Hi- New to the forum and new Mercedes owner. Actually my wife is the Mercedes owner as I drive my '02 BMW M3 but she foolishly leaves all car issues in my hands. So the '06 was purchased by her this last July with 28K miles on the clock. At purchase the car was given a new set of rear Michelin Primacy Pilot Sport tires in the 245/40 R17 size to match the front Primacy OEM tires. The car has a staggered set up as I'm sure you guys know.
Now, with 39K on the clock we are shocked to find that the rear tires are not only in need of replacement, but I can actually see the cords of the tire through what is left of the tire. I mean there is not a single hint of tread across the face of either tire in the rear, total slicks!! That's 11k miles and they probably should have been changed 2k miles ago when the wear bars were still there to look at.
Frankly, I have driven what I consider high performance cars that are hell on rear tires. An 88 M6, a 99 M3 and now my '02 M3 which all have, until now, been the fastest eater of rear tires I have ever seen. But I get 20-25K miles on these car's rear tires and my current car runs 275/30 R18 on the back with over 20K miles and I drive pretty spirited. But I do not drive this Mercedes, my wife does and she is way nicer to tires than I. This is a pretty tame 2.3 liter engine, so its not a burn out machine for sure.
The dealer claims this is normal wear for tires but I am making him do a 4 wheel alignment anyways. I am just wondering if this really is normal? I drive Michelin Pilot Sports on the BMW and always felt I got good wear. The Primacy is rated similar in the wear rating dept but 10K for a set at what they cost are pathetic.
I will be replacing all four tires in the spring when I take the Winter wheels and tires I am about to mount on the car off. I guess the Primacy is not a tire I will choose but frankly I am wondering if its the nature of the car to get this low wear from the backs or if I go with a different tire I can hope to increase the lifespan. If its the nature of the beast on this car, I will pick a cheaper tire and just wonder how such a low horsepower mild suspension car can eat tires like this.

 

That sounds like normal wear for summer tires. I have 05 C230k with 28k miles and I am on my third set of rear tires. They seem to last about 12k miles. I had an E36 M3, and I was lucky to get 10k miles out of a set of tires. 25k miles for rear tires on an M3 is unheard of, for me at least. I drive pretty hard... no burnouts though.

 

Your tires are only lasting 12k because they are racing/high-performance tires with very soft tread. Do you race the car? Look on the side of your tire at the treadwear rating; it is probably 180 or 220, which means very short life. It is interesting that they put the fastest wearing tires on your car, and then you have to buy tires twice a year. And also putting the wheels on and off the tire machine so many times accelerates dents and scratches to the wheels and car.

Why not try the "Michelin pilot sport A/S"? It has 400 treadwear rating, harder rubber, and lasts most people three years. A/S stands for all-season.It's not a racing tire, but it is great for the highway, street, and normal driving. I think the price is a bit lower also.

Blue

 

Agree with BlueS....switch to an all-season, "harder" tire and see more treadwear. That's the only answer. It's not the alignment.
It's the tire. My Michelin Pilot Sports wore out faster than Grant took Richmond. Now I use BF Goodrich G-Force. Better, but no mileage
champ for the rears for sure. You can always go to www.tirerack.com and read the reviews people write for every single tire for your car.
Also, treadwear comments by owners. Interesting. I'm sure you know about this if you drive an M3.

If you think the tires wear out fast, take a peek at the front rotors now and then.

Ha!

 

It is a trade off. Summer tires have awesome grip and are a blast to drive on. But they wear fast because they are soft, and they don't work at all in snow and work very poorly in freezing temps. I live in an area where it doesn't get cold, and I choose to run summer tires year round because they are more fun. All season tires can last much longer, but you sacrifice the ultimate grip that you can only get with ultra high or max performance summer tires.