Ride Improvement

[zafarhayatkhan]

I had installed new tires from the TireRack physical location in Indiana during a winter storm a few months back.

I checked the pressure today, it was 36 psi. Reduced it to 27 and the ride is very different from what it was!! Very smooth and comfortable, yet controlled, just like it should be in a Mercedes Benz.

[manny]

What is the mfg's recommendation for your car ?

[haasman]

Zafar

Be sure to inflate your tires to at least what is recommended by Mercedes. You can find the inflation information under your fuel filler door.

Under inflated tires wear more quickly and can actually be dangerous.

Keep us posted,

Haasman

[Mel Weaver]

Be sure to check "cold" air press. , 27 seems awfully low!
As previously posted-check recommended press.
I.M.H.O. You may want to bump press. by at least 2 lbs. over recommended pressure. ( at least!)
-M
"cushy" or "spirited"?


P.S. Is there a spell check here?!!!! Vocab. doesn't equal spelling skills!

[PaulG]

zafarhayatkhan,

Keep an eye on the tyre temperatures and wear patterns.

My guess is that they would ovearheat and wear on the outer edges of the tread.

If they don't, and you are happy with the extra roll and lower grip, you may well have discovered the cheapest tuning mod ever

[zafarhayatkhan]

The inflation information on the fuel door for my 94 E320 is as follows:
Normal Load: 27 Front 27 Rear

Maximum Load: 28 Front 33 Rear

Over 100 mph: +8


The original size was 195/65, I now have 205/60 tires. Is there a need to compensate for this difference?

[Duke2.6]

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.

Duke

[zafarhayatkhan]

Thanks Duke. 30 seems like a good number. What is the resoning behind different front and rear pressures? I thought these car had an almost 50/50 balance.

Very high tire pressures would increase the stress on the structure and body due to less absorbtion of impacts by the tire, but on the other hand, W124 structure is very strong!!

In other vehicles, this could lead to rattles and other concerns.

[Duke2.6]

My 2.6 is about 57 percent front heavy compared to about 52 (maybe 54) for the '84 2.3, so the 2.6 has more inherent understeer. I run front pressure bias to mitigate it as much as possible. The 300E has better balance than the 2.6, so equal pressure would probably be acceptable. Within limits, tire pressure is a "tuning" issue to get the best ride/handling compromise for each individual. It's a matter of experimentation to determine what is best for you.

I consider OEM recommendations to be absolute minimums biased toward ride quality. It safe to run cold pressure as high as the maximum cold pressure placarded on the sidewall, but this is not necessarily the pressure for best handling as I found out a week ago when I almost spun my MR2 after forgeting to lower the cold pressure to 32 from the 37 they had bled down to from the 40 I set prior to winter storage. As a rule of thumb, the lower a tire is actually loaded relative to its maximum load capacity, the less pressure it needs for optimum handling.

Shorter sidewall tires and higher tire pressure will tranmit more high frequency input from the road to the body that the occupants can "hear" and "feel", but the thumping, buzzing, and rattling won't affect the structual integrity of the body. Those are just trim pieces moving around and maybe a little body resonance if the input is in the range of 15-25 Hertz.

Duke

[haasman]

All very interesting until one loads the car: passengers and luggage. Then one sees the front to rear ratio change significantly. Look again at the recommended pressures for loads.

In a nutshell, with increased loads the rear tire pressure goes up, independently of where the front preference is.

Haasman

Without running out to the car in the rain right nowto check, I believe my wagon gas flap says 28 front and 32 rear (light load)- right Hassman, you've got a W124 wagon too?