pretty much all you can do is hang on for the ride.
 

·
Registered
2002 SLK 32 AMG, bone stock. 1987 190E 2.3-16 valve (destroyed). 2005 E320 new toy.
Joined
·
14,926 Posts
A couple of thoughts on understeer vs. oversteer .....

Right off the bat, this is only an opinion, so take it for what it's worth. (Not much, I know that. [;)])
From what I've seen and observed first hand, most drivers have a very hard time recovering from a good dose of oversteer. What usually happens is that you lose the rear, you correct, the rear end "bites" again, and then takes off in the other direction. If the car doesn't spin, and the rear "bites" again, then you spin in the first direction. The car just swings back and forth until you are lucky enough to stop in the clear, or hit something sideways, or backwards.
With oversteer, if you think enough to release the brakes or the ABS works as it should you stand a small chance of missing what's in front of you. Of course the chances are pretty good that you'll hit the tree that you've been watching, and hopeing that you going to miss. [:p] [xx(]
I don't like the heavy understeer that most cars are saddled with either, but I understand why (or at least I think I do).
You might recall a few years ago when Porsche allowed slight oversteer in their production cars, they found an awful lot of them backed into trees and guardrails. I think air bags work better when you hit things in the "right direction" too....[:eek:)]
Like I said, just a few thoughts for what it's worth...[:I]
 

·
Registered
2001 SLK 230
Joined
·
493 Posts
God help me, I agree with Bruce for a change! [:D]

I have been running my tires at 40 psi all around for about a month, and I'm going to try dropping back to 37 psi and see how I like that. The ride is truly twice as rough (to me) at 40 psi than it is at the recommended pressures. The cd player even skips sometimes. The handling is a little squirrely, although I seem to be used to it now. My wheels are the stock 16" and my tires are some playa brand "Heritage" that carmax stuck on the car, although the size is correct.
 

·
Registered
2002 SLK 32 AMG, bone stock. 1987 190E 2.3-16 valve (destroyed). 2005 E320 new toy.
Joined
·
14,926 Posts
God help me, I agree with Bruce for a change!
Hey don't feel bad, accidents happen.... [:D][:p]
 

·
Registered
Joined
·
290 Posts
RE: I agree.

430 - 4/8/2005 8:17 AM
Maybe I just have a higher tolerance than others but no amount of tire pressure is going to make the SLK's ride too harsh.
Oh, yeah? Driving on Nu Joisey roads will cure you of that bravado in a day or two.

About built-in understeer, it is based on two assumptions of John Q Driver. One, people don't provide sufficient steering input and tend to overshoot curves for their speed (and suddenly feel they are going too fast for the curve). Two, their first impulse when they see themselves overshooting is to lift of the gas pedal or stomp on the brakes.

When they do that, the weight shifts to front and their steering input becomes more effective to get them through the curve.

If they do that on a oversteering car, the back will suddenly lose some traction with the abrupt input and will tend to spin the car out (this is what happened to all those Porsche drivers that wrapped themselves around a tree taking a curve fast).
 
1 - 11 of 11 Posts
Top