Purchased new Pirrelli PZero Nero M+S tires for a 2005 E500 4Matic Wagon. Recent service included tire balancing and rotation. A rotational noise at 15mph to 20mph appeared after service in driver side front tire. This tire has 3+ heavy weights on it after recent dealer balancing. Took back the car to dealer for diagnostic on noise. Told tires were cupped and need to replace all 4. Told the Pirellis were not approved for car. Question: are the Pirellis not approved for this car? Would these tires cause cupping? and why would 3+ weights be required for balancing? Many thanks.

Are you talking about a Mercedes dealer or a tire dealer? How many miles on the car? If you've got over 50,000 I'd get a four wheel alignment at the MB dealership. This is the best way to have the suspension carefully inspected and worn parts diagnosed. This is what's usually behind cupping.

It is possible that a poor quality tire won't balance and will also cause cupping. I wouldn't expect these tires to be in that category, put it's possible the 4MATIC doesn't "like" them for some reason. But I'd certainly have the suspension inspected via a 4-wheel alignment.

Thanks for the reply. The original Pirellis were sold and mounted by a Mercedes dealer. The recent service (balance and rotation) was performed by a different Mercedes dealer. The noise appeared after the recent service. The diagnosis was cupped tires. The recommendation was to replace all 4. The reason for cupping was that the Pirellis are not approved for this vehicle. Any help on putting this together would be useful.

If it were my car, I'd probably bite the bullet and replace the tires with one of the OEM-recommended ones. Different tires have different affinities for suspensions, and four-wheel drive isetups are especially sensitive. MB really does test all approved tires with the cars they're matched to. That doesn't mean that a different tire won't work well, but you don't have the same level of assurance.

If one MB dealer is telling you the tires that another MB sold your are not appropriate, I'd complain to the "zone," the regional MB service organization. I wouldn't waste my time trying to get either dealer to help you out, but I'd call 1-800-FOR-MERC and tell them you are caught between two dealers and want to escalate the complaint to the zone. Hopefully you can get some help toward the new tires. You might also pursue the warranty that came with the tires.

Another hint: don't rotate your tires. The wear patterns are so different front to back that you'll get more satisfying performance and just about the same life anyway if you leave them alone. You might have to replace the rears more often, but in the long run you'll spend as much and won't have to deal with unhappy tires as often.

In most cases cupping on tires is caused by under inflation although alignment could be a factor.

Very important...when you get the new tires, ensure that they perform a dynamic balance and a road force test. I have found some dealers (Lokey Mercedes) have the equipment but don't use it properly. You might fake innocent curiousity and ask if you can watch them do the work.

This is a well traveled road for me changing tires (4 sets in 75000 miles) every 15000 miles or so for cupping and alignments. I found that Michelins and Conti's that came on the car work well, wear even and don't cup. However every other tire I have used cupped and made noise so loud I could not hear the radio.

There is a difference IMO in how the tires are made in the belts. Michelin and Conti's use a seamless method and the other makers use a splice. Check the side walls and see if the tires you use are made in Japan. I found many were and IMO they are made in the same factory but different mold so the technology will be the same regardless of the name. The Michelins and Conti's are made in Germany or US and they work well. The $$ saved on the other tires is lost when you have to pull them early. We put them on a race car to use them up after I pulled them off. So regardless what the dealer sells, look at what is on the new cars on the show room floor, buy that brand. MY reco.. stay away from others on MB's.

I did find one thing that helped. Increase tire pressure to 35 psi to lift the outside tread a bit and this will help some to extend the life of the tires you are running. But they will ride harsher and wear out faster than had it worn even.

Excellent suggestion!!