Hi..
I have 18" AMG monoblock wheels on my E420
with 18X8 in front and 18x9 in rear. The tires are Dunlop sp9000, 235/40/18 in front and 265/35/18 in the rear. Right now I put 28 psi for the front tires and 30 psi for the rear tires. What is the right pressure for this size of wheels and tires for this car???
thanks

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Donny
97 E420

Under normal circumstances, I would advocate keeping stock pressures but on that low a profile... What are your priorities? Looks or handling? Find the max cold PSI pressure (on tire's sidewall) and use that as the rear's pressure. Then use the same ratio as stock to determine what the front should be. That will give you the best handling option. ex. if stock ratio is 28/30 f/r then run 41/44 f/r You could also use the pressure specified for the E55. That car runs approx the same size wheel/tire and has a similar weight profile. According to the March 99 issue of Car&Driver, the inflation pressures for the E55 are 36/36. Hope this helps...Lee

Oh Donny,
How do you like the Dunlop 9000's? The 500E will be needing new rubber soon and I am always interested in owner experiences.

Lee

Thanks again Lee..
for the information.
The dunlop sp9000 does fine. It is quiet and soft, especially in the freeway you will like it. For acceleration, its not that perfect. My ESP light often comes on, especially in rainy days.The good year eagle F1 does better in wet road. I like sp9000 in cornering and high speed driving. But remember not in a wet days....:P. Overall it is a nice tires.But, I heard that Bridgestone SO-2 pole position is better than sp9000.
Well... it depends, Wet?? or Dry??:P


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Donny
97 E420

Hello Folks,

I need tire pressure help too.
I have a E320 99 with 19" wheels (stupid, I know, should have went 18")
Anyways, it's 245/35/19 (front), and 275/30/19 (rear); both are running on P-Zero.
The tires are great ! The tire pressure I am on 33 all the way around.

I have a fear of over pumping, that what happen to my previous car E39 528i and I popped it on the FWY ( I made a mistake of cold psi and hot psi haha...).

Thanks for the input,



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Happy Cruzing...

///Marco
-Opera Design Silver E320 99"
-245/275 P-Zero 19"
-Full Opera Design W210 E-clas body kit ( The First one in U.S.)
-Show car for Wheel Power Inc. (wheelpower.com)

Marco,
As long as you stay under Pirelli's specified "max cold psi" numbers then you should be okay. Some of the dangers are just par for the course when running that low a profile setup. I'm sure those 19" wheels were quite expensive so I would run pretty close to max psi numbers. The more pressure in the tire the more you protect the wheel. Higher pressure will hurt ride a bit but if ride were your priority then I doubt you would of bought the 19"'s. As I have said before...last thing at night go to the corner gas station (or wherever you have access to a compressor) and air the tires up to or even a slight bit over their cold psi numbers. Then drive home carefully. In the morning (when the car has been sitting many hours and is cold) you will get the most accurate pressure numbers. Adjust the tires down to the numbers you want. I'd recommend a 36/36 (E55) or something in that ballpark. Just keep the same pressure ratio as recommended under the fuel filler flap.

Hope this helps...Lee

PS Remember that if you adjust your pressure for a winter morning, it will be different from a summer afternoon. Check (in the morning) on a regular basis and adjust for seasonal changes.

Why are 19" a "stupid" idea? I installed a set of 19" Carlsson Design 1/6 Evo's with P-Zero 245/35-19 and 275/30-19 and have been quite surprised at how little the ride has suffered in my E430 while the traction has greatly improved compared to stock. No rubbing at all with this combination either.

Anyway, it seems to me that the proper inflation pressures would vary depending on whether the tires are the same size all around or whether the rears are larger (i.e. E55, my combo). Front/rear pressures are one of the variables that affect oversteer vs. understeer. The proper way to get the tire pressures would be to use a pyrometer but I don't think anyone has race-prepped a nearly-stock E-class sedan, have they?

The feature to keep an eye on is the load index of the tire. Since the car is supported by (primarily) the air inside the tire pressure is important. (run flat and SSS tires non-wistanding) A tire with a rated load index lower than stock will require more pressure than OEM applications. Since 99% of people go to something bigger/wider than stock, that most likely has a higher load index, you can play around with pressures until you find a combination that suits your taste. To a small degree you can change the understeer/oversteer balance of your car but most MB have so much understeer dialed in you wont be able to overcome it with tire pressure alone. (note: ESP makes for artificially neutral handling with individual wheel control so forget about trying to tune in under/oversteer on ESP equipped models. ASR has always prevented oversteer but ESP goes several steps further) One of those active pressure monitoring systems might be an interesting addition but I have yet to see one in use. RAE190 has talked about using a setup like that but I have not heard from him how he likes it?

Lee

Dear Lee

You mention most Mercedes have a lot of oversteer dialed in. Which ones don't? I wonder about my '85 500SL AMG (Euro) because I have only had the rear end break loose. (I am not a very fast driver).

Didn't AMG use a heavier front sway bar? I am very curious. Is there any way to tell what suspension components were used? Very curious.

Steve

Steve,
In my experience, most MB have lots of under-steer stock. (the front end "plows" first) This can be overcome with throttle and steering inputs but inherently most MB cars seem to plow/understeer rather than fishtail. Worn suspension components and other changes non-wistanding of course...

You could check your suspension components and see if any PN's are on them. A call to an AMG distributor that knows his history would be of even more use. You might want to call Eddy Lai on that one. www.performances.com (http://www.performances.com)

Hope this helps...Lee