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Old 06-20-2003, 12:41 PM
Duke2.6 Duke2.6 is offline
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Join Date: Mar 2003
Location: Southern California
Posts: 2,055

The original size was 195/65, I now have 205/60 tires. Is there a need to compensate for this difference? [/B]
Increase two to three psi because the load capacity of a 205/60 is about ten percent less than a 195/65. A better sixty series size for the 300E is 215/60 because it has about the same load capacity as the OEM 195/65s. Also, consider that tires normally loose about one to two psi per month, so if you set them low, they could bleed down to an unsafe level if you are not in the habit of checking them at least every month.

OEM pressure recommendations are for the "average" driver and conditions, and tend to be biased towards low pressure for good ride quality. Higher pressures will lower tire operating temperatures, which increases the safety margin at a given load, decreases tire wear, crisps up the steering response, and increases limit handling.

The OEM pressure recommendation for my '88 190E 2.6 is 26/29 and the 185/65VR-15 tires are placarded at 44 psi max cold pressure. I ran them at 42/36 to improve handling and reduce understeer, but it still didn't handle as well as my '84 2.3 due to the higher front weight bias.

I now have 6.5" 300E wheels with 205/55ZR-15 Dunlop Sport 8000s and run them at 36/32 cold pressure. This size has the same load capacity as the OEM 185/65s.

Regardless of pressure, the fronts will tend to wear more on the shoulders and the rears will tend to wear more in the centers, but this can be evened out with a proper tire rotation schedule. If you run low pressure and drive fairly aggresively overall wear and front shoulder/rear center wear will accelerate.

Lower pressure improves ride at the expense of almost everything else including safety, so it depends on your preferences. In my case, crisp handling and the other benefits of high pressure take precedence over ride quality.


Last edited by Duke2.6; 06-20-2003 at 12:55 PM.
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